National Library of Energy BETA

Sample records for flared processing losses

  1. Reduction of Hydrocarbon Losses to Flare Systems 

    E-Print Network [OSTI]

    Page, J.

    1979-01-01

    action to minimize hydrocarbon releases, 2) install flare gas recovery systems, and 3) recover or reduce process streams which have to be continuous1y vented to the flare system. This report discusses alternate designs for flare gas monitoring and flare...

  2. Connecting Flares and Transient Mass Loss Events in Magnetically Active Stars

    E-Print Network [OSTI]

    Osten, Rachel A

    2015-01-01

    We explore the ramification of associating the energetics of extreme mag- netic reconnection events with transient mass loss in a stellar analogy with solar eruptive events. We establish energy partitions relative to the total bolometric radiated flare energy for different observed components of stellar flares, and show that there is rough agreement for these values with solar flares. We apply an equipartition between the bolometric radiated flare energy and kinetic energy in an accompanying mass ejection, seen in solar eruptive events and expected from reconnection. This allows an integrated flare rate in a particular waveband to be used to estimate the amount of associated transient mass loss. This approach is supported by a good correspondence between observational flare signatures on high flaring rate stars and the Sun, which suggests a common physical origin. If the frequent and extreme flares that young solar-like stars and low-mass stars experience are accompanied by transient mass loss in the form of ...

  3. Empirical Determination of the Energy Loss Rate of Accelerated Electrons in a Well-Observed Solar Flare

    E-Print Network [OSTI]

    Piana, Michele

    & Michele Piana1,3 ABSTRACT We present electron images of an extended solar flare source, deduced from the impulsive phase of a solar flare typically appears in the form of accelerated electrons. In the generallyEmpirical Determination of the Energy Loss Rate of Accelerated Electrons in a Well-Observed Solar

  4. Automatic Solar Flare Tracking Using Image Processing Qu Ming and Shih Frank (shih@njit.edu)

    E-Print Network [OSTI]

    Automatic Solar Flare Tracking Using Image Processing Techniques Qu Ming and Shih Frank (shih Abstract. Measurement of the evolution properties of solar flares through their complete cyclic development the properties of solar flares. We also present our solution for automatically tracking the apparent separation

  5. Solar Flare Tracking Using Image Processing Techniques , Frank Y. Shih1

    E-Print Network [OSTI]

    Solar Flare Tracking Using Image Processing Techniques Ming Qu1 , Frank Y. Shih1 , Ju Jing2 grants IIS-0324816, ATM 0233931 and ATM 0313591. Abstract. Automatic property measurement of solar flares through their complete cyclic development is valuable in the studies of solar flares. From the analysis

  6. UNDERSTANDING THE IMPACT OF RETURN-CURRENT LOSSES ON THE X-RAY EMISSION FROM SOLAR FLARES

    SciTech Connect (OSTI)

    Holman, Gordon D., E-mail: Gordon.D.Holman@nasa.gov [NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States)

    2012-01-20

    I obtain and examine the implications of one-dimensional analytic solutions for return-current losses on an initially power-law distribution of energetic electrons with a sharp low-energy cutoff in flare plasma with classical (collisional) resistivity. These solutions show, for example, that return-current losses are not sensitive to plasma density, but are sensitive to plasma temperature and the low-energy cutoff of the injected nonthermal electron distribution. A characteristic distance from the electron injection site, x{sub rc}, is derived. At distances less than x{sub rc} the electron flux density is not reduced by return-current losses, but plasma heating can be substantial in this region, in the upper, coronal part of the flare loop. Before the electrons reach the collisional thick-target region of the flare loop, an injected power-law electron distribution with a low-energy cutoff maintains that structure, but with a flat energy distribution below the cutoff energy, which is now determined by the total potential drop experienced by the electrons. Modifications due to the presence of collisional losses are discussed. I compare these results with earlier analytical results and with more recent numerical simulations. Emslie's conjecture that there is a maximum integrated X-ray source brightness on the order of 10{sup -15} photons cm{sup -2} s{sup -1} cm{sup -2} is examined. I find that this is not actually the maximum brightness and its value is parameter dependent, but it is nevertheless a valuable benchmark for identifying return-current losses in hard X-ray spectra. I discuss an observational approach to identifying return-current losses in flare data, including identification of a return-current 'bump' in X-ray light curves at low photon energies.

  7. Reducing Safety Flaring through Advanced Control 

    E-Print Network [OSTI]

    Hokanson, D.; Lehman, K.; Matsumoto, S.; Takai, N.; Takase, F.

    2010-01-01

    An advanced process control application, using DMCplus® (Aspen Technology, Inc.), was developed to substantially reduce fuel gas losses to the flare at a large integrated refining / petrochemical complex. Fluctuations in internal fuel gas system...

  8. Brightest Fermi-LAT flares of PKS 1222+216: implications on emission and acceleration processes

    SciTech Connect (OSTI)

    Kushwaha, Pankaj; Singh, K. P.; Sahayanathan, Sunder

    2014-11-20

    We present a high time resolution study of the two brightest ?-ray outbursts from a blazar PKS 1222+216 observed by the Fermi Large Area Telescope (LAT) in 2010. The ?-ray light curves obtained in four different energy bands, 0.1-3, 0.1-0.3, 0.3-1, and 1-3 GeV, with time bins of six hours, show asymmetric profiles with similar rise times in all the bands but a rapid decline during the April flare and a gradual one during the June flare. The light curves during the April flare show an ?2 day long plateau in 0.1-0.3 GeV emission, erratic variations in 0.3-1 GeV emission, and a daily recurring feature in 1-3 GeV emission until the rapid rise and decline within a day. The June flare shows a monotonic rise until the peak, followed by a gradual decline powered mainly by the multi-peak 0.1-0.3 GeV emission. The peak fluxes during both the flares are similar except in the 1-3 GeV band in April, which is twice the corresponding flux during the June flare. Hardness ratios during the April flare indicate spectral hardening in the rising phase followed by softening during the decay. We attribute this behavior to the development of a shock associated with an increase in acceleration efficiency followed by its decay leading to spectral softening. The June flare suggests hardening during the rise followed by a complicated energy dependent behavior during the decay. Observed features during the June flare favor multiple emission regions while the overall flaring episode can be related to jet dynamics.

  9. Solar-type Magnetic Reconnection Model for Magnetar Giant Flare

    E-Print Network [OSTI]

    Youhei Masada; Shigehiro Nagataki; Kazunari Shibata; Toshio Terasawa

    2010-05-24

    We present a theoretical model describing magnetar giant flares on the basis of solar flare/coronal mass ejection theory. In our model, a preflare activity plays a crucial role in driving evaporating flows and supplying baryonic matters into the magnetosphere. The loaded baryonic matter, that is called "prominence", is then gradually uplifted via crustal cracking with maintaining a quasi-force-free equilibrium of the magnetosphere. Finally the prominence is erupted by the magnetic pressure force due to the loss of equilibrium triggered by the explosive magnetic reconnection. The giant flare should be induced as a final outcome of the prominence eruption accompanied by large-scale field reconfigurations. An essential difference between solar and magnetar flares is the control process of their evolutionary dynamics. The flaring activity on magnetars is mainly controlled by the radiative process unlike the solar flare governed by the electron conduction. It is highly suggestive that our model is accountable for the physical properties of the extraordinary giant flare observed on 2004 December 27 from SGR1806-20, including the source of baryonic matters loaded in the expanding ejecta observed after the giant burst.

  10. Evolution of the Loop-Top Source of Solar Flares--Heating and Cooling Processes

    E-Print Network [OSTI]

    Yan Wei Jiang; Siming Liu; Wei Liu; Vahe Petrosian

    2005-08-24

    We present a study of the spatial and spectral evolution of the loop-top (LT) sources in a sample of 6 flares near the solar limb observed by {\\it RHESSI}. A distinct coronal source, which we identify as the LT source, was seen in each of these flares from the early ``pre-heating'' phase through the late decay phase. Spectral analyses reveal an evident steep power-law component in the pre-heating and impulsive phases, suggesting that the particle acceleration starts upon the onset of the flares. In the late decay phase the LT source has a thermal spectrum and appears to be confined within a small region near the top of the flare loop, and does not spread throughout the loop, as is observed at lower energies. The total energy of this source decreases usually faster than expected from the radiative cooling but much slower than that due to the classical Spitzer conductive cooling along the flare loop. These results indicate the presence of a distinct LT region, where the thermal conductivity is suppressed significantly and/or there is a continuous energy input. We suggest that plasma wave turbulence could play important roles in both heating the plasma and suppressing the conduction during the decay phase of solar flares. With a simple quasi-steady loop model we show that the energy input in the gradual phase can be comparable to that in the impulsive phase and demonstrate how the observed cooling and confinement of the LT source can be used to constrain the wave-particle interaction.

  11. Observational evidence for return currents in solar flare loops

    E-Print Network [OSTI]

    Marina Battaglia; Arnold O. Benz

    2008-06-11

    Context: The common flare scenario comprises an acceleration site in the corona and particle transport to the chromosphere. Using satellites available to date it has become possible to distinguish between the two processes of acceleration and transport, and study the particle propagation in flare loops in detail, as well as complete comparisons with theoretical predictions. Aims: We complete a quantitative comparison between flare hard X-ray spectra observed by RHESSI and theoretical predictions. This enables acceleration to be distinguished from transport and the nature of transport effects to be explored. Methods: Data acquired by the RHESSI satellite were analyzed using full sun spectroscopy as well as imaging spectroscopy methods. Coronal source and footpoint spectra of well observed limb events were analyzed and quantitatively compared to theoretical predictions. New concepts are introduced to existing models to resolve discrepancies between observations and predictions. Results: The standard thin-thick target solar flare model cannot explain the observations of all events. In the events presented here, propagation effects in the form of non-collisional energy loss are of importance to explain the observations. We demonstrate that those energy losses can be interpreted in terms of an electric field in the flare loop. One event seems consistent with particle propagation or acceleration in lower than average density in the coronal source. Conclusions: We find observational evidence for an electric field in flare loops caused by return currents.

  12. Energy Loss in Nuclear Drell-Yan Process

    E-Print Network [OSTI]

    Jian-Jun Yang; Guang-Lie Li

    1998-05-21

    By means of the nuclear parton distributions which can be used to provide a good explanation for the EMC effect in the whole x range, we investigate the energy loss effect in nuclear Drell-Yan process. When the cross section of lepton pair production is considered varying with the center-of-mass energy of the nucleon-nucleon collision, we find that the nuclear Drell-Yan(DY) ratio is suppressed due to the energy loss, which balances the overestimate of the DY ratio only in consideration of the effect of nuclear parton distributions.

  13. Is FLARE for Solar flare?

    E-Print Network [OSTI]

    D. Fargion

    2005-12-07

    The Fermi Lab Liquid ARgon experiment, FLARE, a huge neutrino argon-liquid project detector of 50 kt mass, might in a near future enlarge the neutrino telescope accuracy revealing in detail solar, supernova, atmospheric as well as largest solar flares neutrino. Indeed the solar energetic (E_p > 100 MeVs) flare particles (protons, alpha) while scattering among themselves or hitting the solar atmosphere must produce on sun prompt charged pions, whose decay (as well as their sequent muon decays) into secondaries is source of a copious solar neutrino "flare" (at tens or hundreds MeV energy). These brief (minutes) neutrino "burst" at largest flare peak may overcome by three to five order of magnitude the steady atmospheric neutrino noise on the Earth, possibly leading to their emergence and detection above the thresholds. The largest prompt "burst" solar neutrino flare may be detected in future FLARE neutrino detectors both in electron and positron and possibly in its muon pair neutrino component. Our estimate for the recent and exceptional October - November 2003 solar flares and last January 20th 2005 exceptional flare might lead to a few events for future FLARE or near unity for present Super-KamiokandeII. The neutrino spectra may reflect the neutrino flavor oscillations and mixing in flight. In neutrino detectors a surprising (correlated) muon appearance may occur while a rarer tau appearance may even marginally take place. A comparison of the solar neutrino flare signal with other neutrino foreground is estimated: it offer the first opportunity for an independent road map to disentangle the neutrino flavor puzzles, as well a prompt alarm system for dangerous solar flare eruptions.

  14. Flare processes evolution and polarization changes of fine structures of solar radio emission in the April 11, 2013 event

    E-Print Network [OSTI]

    Chernov, Gennady; Tan, Baolin; Yan, Yihua; Tan, Chengming; Fu, Qijun; Karlicky, Marian; Fomichev, Valery

    2015-01-01

    The measurement of positions and sizes of radio sources in the observations of solar radio spectral fine structures in an M6.5 flare on April 11, 2013 were observed simultaneously by several radio instruments at four different observatories: Chinese Solar Broadband Radio Spectrometers at Huairou (SBRS/Huairou), Ondrejov Radio spectrograph in the Czech Republic (ORSC/Ondrejov), Badary Broadband Microwave spectropolarimeter (BMS/Irkutsk), and spectrograph/IZMIRAN (Moscow, Troitsk). The fine structures include microwave zebra patterns (ZP), fast pulsations, and fibers. They were observed during the flare brightening located at the tops of a loop arcade. The dynamics of the polarization was associated with the motion of the flare exciter, which was observed in EUV images at 171A and 131A (SDO/AIA). Combining magnetograms observed by the SDO Helioseismic and Magnetic Imager (HMI) with the homologous assumption of EUV flare brightening and ZP bursts, we deduced that the observed ZPs correspond to the ordinary radio...

  15. EMITTING ELECTRONS SPECTRA AND ACCELERATION PROCESSES IN THE JET OF Mrk 421: FROM THE LOW STATE TO THE GIANT FLARE STATE

    SciTech Connect (OSTI)

    Yan Dahai; Zhang Li; Fan Zhonghui; Zeng Houdun [Department of Physics, Yunnan University, Kunming 650091, Yunnan (China); Yuan Qiang, E-mail: lizhang@ynu.edu.cn [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2013-03-10

    We investigate the electron energy distributions (EEDs) and the acceleration processes in the jet of Mrk 421 through fitting the spectral energy distributions (SEDs) in different active states in the frame of a one-zone synchrotron self-Compton model. After assuming two possible EEDs formed in different acceleration models: the shock-accelerated power law with exponential cut-off (PLC) EED and the stochastic-turbulence-accelerated log-parabolic (LP) EED, we fit the observed SEDs of Mrk 421 in both low and giant flare states using the Markov Chain Monte Carlo method which constrains the model parameters in a more efficient way. The results from our calculations indicate that (1) the PLC and LP models give comparably good fits for the SED in the low state, but the variations of model parameters from low state to flaring can be reasonably explained only in the case of the PLC in the low state; and (2) the LP model gives better fits compared to the PLC model for the SED in the flare state, and the intra-day/night variability observed at GeV-TeV bands can be accommodated only in the LP model. The giant flare may be attributed to the stochastic turbulence re-acceleration of the shock-accelerated electrons in the low state. Therefore, we may conclude that shock acceleration is dominant in the low state, while stochastic turbulence acceleration is dominant in the flare state. Moreover, our result shows that the extrapolated TeV spectra from the best-fit SEDs from optical through GeV with the two EEDs are different. It should be considered with caution when such extrapolated TeV spectra are used to constrain extragalactic background light models.

  16. Method for reducing iron losses in an iron smelting process

    DOE Patents [OSTI]

    Sarma, Balu (Airmont, NY); Downing, Kenneth B. (Greenville, SC)

    1999-01-01

    A process of smelting iron that comprises the steps of: a) introducing a source of iron oxide, oxygen, nitrogen, and a source of carbonaceous fuel to a smelting reactor, at least some of said oxygen being continuously introduced through an overhead lance; b) maintaining conditions in said reactor to cause (i) at least some of the iron oxide to be chemically reduced, (ii) a bath of molten iron to be created and stirred in the bottom of the reactor, surmounted by a layer of slag, and (iii) carbon monoxide gas to rise through the slag; c) causing at least some of said carbon monoxide to react in the reactor with the incoming oxygen, thereby generating heat for reactions taking place in the reactor; and d) releasing from the reactor an offgas effluent, is run in a way that keeps iron losses in the offgas relatively low. After start-up of the process is complete, steps (a) and (b) are controlled so as to: e) keep the temperature of the molten iron at or below about 1550.degree. C. and f) keep the slag weight at or above about 0.8 tonne per square meter.

  17. Cryogenic loss monitors with FPGA TDC signal processing

    SciTech Connect (OSTI)

    Warner, A.; Wu, J.; /Fermilab

    2011-09-01

    Radiation hard helium gas ionization chambers capable of operating in vacuum at temperatures ranging from 5K to 350K have been designed, fabricated and tested and will be used inside the cryostats at Fermilab's Superconducting Radiofrequency beam test facility. The chamber vessels are made of stainless steel and all materials used including seals are known to be radiation hard and suitable for operation at 5K. The chambers are designed to measure radiation up to 30 kRad/hr with sensitivity of approximately 1.9 pA/(Rad/hr). The signal current is measured with a recycling integrator current-to-frequency converter to achieve a required measurement capability for low current and a wide dynamic range. A novel scheme of using an FPGA-based time-to-digital converter (TDC) to measure time intervals between pulses output from the recycling integrator is employed to ensure a fast beam loss response along with a current measurement resolution better than 10-bit. This paper will describe the results obtained and highlight the processing techniques used.

  18. The Origin of the Solar Flare Waiting-Time Distribution

    E-Print Network [OSTI]

    M. S. Wheatland

    2000-05-08

    It was recently pointed out that the distribution of times between solar flares (the flare waiting-time distribution) follows a power law, for long waiting times. Based on 25 years of soft X-ray flares observed by Geostationary Operational Environmental Satellite (GOES) instruments it is shown that 1. the waiting-time distribution of flares is consistent with a time-dependent Poisson process, and 2. the fraction of time the Sun spends with different flaring rates approximately follows an exponential distribution. The second result is a new phenomenological law for flares. It is shown analytically how the observed power-law behavior of the waiting times originates in the exponential distribution of flaring rates. These results are argued to be consistent with a non-stationary avalanche model for flares.

  19. Process and design techniques for low loss integrated silicon photonics

    E-Print Network [OSTI]

    Sparacin, Daniel Knight

    2006-01-01

    Microprocessors have truly revolutionized the efficiency of the world due to the high-volume and low-cost of complimentary metal oxide semiconductor (CMOS) process technology. However, the traditional scaling methods by ...

  20. 2D MHD and 1D HD models of a solar flare -- a comprehensive comparison of the results

    E-Print Network [OSTI]

    Falewicz, R; Murawski, K; Srivastava, A K

    2015-01-01

    Without any doubt solar flaring loops possess a multi-thread internal structure that is poorly resolved and there are no means to observe heating episodes and thermodynamic evolution of the individual threads. These limitations cause fundamental problems in numerical modelling of flaring loops, such as selection of a structure and a number of threads, and an implementation of a proper model of the energy deposition process. A set of 1D hydrodynamic and 2D magnetohydrodynamic models of a flaring loop are developed to compare energy redistribution and plasma dynamics in the course of a prototypical solar flare. Basic parameters of the modeled loop are set according to the progenitor M1.8 flare recorded in the AR10126 on September 20, 2002 between 09:21 UT and 09:50 UT. The non-ideal 1D models include thermal conduction and radiative losses of the optically thin plasma as energy loss mechanisms, while the non-ideal 2D models take into account viscosity and thermal conduction as energy loss mechanisms only. The 2...

  1. Submitted to Ap.J. A Model of Solar Flares and Their Homologous Behavior

    E-Print Network [OSTI]

    Submitted to Ap.J. A Model of Solar Flares and Their Homologous Behavior G. S. Choe and C. Z. Cheng@pppl.gov ABSTRACT A model describing physical processes of solar flares and their homologous behavior is presented. #12; -- 2 -- Subject headings: Sun: flares, MHD, methods: numerical 1. INTRODUCTION Solar flares

  2. Submitted to Ap.J. A Model of Solar Flares and Their Homologous Behavior

    E-Print Network [OSTI]

    Submitted to Ap.J. A Model of Solar Flares and Their Homologous Behavior G. S. Choe and C. Z. Cheng@pppl.gov ABSTRACT A model describing physical processes of solar flares and their homologous behavior is presented. #12;­ 2 ­ Subject headings: Sun: flares, MHD, methods: numerical 1. INTRODUCTION Solar flares

  3. Cryogenic loss monitors with FPGA TDC signal processing

    E-Print Network [OSTI]

    Warner, A

    2012-01-01

    Radiation hard helium gas ionization chambers capable of operating in vacuum at temperatures ranging from 5K to 350K have been designed, fabricated and tested and will be used inside the cryostats at Fermilab's Superconducting Radiofrequency beam test facility. The chamber vessels are made of stainless steel and all materials used including seals are known to be radiation hard and suitable for operation at 5K. The chambers are designed to measure radiation up to 30 kRad/hr with sensitivity of approximately 1.9 pA/(Rad/hr). The signal current is measured with a recycling integrator current-to-frequency converter to achieve a required measurement capability for low current and a wide dynamic range. A novel scheme of using an FPGA-based time-to-digital converter (TDC) to measure time intervals between pulses output from the recycling integrator is employed to ensure a fast beam loss response along with a current measurement resolution better than 10-bit. This paper will describe the results obtained and highligh...

  4. Location of Narrowband Spikes in Solar Flares

    E-Print Network [OSTI]

    Arnold O. Benz; Pascal Saint-Hilaire; Nicole Vilmer

    2001-12-19

    Narrowband spikes of the decimeter type have been identified in dynamic spectrograms of Phoenix-2 of ETH Zurich and located in position with the Nancay Radioheliograph at the same frequency. The spike positions have been compared with the location of hard X-ray emission and the thermal flare plasma in soft X-rays and EUV lines. The decimetric spikes are found to be single sources located some 20" to 400" away from the flare site in hard or soft X-rays. In most cases there is no bright footpoint nearby. In at least two cases the spikes are near loop tops. These observations do not confirm the widely held view that the spike emission is produced by some loss-cone instability masering near the footpoints of flare loops. On the other hand, the large distance to the flare sites and the fact that these spikes are all observed in the flare decay phase make the analyzed spike sources questionable sites for the main flare electron acceleration. They possibly indicate coronal post-flare acceleration sites.

  5. Lithium-6 from Solar Flares

    E-Print Network [OSTI]

    R. Ramaty; V. Tatischeff; J. P. Thibaud; B. Kozlovsky; N. Mandzhavidze

    2000-03-23

    By introducing a hitherto ignored Li-6 producing process, due to accelerated He-3 reactions with He-4, we show that accelerated particle interactions in solar flares produce much more Li-6 than Li-7. By normalizing our calculations to gamma-ray data we demonstrate that the Li-6 produced in solar flares, combined with photospheric Li-7, can account for the recently determined solar wind lithium isotopic ratio, obtained from measurements in lunar soil, provided that the bulk of the flare produced lithium is evacuated by the solar wind. Further research in this area could provide unique information on a variety of problems, including solar atmospheric transport and mixing, solar convection and the lithium depletion issue, and solar wind and solar particle acceleration.

  6. The local Poisson hypothesis for solar flares

    E-Print Network [OSTI]

    M. S. Wheatland

    2001-07-09

    The question of whether flares occur as a Poisson process has important consequences for flare physics. Recently Lepreti et al. presented evidence for local departure from Poisson statistics in the Geostationary Operational Environmental Satellite (GOES) X-ray flare catalog. Here it is argued that this effect arises from a selection effect inherent in the soft X-ray observations; namely that the slow decay of enhanced flux following a large flare makes detection of subsequent flares less likely. It is also shown that the power-law tail of the GOES waiting-time distribution varies with the solar cycle. This counts against any intrinsic significance to the appearance of a power law, or to the value of its index.

  7. Sauget Plant Flare Gas Reduction Project 

    E-Print Network [OSTI]

    Ratkowski, D. P.

    2007-01-01

    Empirical analysis of stack gas heating value allowed the Afton Chemical Corporation Sauget Plant to reduce natural gas flow to its process flares by about 50% while maintaining the EPA-required minimum heating value of the gas streams....

  8. Loss-Gain Equalized Reconfigurable Phaser for Dynamic Radio Analog Signal Processing (R-ASP)

    E-Print Network [OSTI]

    Zou, Lianfeng; Caloz, Christophe

    2015-01-01

    We present a loss-gain equalized reconfigurable phaser for dynamic radio analog signal processing (R-ASP). Such a phaser provides real-time tunable group delay response with all-pass transmission. We propose a lumped loss-gain implementation, where tuning and equalization are mostly easily achieved. A theoretical study derives the transfer function and the fundamental characteristics of the device. The phaser is finally experimentally demonstrated, first using a single loss-gain pair and finally a three cascaded loss-gain pair structure with full reconfigurability , where up-chirp and down-chirp group delays are shown for illustration. It is expected that this phaser will find wide applications in radio analog signal processing (R-ASP) systems requiring dynamic adaptability.

  9. LOSS OF PLASMA MEMBRANE PROTEINS OF BULL SPERMATOZOA THROUGH THE FREEZING -THAWING PROCESS

    E-Print Network [OSTI]

    Zaragoza, Universidad de

    ELSEVIER LOSS OF PLASMA MEMBRANE PROTEINS OF BULL SPERMATOZOA THROUGH THE FREEZING -THAWING PROCESS that some cell membrane proteins are lost through the freezing-thawing process. © 1998by ElsevierScience Inc of sperm cells, adsorption would probably be more affected at freezing temperatures, since some

  10. Collective Acceleration in Solar Flares

    E-Print Network [OSTI]

    Barletta, W.

    2008-01-01

    Collective Acceleration in Solar Flares w. Barletta, S.S.COLLECTIVE ACCELERATION IN SOLAR FLARES* W. Barletta (1), S.Park, MD 20742 Abstract Solar flare data are examined with

  11. Flare System Optimization 

    E-Print Network [OSTI]

    Aegerter, R.

    2003-01-01

    , steam, nitrogen, and natural gas. By properly operating and maintaining the flare system and with minor improvements, significant savings can be achieved....

  12. Energy Loss Effect in High Energy Nuclear Drell-Yan Process

    E-Print Network [OSTI]

    Chun-Gui Duan; Li-Hua Song; Li-Juan Huo; Guang-Lie Li

    2004-05-13

    The energy loss effect in nuclear matter, which is another nuclear effect apart from the nuclear effect on the parton distribution as in deep inelastic scattering process, can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of the nuclear parton distribution studied only with lepton deep inelastic scattering experimental data, measured Drell-Yan production cross sections for 800GeV proton incident on a variety of nuclear targets are analyzed within Glauber framework which takes into account energy loss of the beam proton. It is shown that the theoretical results with considering the energy loss effect are in good agreement with the FNAL E866.

  13. Estimating Water Quality Pollution Impacts Based on Economic Loss Models in Urbanization Process

    E-Print Network [OSTI]

    Yu, Qian

    Estimating Water Quality Pollution Impacts Based on Economic Loss Models in Urbanization Process Abstract: The study investigates water quality pollution impacts on urbanization by analyzing temporal the greatest contributors of surface water quality pollution from 1996 to 2003. High values existed

  14. Initial Observations of Sunspot Oscillations Excited by Solar Flare

    E-Print Network [OSTI]

    A. G. Kosovichev; T. Sekii

    2007-10-09

    Observations of a large solar flare of December 13, 2006, using Solar Optical Telescope (SOT) on Hinode spacecraft revealed high-frequency oscillations excited by the flare in the sunspot chromosphere. These oscillations are observed in the region of strong magnetic field of the sunspot umbra, and may provide a new diagnostic tool for probing the structure of sunspots and understanding physical processes in solar flares.

  15. Nucleosynthesis in stellar flares

    E-Print Network [OSTI]

    V. Tatischeff; J. -P. Thibaud; I. Ribas

    2008-01-11

    Nuclear interactions of ions accelerated at the surface of flaring stars can produce fresh isotopes in stellar atmospheres. Although this nucleosynthesis is not significant for the chemical evolution of the Galaxy, it can be important for a number of measurements of "anomalously" high 6-Li and 7-Li abundances. We discuss the possible role of stellar flares to explain the recent report of high 6-Li abundances in metal-poor halo stars and the well-established correlation between Li abundance and stellar activity in young open clusters. We then study the possibility of observing directly Li production during flares of nearby and active dwarfs of spectral type M.

  16. Model-Based Control of Nonlinear Systems Subject to Sensor Data Losses: A Chemical Process Case Study

    E-Print Network [OSTI]

    Sontag, Eduardo

    Model-Based Control of Nonlinear Systems Subject to Sensor Data Losses: A Chemical Process Case, Los Angeles, CA 90095-1592, USA, davidmps@ucla.edu, pdc@seas.ucla.edu. Controller Process x Data feedback control of nonlinear uncertain systems subject to sensor data losses. We compare three different

  17. Early Abnormal Temperature Structure of X-ray Looptop Source of Solar Flares

    E-Print Network [OSTI]

    Early Abnormal Temperature Structure of X-ray Looptop Source of Solar Flares Jinhua Shen1 processes in the contraction and expansion phases of these solar flares are different. Subject headings: Sun: activity -- Sun: magnetic reconnection -- Sun: flares 1. Introduction It is widely accepted that solar

  18. PPPL-3450 PPPL-3450 Solar Flare Mechanism Based on Magnetic Arcade

    E-Print Network [OSTI]

    PPPL-3450 PPPL-3450 UC-70 Solar Flare Mechanism Based on Magnetic Arcade Reconnection and Island, 00, 000­000, 2000 Solar Flare Mechanism Based on Magnetic Arcade Reconnection and Island Merging C. Z-0451 (Received ; Revised ; Accepted ) We propose a model describing physical processes of solar flares based

  19. Parameterization of solar flare dose 

    E-Print Network [OSTI]

    Lamarche, Anne Helene

    1995-01-01

    A critical aspect of missions to the Moon or Mars is the safety and health of the crew. Radiation in space is a hazard for astronauts, especially high-energy radiation following certain types of solar flares. A solar flare ...

  20. Size dependence of solar X-ray flare properties

    E-Print Network [OSTI]

    Marina Battaglia; Paolo C. Grigis; Arnold O. Benz

    2005-05-09

    Non-thermal and thermal parameters of 85 solar flares of GOES class B1 to M6 (background subtracted classes A1 to M6) have been compared to each other. The hard X-ray flux has been measured by RHESSI and a spectral fitting provided flux and spectral index of the non-thermal emission, as well as temperature and emission measure of the thermal emission. The soft X-ray flux was taken from GOES measurements. We find a linear correlation in a double logarithmic plot between the non-thermal flux and the spectral index. The higher the acceleration rate of a flare, the harder the non-thermal electron distribution. The relation is similar to the one found by a comparison of the same parameters from several sub-peaks of a single flare. Thus small flares behave like small subpeaks of large flares. Thermal flare properties such as temperature, emission measure and the soft X-ray flux also correlate with peak non-thermal flux. A large non-thermal peak flux entails an enhancement in both thermal parameters. The relation between spectral index and the non-thermal flux is an intrinsic feature of the particle acceleration process, depending on flare size. This property affects the reported frequency distribution of flare energies.

  1. Return currents and energy transport in the solar flaring Anna Codispoti1

    E-Print Network [OSTI]

    Piana, Michele

    Return currents and energy transport in the solar flaring atmosphere Anna Codispoti1 ,Gabriele electrons in solar flares. We first utilize the Rutherford cross-section to derive the formula of the energy for the energy loss rate provides a better fit of the experimental data with respect to the model based

  2. Early Abnormal Temperature Structure of X-ray Looptop Source of Solar Flares

    E-Print Network [OSTI]

    Jinhua Shen; Tuanhui Zhou; Haisheng Ji; Na Wang; Wenda Cao; Haimin Wang

    2008-08-29

    This Letter is to investigate the physics of a newly discovered phenomenon -- contracting flare loops in the early phase of solar flares. In classical flare models, which were constructed based on the phenomenon of expansion of flare loops, an energy releasing site is put above flare loops. These models can predict that there is a vertical temperature gradient in the top of flare loops due to heat conduction and cooling effects. Therefore, the centroid of an X-ray looptop source at higher energy bands will be higher in altitude, for which we can define as normal temperature distribution. With observations made by {\\it RHESSI}, we analyzed 10 M- or X-class flares (9 limb flares). For all these flares, the movement of looptop sources shows an obvious U-shaped trajectory, which we take as the signature of contraction-to-expansion of flare loops. We find that, for all these flares, normal temperature distribution does exist, but only along the path of expansion. The temperature distribution along the path of contraction is abnormal, showing no spatial order at all. The result suggests that magnetic reconnection processes in the contraction and expansion phases of these solar flares are different.

  3. Gamma-ray burst flares: X-ray flaring. II

    SciTech Connect (OSTI)

    Swenson, C. A.; Roming, P. W. A., E-mail: cswenson@astro.psu.edu [Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)

    2014-06-10

    We present a catalog of 498 flaring periods found in gamma-ray burst (GRB) light curves taken from the online Swift X-Ray Telescope GRB Catalogue. We analyzed 680 individual light curves using a flare detection method developed and used on our UV/optical GRB Flare Catalog. This method makes use of the Bayesian Information Criterion to analyze the residuals of fitted GRB light curves and statistically determines the optimal fit to the light curve residuals in an attempt to identify any additional features. These features, which we classify as flares, are identified by iteratively adding additional 'breaks' to the light curve. We find evidence of flaring in 326 of the analyzed light curves. For those light curves with flares, we find an average number of ?1.5 flares per GRB. As with the UV/optical, flaring in our sample is generally confined to the first 1000 s of the afterglow, but can be detected to beyond 10{sup 5} s. Only ?50% of the detected flares follow the 'classical' definition of ?t/t ? 0.5, with many of the largest flares exceeding this value.

  4. The Impulsive Phase in Solar Flares: Recent Multi-wavelength Results and their Implications for Microwave Modeling and Observations

    E-Print Network [OSTI]

    Fletcher, Lyndsay

    2013-01-01

    This short paper reviews several recent key observations of the processes occurring in the lower atmosphere (chromosphere and photosphere) during flares. These are: evidence for compact and fragmentary structure in the flare chromosphere, the conditions in optical flare footpoints, step-like variations in the magnetic field during the flare impulsive phase, and hot, dense 'chromospheric' footpoints. The implications of these observations for microwaves are also discussed.

  5. Thermal and non-thermal energies in solar flares

    E-Print Network [OSTI]

    Pascal Saint-Hilaire; Arnold O. Benz

    2005-03-03

    The energy of the thermal flare plasma and the kinetic energy of the non-thermal electrons in 14 hard X-ray peaks from 9 medium-sized solar flares have been determined from RHESSI observations. The emissions have been carefully separated in the spectrum. The turnover or cutoff in the low-energy distribution of electrons has been studied by simulation and fitting, yielding a reliable lower limit to the non-thermal energy. It remains the largest contribution to the error budget. Other effects, such as albedo, non-uniform target ionization, hot target, and cross-sections on the spectrum have been studied. The errors of the thermal energy are about equally as large. They are due to the estimate of the flare volume, the assumption of the filling factor, and energy losses. Within a flare, the non-thermal/thermal ratio increases with accumulation time, as expected from loss of thermal energy due to radiative cooling or heat conduction. Our analysis suggests that the thermal and non-thermal energies are of the same magnitude. This surprising result may be interpreted by an efficient conversion of non-thermal energy to hot flare plasma.

  6. Solar Flares and particle acceleration

    E-Print Network [OSTI]

    energy ~2 1032 ergs #12;"Standard" model of a solar flare/CME Solar corona T ~ 106 K => 0.1 keV per MeV Proton energies >100 MeV Large solar flare releases about 1032 ergs (about half energy-free emission) #12;X-ray spectrum of solar flares Thermal X-rays Non-thermal X-rays Gamma-ray lines Ramaty High

  7. Interferometric at-wavelength flare characterization of EUV optical systems

    DOE Patents [OSTI]

    Naulleau, Patrick P. (Oakland, CA); Goldberg, Kenneth Alan (Berkeley, CA)

    2001-01-01

    The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) provides the high-accuracy wavefront characterization critical to the development of EUV lithography systems. Enhancing the implementation of the PS/PDI can significantly extend its spatial-frequency measurement bandwidth. The enhanced PS/PDI is capable of simultaneously characterizing both wavefront and flare. The enhanced technique employs a hybrid spatial/temporal-domain point diffraction interferometer (referred to as the dual-domain PS/PDI) that is capable of suppressing the scattered-reference-light noise that hinders the conventional PS/PDI. Using the dual-domain technique in combination with a flare-measurement-optimized mask and an iterative calculation process for removing flare contribution caused by higher order grating diffraction terms, the enhanced PS/PDI can be used to simultaneously measure both figure and flare in optical systems.

  8. Electron Firehose instability and acceleration of electrons in solar flares

    E-Print Network [OSTI]

    Gunnar Paesold; Arnold O. Benz

    2000-01-14

    An electron distribution with a temperature anisotropy T_par/T_perp > 1 can lead to the Electron Firehose instability (Here par and perp denote directions relative to the background magnetic field B_0). Since possible particle acceleration mechanisms in solar flares exhibit a preference of energizing particles in parallel direction, such an anisotropy is expected during the impulsive phase of a flare. The properties of the excited waves and the thresholds for instability are investigated by using linearized kinetic theory. These thresholds were connected to the pre-flare plasma parameters by assuming an acceleration model acting exclusively in parallel direction. For usually assumed pre-flare plasma conditions the electrons become unstable during the acceleration process and lefthand circularly polarized waves with frequencies of about the proton gyrofrequency are excited at parallel propagation. Indications have been found, that the largest growth rates occur at oblique propagation and the according frequencies lie well above the proton gyrofrequency.

  9. Transition Region Emission and Energy Input to Thermal Plasma During the Impulsive Phase of Solar Flares

    E-Print Network [OSTI]

    J. C. Raymond; G. Holman; A. Ciaravella; A. Panasyuk; Y. -K. Ko; J. Kohl

    2007-01-12

    The energy released in a solar flare is partitioned between thermal and non-thermal particle energy and lost to thermal conduction and radiation over a broad range of wavelengths. It is difficult to determine the conductive losses and the energy radiated at transition region temperatures during the impulsive phases of flares. We use UVCS measurements of O VI photons produced by 5 flares and subsequently scattered by O VI ions in the corona to determine the 5.0 thermal energy and the conductive losses deduced from RHESSI and GOES X-ray data using areas from RHESSI images to estimate the loop volumes, cross-sectional areas and scale lengths. The transition region luminosities during the impulsive phase exceed the X-ray luminosities for the first few minutes, but they are smaller than the rates of increase of thermal energy unless the filling factor of the X-ray emitting gas is ~ 0.01. The estimated conductive losses from the hot gas are too large to be balanced by radiative losses or heating of evaporated plasma, and we conclude that the area of the flare magnetic flux tubes is much smaller than the effective area measured by RHESSI during this phase of the flares. For the 2002 July 23 flare, the energy deposited by non-thermal particles exceeds the X-ray and UV energy losses and the rate of increase of the thermal energy.

  10. Historical Processes and Genetic Implications of Limb Reduction and Loss in an Island Skink Lineage

    E-Print Network [OSTI]

    Siler, Cameron David

    2011-12-31

    Evolutionary simplification, or loss of complex characters, is a major theme in studies of body form evolution. The apparently infrequent evolutionary reacquisition of complex characters has led to the assertion (Dollo's ...

  11. The impact of personal gains and losses on social identification processes 

    E-Print Network [OSTI]

    Iuzzini, Jonathan Lawrence

    1998-01-01

    This thesis integrates a number of social ge Micrographics. psychological principles to study individual-level benefit (gain) and discrimination (loss) in a group setting. Using a variation of the minimal group paradigm, participants were assigned...

  12. Return currents and energy transport in the solar flaring atmosphere

    E-Print Network [OSTI]

    Codispoti, Anna; Piana, Michele; Pinamonti, Nicola

    2013-01-01

    According to a standard ohmic perspective, the injection of accelerated electrons into the flaring region violates local charge equilibrium and therefore, in response, return currents are driven by an electric field to equilibrate such charge violation. In this framework, the energy loss rate associated to these local currents has an ohmic nature and significantly shortens the acceleration electron path. In the present paper we adopt a different viewpoint and, specifically, we study the impact of the background drift velocity on the energy loss rate of accelerated electrons in solar flares. We first utilize the Rutherford cross-section to derive the formula of the energy loss rate when the collisional target has a finite temperature and the background instantaneously and coherently moves up to equilibrate the electron injection. We then use the continuity equation for electrons and imaging spectroscopy data provided by RHESSI to validate this model. Specifically, we show that this new formula for the energy l...

  13. A Bayesian Approach to Solar Flare Prediction

    E-Print Network [OSTI]

    M. S. Wheatland

    2004-03-26

    A number of methods of flare prediction rely on classification of physical characteristics of an active region, in particular optical classification of sunspots, and historical rates of flaring for a given classification. However these methods largely ignore the number of flares the active region has already produced, in particular the number of small events. The past history of occurrence of flares (of all sizes) is an important indicator to future flare production. We present a Bayesian approach to flare prediction, which uses the flaring record of an active region together with phenomenological rules of flare statistics to refine an initial prediction for the occurrence of a big flare during a subsequent period of time. The initial prediction is assumed to come from one of the extant methods of flare prediction. The theory of the method is outlined, and simulations are presented to show how the refinement step of the method works in practice.

  14. A SOLAR FLARE MODEL IN BETWEEN MHD AND CELLULAR AUTOMATON* Heinz Isliker1

    E-Print Network [OSTI]

    Anastasiadis, Anastasios

    ) and the reproduction of the observed solar flare statistics. On the other hand the energy release process has been to explain the solar flare statistics derived from observations. These models simulate the storage of this approach is the treatment of a large number of elementary energy release events (avalanches

  15. Filament Eruption after the Onset of the X1.5 Flare on 2005 September 13 Haimin Wang, Chang Liu, Ju Jing, and Vasyl Yurchyshyn

    E-Print Network [OSTI]

    Filament Eruption after the Onset of the X1.5 Flare on 2005 September 13 Haimin Wang, Chang Liu, Ju Erupting filaments usually play the role as the initial driver of flaring process pre- ceding September 13, a filament at the boundary of the NOAA AR 0808 erupted 13 minutes after the flare onset at 19

  16. Looptop Hard X-Ray Emission in Solar Flares: Images and Statistics

    E-Print Network [OSTI]

    Vahe' Petrosian; Timothy Q. Donaghy; James M. McTiernan

    2001-12-14

    The discovery of hard X-ray sources near the top of a flaring loop by the HXT instrument on board the YOHKOH satellite represents a significant progress towards the understanding of the basic processes driving solar flares. In this paper we extend the previous study of limb flares by Masuda (1994) by including all YOHKOH observations up through August 1998. We report that from October 1991 to August 1998, YOHKOH observed 20 X-ray bright limb flares (where we use the same selection criteria as Masuda), of which we have sufficient data to analyze 18 events, including 8 previously unanalyzed flares. Of these 18 events, 15 show detectable impulsive looptop emission. Considering that the finite dynamic range (about a decade) of the detection introduces a strong bias against observing comparatively weak looptop sources, we conclude that looptop emission is a common feature of all flares. We summarize the observations of the footpoint to looptop flux ratio and the spectral indices. We present light curves and images of all the important newly analyzed limb flares. Whenever possible we present results for individual pulses in multipeak flares and for different loops for multiloop flares. We then discuss the statistics of the fluxes and spectral indices of the looptop and footpoint sources taking into account observational selection biases. The importance of these observations (and those expected from the scheduled HESSI satellite with its superior angular spectral and temporal resolution) in constraining acceleration models and parameters is discussed briefly.

  17. RHESSI observation of flare elements

    E-Print Network [OSTI]

    Paolo C. Grigis; Arnold O. Benz

    2006-02-14

    RHESSI observations of elementary flare bursts are presented. These solar flare elements are distinct emission peaks of a duration of some tens of seconds present in the hard X-ray light curves. They are characterized by consistent soft-hard-soft spectral behavior, which can be described in a quantitative way and compared which predictions from acceleration models. A detailed analysis of hard X-ray images for an M5 class flare shows that elementary flare bursts do not occur at distinct locations, but as twin X-ray sources move smoothly along an arcade of magnetic loops. This observation apparently contradicts the predictions of standard translation invariant 2.5-dimensional reconnection models.

  18. Analysis of the working process and mechanical losses in a Stirling engine for a solar power unit

    SciTech Connect (OSTI)

    Makhkamov, K.K.; Ingham, D.B.

    1999-05-01

    In this paper a second level mathematical model for the computational simulation of the working process of a 1-kW Stirling engine has been used and the results obtained are presented. The internal circuit of the engine in the calculation scheme was divided into five chambers, namely, the expansion space, heater, regenerator, cooler and the compression space, and the governing system of ordinary differential equations for the energy and mass conservation were solved in each chamber by Euler`s method. In addition, mechanical losses in the construction of the engine have been determined and the computational results show that the mechanical losses for this particular design of the Stirling engine may be up to 50% of the indicated power of the engine.

  19. Reordering an index to speed query processing without loss of effectiveness.

    E-Print Network [OSTI]

    Hawking, David

    of CO2 emissions. To illustrate the importance o world wide web search engines, a factor of two in query processing effi- ciency could translate

  20. Well-observed dynamics of flaring and peripheral coronal magnetic loops during an M-class limb flare

    SciTech Connect (OSTI)

    Shen, Jinhua; Zhou, Tuanhui; Ji, Haisheng; Feng, Li; Wiegelmann, Thomas; Inhester, Bernd

    2014-08-20

    In this paper, we present a variety of well-observed dynamic behaviors for the flaring and peripheral magnetic loops of the M6.6 class extreme limb flare that occurred on 2011 February 24 (SOL2011-02-24T07:20) from EUV observations by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory and X-ray observations by RHESSI. The flaring loop motion confirms the earlier contraction-expansion picture. We find that the U-shaped trajectory delineated by the X-ray corona source of the flare roughly follows the direction of a filament eruption associated with the flare. Different temperature structures of the coronal source during the contraction and expansion phases strongly suggest different kinds of magnetic reconnection processes. For some peripheral loops, we discover that their dynamics are closely correlated with the filament eruption. During the slow rising to abrupt, fast rising of the filament, overlying peripheral magnetic loops display different responses. Two magnetic loops on the elbow of the active region had a slow descending motion followed by an abrupt successive fast contraction, while magnetic loops on the top of the filament were pushed outward, slowly being inflated for a while and then erupting as a moving front. We show that the filament activation and eruption play a dominant role in determining the dynamics of the overlying peripheral coronal magnetic loops.

  1. OPTICAL DISCOVERY OF PROBABLE STELLAR TIDAL DISRUPTION FLARES

    SciTech Connect (OSTI)

    Van Velzen, Sjoert; Farrar, Glennys R. [Center for Cosmology and Particle Physics, New York University, NY 10003 (United States); Gezari, Suvi [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Morrell, Nidia [Carnegie Observatories, Las Campanas Observatory, Casillas 601, La Serena (Chile); Zaritsky, Dennis [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Oestman, Linda [Institut de Fisica d'Altes Energies, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Barcelona) (Spain); Smith, Mathew [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, 7701 (South Africa); Gelfand, Joseph [New York University-Abu Dhabi, Abu Dhabi (United Arab Emirates); Drake, Andrew J., E-mail: s.vanvelzen@astro.ru.nl [Center for Advance Computing Research, California Institute of Technology, Pasadena, CA 91225 (United States)

    2011-11-10

    Using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption of stars by supermassive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified. The TDE flares have optical blackbody temperatures of 2 Multiplication-Sign 10{sup 4} K and observed peak luminosities of M{sub g} = -18.3 and -20.4 ({nu}L{sub {nu}} = 5 Multiplication-Sign 10{sup 42}, 4 Multiplication-Sign 10{sup 43} erg s{sup -1}, in the rest frame); their cooling rates are very low, qualitatively consistent with expectations for tidal disruption flares. The properties of the TDE candidates are examined using (1) SDSS imaging to compare them to other flares observed in the search, (2) UV emission measured by GALEX, and (3) spectra of the hosts and of one of the flares. Our pipeline excludes optically identifiable AGN hosts, and our variability monitoring over nine years provides strong evidence that these are not flares in hidden AGNs. The spectra and color evolution of the flares are unlike any SN observed to date, their strong late-time UV emission is particularly distinctive, and they are nuclear at high resolution arguing against these being first cases of a previously unobserved class of SNe or more extreme examples of known SN types. Taken together, the observed properties are difficult to reconcile with an SN or an AGN-flare explanation, although an entirely new process specific to the inner few hundred parsecs of non-active galaxies cannot be excluded. Based on our observed rate, we infer that hundreds or thousands of TDEs will be present in current and next-generation optical synoptic surveys. Using the approach outlined here, a TDE candidate sample with O(1) purity can be selected using geometric resolution and host and flare color alone, demonstrating that a campaign to create a large sample of TDEs, with immediate and detailed multi-wavelength follow-up, is feasible. A by-product of this work is quantification of the power spectrum of extreme flares in AGNs.

  2. From coronal observations to MHD simulations, the building blocks for 3D models of solar flares

    E-Print Network [OSTI]

    Janvier, Miho; Demoulin, Pascal

    2015-01-01

    Solar flares are energetic events taking place in the Sun's atmosphere, and their effects can greatly impact the environment of the surrounding planets. In particular, eruptive flares, as opposed to confined flares, launch coronal mass ejections into the interplanetary medium, and as such, are one of the main drivers of space weather. After briefly reviewing the main characteristics of solar flares, we summarize the processes that can account for the build up and release of energy during their evolution. In particular, we focus on the development of recent 3D numerical simulations that explain many of the observed flare features. These simulations can also provide predictions of the dynamical evolution of coronal and photospheric magnetic field. Here we present a few observational examples that, together with numerical modelling, point to the underlying physical mechanisms of the eruptions.

  3. Earth Planets Space, , , Flares and the Chromosphere

    E-Print Network [OSTI]

    Hudson, Hugh

    produces in the photospheric magnetic field. Key words: Solar flares, Solar chromosphere, Solar corona understand about solar flares. The reason for this was the recognition, in the 19th and early 20th cen The radiative energy of a solar flare appears mainly in the optical and UV continuum, which form in the lower

  4. OVERVIEW OF SOLAR FLARES The Yohkoh Perspective

    E-Print Network [OSTI]

    California at Berkeley, University of

    Chapter 8 OVERVIEW OF SOLAR FLARES The Yohkoh Perspective Hugh Hudson Space Sciences Laboratory, UC This chapter reviews the physics of solar flares, with special emphasis on the past decade. During this decade, corona 1 #12;2 1. Introduction The physics of solar flares seems too broad a subject to review adequately

  5. Solar Flares STFC Advanced Summer School

    E-Print Network [OSTI]

    California at Berkeley, University of

    Solar Flares STFC Advanced Summer School in Solar Physics H. S. Hudson Space Sciences Laboratory · A solar flare is, strictly speaking, the electromagnetic radiation from a coronal magnetic energy release and CME require a magnetic storage to supply the energy: #12;Glasgow Summerschool 2011 Why is flare

  6. Thermodynamic Spectrum of Solar Flares Based on SDO/EVE Observations: Techniques and First Results

    E-Print Network [OSTI]

    Wang, Yuming; Zhang, Jie; Liu, Kai; Liu, Rui; Shen, Chenglong; Chamberlin, Phillip C

    2015-01-01

    SDO/EVE provide rich information of the thermodynamic processes of solar activities, particularly of solar flares. Here, we develop a method to construct thermodynamic spectrum (TDS) charts based on the EVE spectral lines. Reading from the charts, we are able to easily recognize if there is a late phase following a main phase of a flare, and able to learn the begin, peak and end times of the flare as well as the drift of the temperature, i.e., the cooling rate, of the heated plasma during the flare. Through four M-class flares of different types, we illustrate which thermodynamic information can be revealed from the TDS charts. Further, we investigate the TDS charts of all the flares greater than M5.0, and some interesting results are achieved. First, there are two distinct drift patterns, called Type I and Type II. For Type I flares, the enhanced emission drifts from high to low temperture, whereas for Type II flares, the drift is somewhat reversed, suggesting a more violent and durable heating during Type I...

  7. Plasma motions and non-thermal line broadening in flaring twisted coronal loops

    E-Print Network [OSTI]

    Gordovskyy, Mykola; Browning, Philippa

    2015-01-01

    Observation of coronal EUV spectral lines offers an opportunity to evaluate the thermal structure and flows in flaring atmospheres. This, in turn, can be used to estimate the partitioning between the thermal and kinetic energies released in flares. Our aim is to forward-model large-scale (50-10000 km) velocity distributions in order to interpret non-thermal broadening of different spectral EUV lines observed in flares. The developed models allow us to understand the origin of the observed spectral line shifts and broadening, and link these features to particular physical phenomena in flaring atmospheres. We use ideal MHD to derive unstable twisted magnetic fluxtube configurations in a gravitationally-stratified atmosphere. The evolution of these twisted fluxtubes is followed using resistive MHD, with anomalous resistivity depending on the local density and temperature. The model also takes into account the thermal conduction and radiative losses. The model allows us to evaluate average velocities and velocity...

  8. Scaling laws of solar and stellar flares

    E-Print Network [OSTI]

    Markus J. Aschwanden; Robert A. Stern; Manuel Güdel

    2007-10-12

    In this study we compile for the first time comprehensive data sets of solar and stellar flare parameters, including flare peak temperatures T_p, flare peak volume emission measures EM_p, and flare durations t_f from both solar and stellar data, as well as flare length scales L from solar data. Key results are that both the solar and stellar data are consistent with a common scaling law of EM_p ~ T_p^4.7, but the stellar flares exhibit ~250 times higher emission measures (at the same flare peak temperature). For solar flares we observe also systematic trends for the flare length scale L(T_p) ~ T_p^0.9 and the flare duration t_F(T_p) ~ T_p^0.9 as a function of the flare peak temperature. Using the theoretical RTV scaling law and the fractal volume scaling observed for solar flares, i.e., V(L) ~ L^2.4, we predict a scaling law of EM_p ~ T_p^4.3, which is consistent with observations, and a scaling law for electron densities in flare loops, n_p ~ T_p^2/L ~ T_p^1.1. The RTV-predicted electron densities were also found to be consistent with densities inferred from total emission measures, n_p=(EM_p/q_V*V)^1/2, using volume filling factors of q_V=0.03-0.08 constrained by fractal dimensions measured in solar flares. Our results affect also the determination of radiative and conductive cooling times, thermal energies, and frequency distributions of solar and stellar flare energies.

  9. Detecting Solar Neutrino Flares and Flavors

    E-Print Network [OSTI]

    D. Fargion

    2004-04-16

    Intense solar flares originated in sun spots produce high energy particles (protons, $\\alpha$) well observable by satellites and ground-based detectors. The flare onset produces signals in different energy bands (radio, X, gamma and neutrons). The most powerful solar flares as the ones occurred on 23 February 1956, 29 September 1989 and the more recent on October 28th, and the 2nd, 4th, 13th of November 2003 released in sharp times the largest flare energies (${E}_{FL} \\simeq {10}^{31}\\div {10}^{32} erg). The high energy solar flare protons scatter within the solar corona and they must be source of a prompt neutrino burst through the production of charged pions. Later on, solar flare particles hitting the atmosphere may marginally increase the atmospheric neutrino flux. The prompt solar neutrino flare may be detected in the largest underground $\

  10. HELIOPHYSICS II. ENERGY CONVERSION PROCESSES

    E-Print Network [OSTI]

    Hudson, Hugh

    with the term "solar flare" dominate our thinking about energy conversion from magnetic storage to other formsHELIOPHYSICS II. ENERGY CONVERSION PROCESSES edited by CAROLUS J. SCHRIJVER Lockheed Martin of a solar flare 11 2.3.1 Flare luminosity and mechanical energy 11 2.3.2 The impulsive phase (hard X

  11. Multi-wavelength analysis of high energy electrons in solar flares: a case study of August 20, 2002 flare

    E-Print Network [OSTI]

    J. Kasparova; M. Karlicky; E. P. Kontar; R. A. Schwartz; B. R. Dennis

    2005-08-30

    A multi-wavelength spatial and temporal analysis of solar high energy electrons is conducted using the August 20, 2002 flare of an unusually flat (gamma=1.8) hard X-ray spectrum. The flare is studied using RHESSI, Halpha, radio, TRACE, and MDI observations with advanced methods and techniques never previously applied in the solar flare context. A new method to account for X-ray Compton backscattering in the photosphere (photospheric albedo) has been used to deduce the primary X-ray flare spectra. The mean electron flux distribution has been analysed using both forward fitting and model independent inversion methods of spectral analysis. We show that the contribution of the photospheric albedo to the photon spectrum modifies the calculated mean electron flux distribution, mainly at energies below 100 keV. The positions of the Halpha emission and hard X-ray sources with respect to the current-free extrapolation of the MDI photospheric magnetic field and the characteristics of the radio emission provide evidence of the closed geometry of the magnetic field structure and the flare process in low altitude magnetic loops. In agreement with the predictions of some solar flare models, the hard X-ray sources are located on the external edges of the Halpha emission and show chromospheric plasma heated by the non-thermal electrons. The fast changes of Halpha intensities are located not only inside the hard X-ray sources, as expected if they are the signatures of the chromospheric response to the electron bombardment, but also away from them.

  12. Plasma Turbulence and Stochastic Acceleration in Solar Flares

    E-Print Network [OSTI]

    Vahe Petrosian

    1999-11-18

    Observational aspects of solar flares relevant to the acceleration process of electrons and protons are reviewed and it is shown that most of these observations can be explained by the interaction with flare plasma of a power law energy distribution of electrons (and protons) that are injected at the top of a flaring loop, in the so-called thick target model. Some new observations that do not agree with this model are described and it is shown that these can be explained most naturally if most of the energy released by the reconnection process goes first into the generation of plasma turbulence, which accelerates, scatters and traps the ambient electrons near the top of the loop stochastically. The resultant bremsstrahlung photon spectral and spatial distributions agree with the new observations. This model is also justified by some theoretical arguments. Results from numerical evaluation of the spectra of the accelerated electrons and their bremsstrahlung emission are compared with observations and shown how one can constrain the model parameters describing the flare plasma and the spectrum and the energy density of the turbulence.

  13. RETURN CURRENTS AND ENERGY TRANSPORT IN THE SOLAR FLARING ATMOSPHERE

    SciTech Connect (OSTI)

    Codispoti, Anna; Torre, Gabriele; Piana, Michele; Pinamonti, Nicola [Dipartimento di Matematica, Universita di Genova, via Dodecaneso 35, I-16146 Genova (Italy)

    2013-08-20

    According to the standard Ohmic perspective, the injection of accelerated electrons into the flaring region violates local charge equilibrium and therefore, in response, return currents are driven by an electric field to equilibrate such charge violation. In this framework, the energy loss rate associated with these local currents has an Ohmic nature and significantly shortens the accelerated electron path. In the present paper, we adopt a different viewpoint and, specifically, we study the impact of the background drift velocity on the energy loss rate of accelerated electrons in solar flares. We first utilize the Rutherford cross-section to derive the formula of the energy loss rate when the collisional target has a finite temperature and the background instantaneously and coherently moves up to equilibrate the electron injection. We then use the continuity equation for electrons and imaging spectroscopy data provided by RHESSI to validate this model. We show that this new formula for the energy loss rate provides a better fit of the experimental data with respect to the model based on the effects of standard Ohmic return currents.

  14. Magnetic reconnection configurations and particle acceleration in solar flares

    E-Print Network [OSTI]

    Chen, P. F.

    types of solar flares. Upper panel: two-ribbon flares; Lower panel: compact flares. The color showsMagnetic reconnection configurations and particle acceleration in solar flares P. F. Chen, W. J space under different magnetic configurations. Key words: solar flares, magnetic reconnection, particle

  15. Recent Flare Studies at NJIT Outline of Studies

    E-Print Network [OSTI]

    continuum brightening (white-light flares) Black-light solar flares (BLFs; Henoux et al. 1990): electron flares. - Solar limb in D3, showing a narrow, bright band above the photosphere between 1000 and 2500 km3/28/2014 1 Recent Flare Studies at NJIT Lecture 10 Outline of Studies Black Light Flares Moreton

  16. The Search for >35 MeV Neutrons from the June 3, 2012 Impulsive Flare

    E-Print Network [OSTI]

    Koga, K; Matsumoto, H; Muraki, Y; Okudaira, T Obara O; Shibata, S; Yamamoto, T; Goka, T

    2015-01-01

    We analyzed a highly impulsive solar flare observed on June 3, 2012. In association with this flare, emissions of hard X-rays, high-energy gamma rays, and neutrons were detected by the detectors onboard the FERMI, RHESSI satellites and the International Space Station. We compared those results with the pictures taken by the UV telescope onboard the Solar Dynamics Observatory satellite and found the crossing structure of two magnetic ropes at two positions on the solar surface almost at the same time. High-energy gamma rays were detected by the Fermi Large Area Telescope satellite, implying that the impulsive flare was one of a major source of proton acceleration processes on the solar surface. At the beginning of research, impulsive solar flares were considered to be the main source of particle acceleration processes; our current observations have confirmed this hypothesis.

  17. Solar flare electron acceleration: comparing theories and observations

    E-Print Network [OSTI]

    Arnold O. Benz; Pascal Saint-Hilaire

    2003-08-19

    A popular scenario for electron acceleration in solar flares is transit-time damping of low-frequency MHD waves excited by reconnection and its outflows. The scenario requires several processes in sequence to yield energetic electrons of the observed large number. Until now there was very little evidence for this scenario, as it is even not clear where the flare energy is released. RHESSI measurements of bremsstrahlung by non-thermal flare electrons yield energy estimates as well as the position where the energy is deposited. Thus quantitative measurements can be put into the frame of the global magnetic field configuration as seen in coronal EUV line observations. We present RHESSI observations combined with TRACE data that suggest primary energy inputs mostly into electron acceleration and to a minor fraction into coronal heating and primary motion. The more sensitive and lower energy X-ray observations by RHESSI have found also small events (C class) at the time of the acceleration of electron beams exciting meter wave Type III bursts. However, not all RHESSI flares involve Type III radio emissions. The association of other decimeter radio emissions, such as narrowband spikes and pulsations, with X-rays is summarized in view of electron acceleration

  18. UNIVERSAL BEHAVIOR OF X-RAY FLARES FROM BLACK HOLE SYSTEMS

    SciTech Connect (OSTI)

    Wang, F. Y.; Dai, Z. G.; Yi, S. X.; Xi, S. Q. E-mail: dzg@nju.edu.cn

    2015-01-01

    X-ray flares have been discovered in black hole systems such as gamma-ray bursts, the tidal disruption event Swift J1644+57, the supermassive black hole Sagittarius A* at the center of our Galaxy, and some active galactic nuclei. Occurrences of X-ray flares are always accompanied by relativistic jets. However, it is still unknown whether or not there is a physical analogy among such X-ray flares produced in black hole systems spanning nine orders of magnitude in mass. Here, we report observed data of X-ray flares and show that they have three statistical properties similar to solar flares, including power-law distributions of their energies, durations, and waiting times, which can be explained by a fractal-diffusive, self-organized criticality model. These statistical similarities, together with the fact that solar flares are triggered by a magnetic reconnection process, suggest that all of the X-ray flares are consistent with magnetic reconnection events, implying that their concomitant relativistic jets may be magnetically dominated.

  19. The Ulysses Catalog of Solar Hard X-Ray Flares

    E-Print Network [OSTI]

    Tranquille, C.; Hurley, K.; Hudson, H. S.

    2009-01-01

    Sturrock, P.A. (ed. ) Solar Flares: A Monograph from SkylabSmith E.V.P. : 1963, Solar Flares, Macmillan, New York.Catalog of Solar Hard X-Ray Flares Table 1 (Continued. )

  20. Flare Gas Recovery in Shell Canada Refineries 

    E-Print Network [OSTI]

    Allen, G. D.; Wey, R. E.; Chan, H. H.

    1983-01-01

    six years total operating experience with modern flare gas recovery units. The compression facilities in each utilize a two-stage reciprocating machine, one liquid seal drum per flare stack, and an automated load control strategy. The purpose... these issues. SYSTEM CONFIGURATION A schematic of a typical refinery flare gas recovery facility is shown in Figure I. The facilities include the following pieces of equipment: - compressor suction drum - compressor set - inter-stage knock-out drum...

  1. Solar flares: Preflare Phase SOLAR FLARES are believed to be the result of a sud

    E-Print Network [OSTI]

    Martens, Petrus C.

    build­up and the trigger mechanism is at the heart of understanding the physics of solar flaresSolar flares: Preflare Phase SOLAR FLARES are believed to be the result of a sud­ den conversion of a large amount of FREE MAGNETIC ENERGY, previously stored in the solar CORONA. The release takes place

  2. Evidence of Bulk Acceleration of the GRB X-ray Flare Emission Region

    E-Print Network [OSTI]

    Uhm, Z Lucas

    2015-01-01

    Gamma-ray bursts (GRBs), the most luminous explosions in the universe, invoke relativistic jets beaming towards Earth with the highest velocities for bulk motion in the universe. Some of them are followed by softer, less energetic, X-ray flares, which also move with relativistic velocities towards Earth. Observations and theoretical modeling suggest that X-ray flares share a similar physical mechanism as GRB prompt emission itself. Here we show a clear observational evidence that the X-ray flare emission region is undergoing rapid acceleration as the photons are emitted. The observed X-ray flare light curves and photon index evolution can be interpreted within a simple toy model invoking synchrotron radiation in an accelerating emission region far from the GRB central engine. Such an acceleration process demands an additional energy dissipation source other than kinetic energy, which points towards a significant Poynting-flux in the emission region.

  3. Prediction of Solar Flare Size and Time-to-Flare Using Support Vector Machine Regression

    E-Print Network [OSTI]

    Boucheron, Laura E; McAteer, R T James

    2015-01-01

    We study the prediction of solar flare size and time-to-flare using 38 features describing magnetic complexity of the photospheric magnetic field. This work uses support vector regression to formulate a mapping from the 38-dimensional feature space to a continuous-valued label vector representing flare size or time-to-flare. When we consider flaring regions only, we find an average error in estimating flare size of approximately half a \\emph{geostationary operational environmental satellite} (\\emph{GOES}) class. When we additionally consider non-flaring regions, we find an increased average error of approximately 3/4 a \\emph{GOES} class. We also consider thresholding the regressed flare size for the experiment containing both flaring and non-flaring regions and find a true positive rate of 0.69 and a true negative rate of 0.86 for flare prediction. The results for both of these size regression experiments are consistent across a wide range of predictive time windows, indicating that the magnetic complexity fe...

  4. OBSERVATION OF HEATING BY FLARE-ACCELERATED ELECTRONS IN A SOLAR CORONAL MASS EJECTION

    SciTech Connect (OSTI)

    Glesener, Lindsay; Bain, Hazel M.; Krucker, Säm; Lin, Robert P.

    2013-12-20

    We report a Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observation of flare-accelerated electrons in the core of a coronal mass ejection (CME) and examine their role in heating the CME. Previous CME observations have revealed remarkably high thermal energies that can far surpass the CME's kinetic energy. A joint observation by RHESSI and the Atmospheric Imaging Assembly of a partly occulted flare on 2010 November 3 allows us to test the hypothesis that this excess energy is collisionally deposited by flare-accelerated electrons. Extreme ultraviolet (EUV) images show an ejection forming the CME core and sheath, with isothermal multifilter analysis revealing temperatures of ?11 MK in the core. RHESSI images reveal a large (?100 × 50 arcsec{sup 2}) hard X-ray (HXR) source matching the location, shape, and evolution of the EUV plasma, indicating that the emerging CME is filled with flare-accelerated electrons. The time derivative of the EUV emission matches the HXR light curve (similar to the Neupert effect observed in soft and HXR time profiles), directly linking the CME temperature increase with the nonthermal electron energy loss, while HXR spectroscopy demonstrates that the nonthermal electrons contain enough energy to heat the CME. This is the most direct observation to date of flare-accelerated electrons heating a CME, emphasizing the close relationship of the two in solar eruptive events.

  5. SOLAR FLARE CYCLES , M. D. POPESCU1, 2

    E-Print Network [OSTI]

    SOLAR FLARE CYCLES G. MARI1 , M. D. POPESCU1, 2 1 Astronomical Institute of the Romanian Academy solar flare periodicity intervals. Our analysis includes a statistical investigation of flare occurrence and the strength of solar cycles. For that purpose, we studied not only the number of flares occurring monthly

  6. Effects of Compton scattering on the Gamma Ray Spectra of Solar flares

    E-Print Network [OSTI]

    Jun'ichi Kotoku; Kazuo Makishima; Yukari Matsumoto; Mitsuhiro Kohama; Yukikatsu Terada; Toru Tamagawa

    2007-08-01

    Using fully relativistic GEANT4 simulation tool kit, the transport of energetic electrons generated in solar flares was Monte-Carlo simulated, and resultant bremsstrahlung gamma-ray spectra were calculated. The solar atmosphere was approximated by 10 vertically-stacked zones. The simulation took into account two important physical processes,that the bremsstrahlung photons emitted by precipitating relativistic electrons are strongly forward beamed toward the photosphere, and that the majority of these gamma-rays must be Compton back-scattered by the solar atmosphere in order to reach the observer. Then, the Compton degradation was found to make the observable gamma-ray spectra much softer than is predicted by simple analytic calculations. The gamma-ray signals were found to be enhanced by several conditions, including a broad pitch-angle distribution of the electrons, a near-limb flare longitude, and a significant tilt in the magnetic field lines if the flare longitude is rather small. These results successfully explain several important flare properties observed in the hard X-ray to gamma-ray range, including in particular those obtained with Yohkoh. A comparison of the Yohkoh spectrum from a GOES X3.7 class limb flare on 1998 November 22, with a simulation assuming a broad electron pitch-angle distribution, suggests that gamma-rays from this particular solar flare were a mixture of direct bremsstrahlung photons and their Comptonization.

  7. TIME EVOLUTION OF FLARES IN GRB 130925A: JET PRECESSION IN A BLACK HOLE ACCRETION SYSTEM

    SciTech Connect (OSTI)

    Hou, Shu-Jin; Liu, Tong; Gu, Wei-Min; Sun, Mou-Yuan; Lu, Ju-Fu [Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China); Lin, Da-Bin [Department of Physics and GXU-NAOC Center for Astrophysics and Space Sciences, Guangxi University, Nanning, Guangxi 530004 (China); Wu, Xue-Feng, E-mail: tongliu@xmu.edu.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

    2014-01-20

    GRB 130925A, composed of three gamma-ray emission episodes and a series of orderly flares, has been detected by Swift, Fermi, Konus-Wind, and INTEGRAL. If the third weakest gamma-ray episode can be considered a giant flare, we find that after the second gamma-ray episode observed by INTEGRAL located at about 2000 s, a positive relation exists between the time intervals of the adjacent flares and the time since the episode. We suggest that the second gamma-ray episode and its flares originate from the resumption of the accretion process due to the fragments from the collapsar falling back; such a relation may be related to a hyperaccretion disk around a precessed black hole (BH). We propose that the origin and time evolution of the flares, and the approximately symmetrical temporal structure and spectral evolution of the single flare can be explained well by a jet precession model. In addition, the mass and spin of the BH can be constrained, which indicates a stellar-mass, fast-rotating BH located in the center of GRB 130925A.

  8. Managing Abnormal Operation through Process Integration and Cogeneration Systems 

    E-Print Network [OSTI]

    Kamrava, Serveh

    2014-08-05

    flaring while gaining economic and environmental benefits. It is based on simultaneous design and operational optimization where key flaring sources, causes and consequences of process upsets are identified then included in the energy profile...

  9. Giant AGN Flares and Cosmic Ray Bursts

    E-Print Network [OSTI]

    Glennys R. Farrar; Andrei Gruzinov

    2008-09-15

    We predict a new class of very intense, short-duration AGN flares capable of accelerating the highest energy cosmic rays, resulting from the tidal disruption of a star or from a disk instability. The rate and power of these flares readily explains the observed flux and density statistics of UHECRs. The photon bursts produced by the predicted AGN flares are discussed; they may soon be detectable. Observations are shown to exclude that continuous jets of powerful Active Galactic Nuclei are the sole source of ultrahigh energy cosmic rays; the stringent requirements for Gamma Ray Bursts to be the source are delineated.

  10. The Energetics of a Flaring Solar Active Region, and Observed Flare Statistics

    E-Print Network [OSTI]

    M. S. Wheatland

    2008-02-26

    A stochastic model for the energy of a flaring solar active region is presented, generalising and extending the approach of Wheatland & Glukhov (1998). The probability distribution for the free energy of an active region is described by the solution to a master equation involving deterministic energy input and random jump transitions downwards in energy (solar flares). It is shown how two observable distributions, the flare frequency-energy distribution and the flare waiting-time distribution, may be derived from the steady-state solution to the master equation, for given choices for the energy input and for the rates of flare transitions. An efficient method of numerical solution of the steady-state master equation is presented. Solutions appropriate for flaring, involving a constant rate of energy input and power-law distributed jump transition rates, are numerically investigated. The flare-like solutions exhibit power-law flare frequency-energy distributions below a high energy rollover, set by the largest energy the active region is likely to have. The solutions also exhibit approximately exponential (i.e. Poisson) waiting-time distributions, despite the rate of flaring depending on the free energy of the system.

  11. Extremely Large EUV Late Phase of Solar Flares

    E-Print Network [OSTI]

    Liu, Kai; Zhang, Jie; Cheng, Xin; Liu, Rui; Shen, Chenglong

    2015-01-01

    The second peak in the Fe XVI 33.5 nm line irradiance observed during solar flares by Extreme ultraviolet Variability Experiment (EVE) is known as Extreme UltraViolet (EUV) late phase. Our previous paper (Liu et al. 2013) found that the main emissions in the late phase are originated from large-scale loop arcades that are closely connected to but different from the post flare loops (PFLs), and we also proposed that a long cooling process without additional heating could explain the late phase. In this paper, we define the extremely large late phase because it not only has a bigger peak in the warm 33.5 irradiance profile, but also releases more EUV radiative energy than the main phase. Through detailedly inspecting the EUV images from three point-of-view, it is found that, besides the later phase loop arcades, the more contribution of the extremely large late phase is from a hot structure that fails to erupt. This hot structure is identified as a flux rope, which is quickly energized by the flare reconnection...

  12. The spectral evolution of impulsive solar X-ray flares

    E-Print Network [OSTI]

    Paolo C. Grigis; Arnold O. Benz

    2004-07-20

    The time evolution of the spectral index and the non-thermal flux in 24 impulsive solar hard X-ray flares of GOES class M was studied in RHESSI observations. The high spectral resolution allows for a clean separation of thermal and non-thermal components in the 10-30 keV range, where most of the non-thermal photons are emitted. Spectral index and flux can thus be determined with much better accuracy than before. The spectral soft-hard-soft behavior in rise-peak-decay phases is discovered not only in the general flare development, but even more pronounced in subpeaks. An empirically found power-law dependence between the spectral index and the normalization of the non-thermal flux holds during the rise and decay phases of the emission peaks. It is still present in the combined set of all flares. We find an asymmetry in this dependence between rise and decay phases of the non-thermal emission. There is no delay between flux peak and spectral index minimum. The soft-hard-soft behavior appears to be an intrinsic signature of the elementary electron acceleration process.

  13. The Shape of M Dwarf Flares in Kepler Light Curves

    E-Print Network [OSTI]

    Davenport, James R A

    2015-01-01

    Ultra-precise light curves from Kepler provide the best opportunity to determine rates and statistical properties of stellar flares. From 11 months of data on the active M4 dwarf, GJ 1243, we have built the largest catalog of flares for a single star: over 6100 events. Combining 885 of our most pristine flares, we generated an empirical white-light flare template. This high-fidelity template shows a rapid initial rise, and two distinct exponential cooling phases. This template is useful in constraining flare energies and for improved flare detection in many surveys. Complex, multi-peaked events are more common for higher energy flares in this sample. Using our flare template we characterize the structure of complex events. In this contributed talk, I presented results from our boutique study of GJ 1243, and described an expanded investigation of the structure of complex flares and their connection to solar events.

  14. ON THE DURATION OF BLAZAR SYNCHROTRON FLARES

    SciTech Connect (OSTI)

    Eichmann, B.; Schlickeiser, R.; Rhode, W.

    2012-01-10

    A semi-analytical model is presented that describes the temporal development of a blazar synchrotron flare for the case of a broadband synchrotron power spectrum. We examine three different injection scenarios and present its influence on the synchrotron flare. An accurate approximation of the half-life of a synchrotron flare is analytically computed and we give some illustrative examples of the time evolution of the emergent synchrotron intensity by using a numerical integration method. The synchrotron flare starts at all photon energies right after the injection of ultrarelativistic electrons into the spherical emission volume of radius R and its duration exceeds the light travel time 2R/c in the low energy regime. Furthermore, the flare duration extends by the period of injection of relativistic electrons into the emission knot. However, the energetic and spatial distribution of these injected electrons has no significant influence on the flare duration. We obtain a temporal behavior that agrees most favorably with the observations of PKS 2155-304 on 2006 July 29-30 and it differs considerably from the results that were recently achieved by using a monochromatic approximation of the synchrotron power.

  15. EIT and TRACE responses to flare plasma

    E-Print Network [OSTI]

    D. Tripathi; G. Del Zanna; H. E. Mason; C. Chifor

    2008-02-26

    Aims: To understand the contribution of active region and flare plasmas to the $\\lambda$195 channels of SOHO/EIT (Extreme-ultraviolet Imaging Telescope) and TRACE (Transition Region and Coronal Explorer). Methods: We have analysed an M8 flare simultaneously observed by the Coronal Diagnostic Spectrometer (CDS), EIT, TRACE and RHESSI. We obtained synthetic spectra for the flaring region and an outer region using the differential emission measures (DEM) of emitting plasma based on CDS and RHESSI observations and the CHIANTI atomic database. We then predicted the EIT and TRACE count rates. Results: For the flaring region, both EIT and TRACE images taken through the $\\lambda$195 filter are dominated by Fe ${\\rm XXIV}$ (formed at about 20 MK). However, in the outer region, the emission was primarily due to the Fe${\\rm XII}$, with substantial contributions from other lines. The average count rate for the outer region was within 25% the observed value for EIT, while for TRACE it was a factor of two higher. For the flare region, the predicted count rate was a factor of two (in case of EIT) and a factor of three (in case of TRACE) higher than the actual count rate. Conclusions: During a solar flare, both TRACE and EIT $\\lambda$195 channels are found to be dominated by Fe ${\\rm XXIV}$ emission. Reasonable agreement between predictions and observations is found, however some discrepancies need to be further investigated.

  16. Are there Radio-quiet Solar Flares?

    E-Print Network [OSTI]

    Arnold O. Benz; Roman Brajsa; Jasmina Magdalenic

    2007-01-19

    Some 15% of solar flares having a soft X-ray flux above GOES class C5 are reported to lack coherent radio emission in the 100 - 4000 MHz range (type I - V and decimetric emissions). A detailed study of 29 such events reveals that 22 (76%) of them occurred at a radial distance of more than 800'' from the disk center, indicating that radio waves from the limb may be completely absorbed in some flares. The remaining seven events have statistically significant trends to be weak in GOES class and to have a softer non-thermal X-ray spectrum. All of the non-limb flares that were radio-quiet > 100 MHz were accompanied by metric type III emission below 100 MHz. Out of 201 hard X-ray flares, there was no flare except near the limb (R>800'') without coherent radio emission in the entire meter and decimeter range. We suggest that flares above GOES class C5 generally emit coherent radio waves when observed radially above the source.

  17. ON THE FLARE-INDUCED SEISMICITY IN THE ACTIVE REGION NOAA 10930 AND RELATED ENHANCEMENT OF GLOBAL WAVES IN THE SUN

    SciTech Connect (OSTI)

    Kumar, Brajesh; Venkatakrishnan, P.; Mathur, Savita; Tiwari, Sanjiv Kumar; Garcia, R. A. E-mail: pvk@prl.res.in E-mail: tiwari@mps.mpg.de

    2011-12-10

    A major flare (of class X3.4) occurred on 2006 December 13 in the active region NOAA 10930. This flare event has remained interesting to solar researchers for studies related to particle acceleration during the flare process and the reconfiguration of magnetic fields as well as fine-scale features in the active region. The energy released during flares is also known to induce acoustic oscillations in the Sun. Here, we analyze the line-of-sight velocity patterns in this active region during the X3.4 flare using the Dopplergrams obtained by the Global Oscillation Network Group (GONG) instrument. We have also analyzed the disk-integrated velocity observations of the Sun obtained by the Global Oscillation at Low Frequency (GOLF) instrument on board the Solar and Heliospheric Observatory spacecraft as well as full-disk collapsed velocity signals from GONG observations during this flare to study any possible connection between the flare-related changes seen in the local and global velocity oscillations in the Sun. We apply wavelet transform to the time series of the localized velocity oscillations as well as the global velocity oscillations in the Sun spanning the flare event. The line-of-sight velocity shows significant enhancement in some localized regions of the penumbra of this active region during the flare. The affected region is seen to be away from the locations of the flare ribbons and the hard X-ray footpoints. The sudden enhancement of this velocity seems to be caused by the Lorentz force driven by the 'magnetic jerk' in the localized penumbral region. Application of wavelet analysis to these flare-induced localized seismic signals shows significant enhancement in the high-frequency domain (5 <{nu} < 8 mHz) and a feeble enhancement in the p-mode oscillations (2 <{nu} < 5 mHz) during the flare. On the other hand, the wavelet analysis of GOLF velocity data and the full-disk collapsed GONG velocity data spanning the flare event indicates significant post-flare enhancements in the high-frequency global velocity oscillations in the Sun, as evident from the wavelet power spectrum and the corresponding scale-average variance. The present observations of the flare-induced seismic signals in the active region in context of the driving force are different as compared to previous reports on such cases. We also find indications of a connection between flare-induced localized seismic signals and the excitation of global high-frequency oscillations in the Sun.

  18. Product transfer service chosen over LPG flaring

    SciTech Connect (OSTI)

    Horn, J.; Powers, M.

    1994-07-01

    Seadrift Pipeline Corp. recently decommissioned its Ella Pipeline, an 108-mile, 8-in. line between the King Ranch and a Union Carbide plant at Seadrift, Texas. The pipeline company opted for the product transfer services of pipeline Dehydrators Inc. to evacuate the ethane-rich LPG mixture from the pipeline instead of flaring the LPG or displacing it with nitrogen at operating pressures into another pipeline. The product transfer system of Pipeline Dehydrators incorporates the use of highly specialized portable compressors, heat exchangers and interconnected piping. The product transfer process of evacuating a pipeline is an economically viable method that safely recovers a very high percentage of the product while maintaining product purity. Using positive-displacement compressors, PLD transferred the LPG from the idled 8-in. Ella line into an adjacent 12-in. ethane pipeline that remained in service at approximately 800 psig. Approximately 4.3 million lb of LPG (97% ethane, 2.7% methane and 0.3% propane) were transferred into the ethane pipeline, lowering the pressure on the Ella Pipeline from 800 psig to 65 psig.

  19. Spectral Hardening of Large Solar Flares

    E-Print Network [OSTI]

    Paolo C. Grigis; Arnold O. Benz

    2008-05-01

    RHESSI observations are used to quantitatively study the hard X-ray evolution in 5 large solar flares selected for spectral hardening in the course of the event. The X-ray bremsstrahlung emission from non-thermal electrons is characterized by two spectroscopically distinct phases: impulsive and gradual. The impulsive phase usually consists of several emission spikes following a soft-hard-soft spectral pattern, whereas the gradual stage manifests itself as spectral hardening while the flux slowly decreases. Both the soft-hard-soft (impulsive) phase and the hardening (gradual) phase are well described by piecewise linear dependence of the photon spectral index on the logarithm of the hard X-ray flux. The different linear parts of this relation correspond to different rise and decay phases of emission spikes. The temporal evolution of the spectra is compared with the configuration and motion of the hard X-ray sources in RHESSI images. These observations reveal that the two stages of electron acceleration causing these two different behaviors are closely related in space and time. The transition between the impulsive and gradual phase is found to be smooth and progressive rather than abrupt. This suggests that they arise because of a slow change in a common accelerator rather than being caused by two independent and distinct acceleration processes. We propose that the hardening during the decay phase is caused by continuing particle acceleration with longer trapping in the accelerator before escape.

  20. RADIOACTIVE POSITRON EMITTER PRODUCTION BY ENERGETIC ALPHA PARTICLES IN SOLAR FLARES

    SciTech Connect (OSTI)

    Murphy, R. J. [Code 7650, Naval Research Laboratory, Washington, DC 20375 (United States); Kozlovsky, B. [Tel Aviv University, Tel Aviv (Israel); Share, G. H., E-mail: murphy@ssd5.nrl.navy.mil, E-mail: benz@wise.tau.ac.il, E-mail: share@astro.umd.edu [University of Maryland, College Park, MD 20742 (United States)

    2015-01-01

    Measurements of the 0.511 MeV positron-annihilation line from solar flares are used to explore the flare process in general and ion acceleration in particular. In flares, positrons are produced primarily by the decay of radioactive positron-emitting isotopes resulting from nuclear interactions of flare-accelerated ions with ambient solar material. Kozlovsky et al. provided ion-energy-dependent production cross sections for 67 positron emitters evaluated from their threshold energies (some <1 MeV nucleon{sup –1}) to a GeV nucleon{sup –1}, incorporating them into a computer code for calculating positron-emitter production. Adequate cross-section measurements were available for proton reactions, but not for ?-particle reactions where only crude estimates were possible. Here we re-evaluate the ?-particle cross sections using new measurements and nuclear reaction codes. In typical large gamma-ray line flares, proton reactions dominate positron production, but ?-particle reactions will dominate for steeper accelerated-ion spectra because of their relatively low threshold energies. With the accelerated-{sup 3}He reactions added previously, the code is now reliable for calculating positron production from any distribution of accelerated-ion energies, not just those of typical flares. We have made the code available in the online version of the Journal. We investigate which reactions, projectiles, and ion energies contribute to positron production. We calculate ratios of the annihilation-line fluence to fluences of other gamma-ray lines. Such ratios can be used in interpreting flare data and in determining which nuclear radiation is most sensitive for revealing acceleration of low-energy ions at the Sun.

  1. New waste-heat refrigeration unit cuts flaring, reduces pollution

    SciTech Connect (OSTI)

    Brant, B.; Brueske, S.; Erickson, D.; Papar, R.

    1998-05-18

    Planetec Utility Services Co. Inc. and Energy Concepts Co. (ECC), with the help of the US Department of Energy (DOE), developed and commissioned a unique waste-heat powered LPG recovery plant in August 1997 at the 30,000 b/d Denver refinery, operated by Ultramar Diamond Shamrock (UDS). This new environmentally friendly technology reduces flare emissions and the loss of salable liquid-petroleum products to the fuel-gas system. The waste heat ammonia absorption refrigeration plant (Whaarp) is the first technology of its kind to use low-temperature waste heat (295 F) to achieve sub-zero refrigeration temperatures ({minus}40 F) with the capability of dual temperature loads in a refinery setting. The ammonia absorption refrigeration is applied to the refinery`s fuel-gas makeup streams to condense over 180 b/d of salable liquid hydrocarbon products. The recovered liquid, about 64,000 bbl/year of LPG and gasoline, increases annual refinery profits by nearly $1 million, while substantially reducing air pollution emissions from the refinery`s flare.

  2. Energetic electron propagation in the decay phase of non-thermal flare emission

    SciTech Connect (OSTI)

    Huang, Jing; Yan, Yihua; Tsap, Yuri T.

    2014-06-01

    On the basis of the trap-plus-precipitation model, the peculiarities of non-thermal emission in the decay phase of solar flares have been considered. The calculation formulas for the escape rate of trapped electrons into the loss cone in terms of time profiles of hard X-ray (HXR) and microwave (MW) emission have been obtained. It has been found that the evolution of the spectral indices of non-thermal emission depend on the regimes of the pitch angle diffusion of trapped particles into the loss cone. The properties of non-thermal electrons related to the HXR and MW emission of the solar flare on 2004 November 3 are studied with Nobeyama Radioheliograph, Nobeyama Radio Polarimeters, RHESSI, and Geostationary Operational Environmental Satellite observations. The spectral indices of non-thermal electrons related to MW and HXR emission remained constant or decreased, while the MW escape rate as distinguished from that of the HXRs increased. This may be associated with different diffusion regimes of trapped electrons into the loss cone. New arguments in favor of an important role of the superstrong diffusion for high-energy electrons in flare coronal loops have been obtained.

  3. Statistical analysis of the dynamics of secondary electrons in the flare of a high-voltage beam-type discharge

    SciTech Connect (OSTI)

    Demkin, V. P.; Mel'nichuk, S. V.

    2014-09-15

    In the present work, results of investigations into the dynamics of secondary electrons with helium atoms in the presence of the reverse electric field arising in the flare of a high-voltage pulsed beam-type discharge and leading to degradation of the primary electron beam are presented. The electric field in the discharge of this type at moderate pressures can reach several hundred V/cm and leads to considerable changes in the kinetics of secondary electrons created in the process of propagation of the electron beam generated in the accelerating gap with a grid anode. Moving in the accelerating electric field toward the anode, secondary electrons create the so-called compensating current to the anode. The character of electron motion and the compensating current itself are determined by the ratio of the field strength to the concentration of atoms (E/n). The energy and angular spectra of secondary electrons are calculated by the Monte Carlo method for different ratios E/n of the electric field strength to the helium atom concentration. The motion of secondary electrons with threshold energy is studied for inelastic collisions of helium atoms and differential analysis is carried out of the collisional processes causing energy losses of electrons in helium for different E/n values. The mechanism of creation and accumulation of slow electrons as a result of inelastic collisions of secondary electrons with helium atoms and selective population of metastable states of helium atoms is considered. It is demonstrated that in a wide range of E/n values the motion of secondary electrons in the beam-type discharge flare has the character of drift. At E/n values characteristic for the discharge of the given type, the drift velocity of these electrons is calculated and compared with the available experimental data.

  4. Evaluation of expected solar flare neutrino events in the IceCube observatory

    E-Print Network [OSTI]

    de Wasseige, G; Hanson, K; van Eijndhoven, N; Klein, K -L

    2015-01-01

    Since the end of the eighties and in response to a reported increase in the total neutrino flux in the Homestake experiment in coincidence with a solar flare, solar neutrino detectors have searched for solar flare signals. Neutrinos from the decay of mesons, which are themselves produced in collisions of accelerated protons with the solar atmosphere, would provide a novel window on the underlying physics of the acceleration process. For our studies we focus on the IceCube Neutrino Observatory, a cubic kilometer neutrino detector located at the geographical South Pole. Due to its Supernova data acquisition system and its DeepCore component, dedicated to low energy neutrinos, IceCube may be sensitive to solar flare neutrinos and thus permit either a measurement of the signal or the establishment of more stringent upper limits on the solar flare neutrino flux. We present an approach for a time profile analysis based on a stacking method and an evaluation of a possible solar flare signal in IceCube using the Gean...

  5. Assessing out-of-band flare effects at the wafer level for EUV lithography

    SciTech Connect (OSTI)

    George, Simi; Naulleau, Patrick; Kemp, Charles; Denham, Paul; Rekawa, Senajith

    2010-01-25

    To accurately estimate the flare contribution from the out-of-band (OOB), the integration of a DUV source into the SEMATECH Berkeley 0.3-NA Micro-field Exposure tool is proposed, enabling precisely controlled exposures along with the EUV patterning of resists in vacuum. First measurements evaluating the impact of bandwidth selected exposures with a table-top set-up and subsequent EUV patterning show significant impact on line-edge roughness and process performance. We outline a simulation-based method for computing the effective flare from resist sensitive wavelengths as a function of mask pattern types and sizes. This simulation method is benchmarked against measured OOB flare measurements and the results obtained are in agreement.

  6. Spatial Relationship between Solar Flares and Coronal Mass Ejections

    E-Print Network [OSTI]

    S. Yashiro; G. Michalek; S. Akiyama; N. Gopalswamy; R. A. Howard

    2007-10-16

    We report on the spatial relationship between solar flares and coronal mass ejections (CMEs) observed during 1996-2005 inclusive. We identified 496 flare-CME pairs considering limb flares (distance from central meridian > 45 deg) with soft X-ray flare size > C3 level. The CMEs were detected by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). We investigated the flare positions with respect to the CME span for the events with X-class, M-class, and C-class flares separately. It is found that the most frequent flare site is at the center of the CME span for all the three classes, but that frequency is different for the different classes. Many X-class flares often lie at the center of the associated CME, while C-class flares widely spread to the outside of the CME span. The former is different from previous studies, which concluded that no preferred flare site exists. We compared our result with the previous studies and conclude that the long-term LASCO observation enabled us to obtain the detailed spatial relation between flares and CMEs. Our finding calls for a closer flare-CME relationship and supports eruption models typified by the CSHKP magnetic reconnection model.

  7. Rapid Transition of Uncombed Penumbrae to Faculae during Large Flares

    E-Print Network [OSTI]

    field evolution in solar photosphere plays important roles in building energy and triggering eruption structure associated with major flares. Taking advantage of two near-limb events, we found that in sections: flares -- Sun: magnetic topology -- sunspots #12;­ 2 ­ 1. INTRODUCTION Solar flares have been understood

  8. Version on March 21, 2002 STATISTICAL EVIDENCE FOR SYMPATHETIC FLARES

    E-Print Network [OSTI]

    . Subject headings: Sun: flare - Sun: X-ray - Sun: corona 1 Big Bear Solar Observatory, NJIT, 40386 North as solar flares in different active regions that apparently occur as the common result of activation, which are defined as unrelated solar flares that occur at nearly the same time. However

  9. Probabilistic forecasting of solar flares from vector magnetogram data

    E-Print Network [OSTI]

    Barnes, Graham

    Probabilistic forecasting of solar flares from vector magnetogram data G. Barnes,1 K. D. Leka,1 E to solar flare forecasting, adapted to provide the probability that a measurement belongs to either group, the groups in this case being solar active regions which produced a flare within 24 hours and those

  10. Driving Major Solar Flares and Eruptions: Carolus J. Schrijver

    E-Print Network [OSTI]

    Schrijver, Karel

    Driving Major Solar Flares and Eruptions: A Review Carolus J. Schrijver Lockheed Martin Adv. Techn: emerging flux 1 Introduction We have known of the phenomenon called 'solar flare' ever since the first,000 refereed publications with the words 'flare' and 'Sun' or 'solar' in the abstract. Even the limited focus

  11. THE 22-YEAR SOLAR MAGNETIC CYCLE. II. FLARE ACTIVITY

    E-Print Network [OSTI]

    THE 22-YEAR SOLAR MAGNETIC CYCLE. II. FLARE ACTIVITY G. MARI, M. D. POPESCU, A. C. DONEA, M. MIERLA cycle, a cycle that had an unexpected behaviour. Here we analyze the occurrence of the solar flares predicted of the current 11-year solar cycle. We conclude that it could be determined by a pulse of flare

  12. From GHz to mHz: A Multiwavelength Study of the Acoustically Active 14 August 2004 M7.4 Solar Flare

    E-Print Network [OSTI]

    J. C. Martinez-Oliveros; H. Moradi; D. Besliu-Ionescu; A. -C Donea; P. S. Cally; C. Lindsey

    2007-07-13

    We carried out an electromagnetic acoustic analysis of the solar flare of 14 August 2004 in active region AR10656 from the radio to the hard X-ray spectrum. The flare was a GOES soft X-ray class M7.4 and produced a detectable sun quake, confirming earlier inferences that relatively low-energy flares may be able to generate sun quakes. We introduce the hypothesis that the seismicity of the active region is closely related to the heights of coronal magnetic loops that conduct high-energy particles from the flare. In the case of relatively short magnetic loops, chromospheric evaporation populates the loop interior with ionized gas relatively rapidly, expediting the scattering of remaining trapped high-energy electrons into the magnetic loss cone and their rapid precipitation into the chromosphere. This increases both the intensity and suddenness of the chromospheric heating, satisfying the basic conditions for an acoustic emission that penetrates into the solar interior.

  13. Blazar Flaring Rates Measured with GLAST

    E-Print Network [OSTI]

    C. D. Dermer; B. L. Dingus

    2003-12-22

    We derive the minimum observing time scales to detect a blazar at a given flux level with the LAT on GLAST in the scanning and pointing modes. Based upon Phase 1 observations with EGRET, we predict the GLAST detection rate of blazar flares at different flux levels. With some uncertainty given the poor statistics of bright blazars, we predict that a blazar flare with integral flux >~ 200e-8 ph(> 100 MeV) cm^{-2} s^{-1}, which are the best candidates for Target of Opportunity pointings and extensive temporal and spectral studies, should occur every few days.

  14. Blazar Flaring Rates Measured with GLAST

    E-Print Network [OSTI]

    Dermer, C D

    2004-01-01

    We derive the minimum observing time scales to detect a blazar at a given flux level with the LAT on GLAST in the scanning and pointing modes. Based upon Phase 1 observations with EGRET, we predict the GLAST detection rate of blazar flares at different flux levels. With some uncertainty given the poor statistics of bright blazars, we predict that a blazar flare with integral flux >~ 200e-8 ph(> 100 MeV) cm^{-2} s^{-1}, which are the best candidates for Target of Opportunity pointings and extensive temporal and spectral studies, should occur every few days.

  15. On the detection of neutrinos from solar flares using pion-decay photons to provide a time window template

    E-Print Network [OSTI]

    de Wasseige, G; van Eijndhoven, N; Evenson, P; Klein, K -L

    2015-01-01

    Since the end of the eighties and in response to a reported increase in the total neutrino flux in the Homestake experiment in coincidence with solar flares, solar neutrino detectors have searched for solar flare signals. Even though these detectors have used different solar flare samples and analyses, none of them has been able to confirm the possible signal seen by Homestake. Neutrinos from the decay of mesons, which are themselves produced in collisions of accelerated ions with the solar atmosphere would provide a novel window on the underlying physics of the hadronic acceleration and interaction processes during solar flares. Solar flare neutrino flux measurements would indeed help to constrain current parameters such as the composition of the accelerated flux, the proton/ion spectral index and the high energy cutoff or the magnetic configuration in the interaction region. We describe here a new way to search for these neutrinos by considering a specific solar flare sample and a data driven time window te...

  16. RHESSI AND TRACE OBSERVATIONS OF MULTIPLE FLARE ACTIVITY IN AR 10656 AND ASSOCIATED FILAMENT ERUPTION

    SciTech Connect (OSTI)

    Joshi, Bhuwan; Kushwaha, Upendra; Cho, K.-S.; Veronig, Astrid M.

    2013-07-01

    We present Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Transition Region and Coronal Explorer (TRACE) observations of multiple flare activity that occurred in the NOAA active region 10656 over a period of 2 hr on 2004 August 18. Out of four successive flares, three were class C events, and the final event was a major X1.8 solar eruptive flare. The activities during the pre-eruption phase, i.e., before the X1.8 flare, are characterized by three localized episodes of energy release occurring in the vicinity of a filament that produces intense heating along with non-thermal emission. A few minutes before the eruption, the filament undergoes an activation phase during which it slowly rises with a speed of {approx}12 km s{sup -1}. The filament eruption is accompanied by an X1.8 flare, during which multiple hard X-ray (HXR) bursts are observed up to 100-300 keV energies. We observe a bright and elongated coronal structure simultaneously in E(UV) and 50-100 keV HXR images underneath the expanding filament during the period of HXR bursts, which provides strong evidence for ongoing magnetic reconnection. This phase is accompanied by very high plasma temperatures of {approx}31 MK, followed by the detachment of the prominence from the solar source region. From the location, timing, strength, and spectrum of HXR emission, we conclude that the prominence eruption is driven by the distinct events of magnetic reconnection occurring in the current sheet below the erupting prominence. These multi-wavelength observations also suggest that the localized magnetic reconnections associated with different evolutionary stages of the filament in the pre-eruption phase play an important role in destabilizing the active-region filament through the tether-cutting process, leading to large-scale eruption and X-class flare.

  17. The Relation between Solar Eruption Topologies and Observed Flare Features I: Flare Ribbons

    E-Print Network [OSTI]

    Savcheva, A; McKillop, S; McCauley, P; Hanson, E; Su, Y; Werner, E; DeLuca, E E

    2015-01-01

    In this paper we present a topological magnetic field investigation of seven two-ribbon flares in sigmoidal active regions observed with Hinode, STEREO, and SDO. We first derive the 3D coronal magnetic field structure of all regions using marginally unstable 3D coronal magnetic field models created with the flux rope insertion method. The unstable models have been shown to be a good model of the flaring magnetic field configurations. Regions are selected based on their pre-flare configurations along with the appearance and observational coverage of flare ribbons, and the model is constrained using pre-flare features observed in extreme ultraviolet and X-ray passbands. We perform a topology analysis of the models by computing the squashing factor, Q, in order to determine the locations of prominent quasi-separatrix layers (QSLs). QSLs from these maps are compared to flare ribbons at their full extents. We show that in all cases the straight segments of the two J-shaped ribbons are matched very well by the flux...

  18. MEASUREMENTS OF ABSOLUTE ABUNDANCES IN SOLAR FLARES

    SciTech Connect (OSTI)

    Warren, Harry P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2014-05-01

    We present measurements of elemental abundances in solar flares with the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory. EVE observes both high temperature Fe emission lines (Fe XV-Fe XXIV) and continuum emission from thermal bremsstrahlung that is proportional to the abundance of H. By comparing the relative intensities of line and continuum emission it is possible to determine the enrichment of the flare plasma relative to the composition of the photosphere. This is the first ionization potential or FIP bias (f). Since thermal bremsstrahlung at EUV wavelengths is relatively insensitive to the electron temperature, it is important to account for the distribution of electron temperatures in the emitting plasma. We accomplish this by using the observed spectra to infer the differential emission measure distribution and FIP bias simultaneously. In each of the 21 flares that we analyze we find that the observed composition is close to photospheric. The mean FIP bias in our sample is f = 1.17 ± 0.22. This analysis suggests that the bulk of the plasma evaporated during a flare comes from deep in the chromosphere, below the region where elemental fractionation occurs.

  19. Interplay of Boltzmann equation and continuity equation for accelerated electrons in solar flares

    E-Print Network [OSTI]

    Codispoti, Anna

    2015-01-01

    During solar flares a large amount of electrons are accelerated within the plasma present in the solar atmosphere. Accurate measurements of the motion of these electrons start becoming available from the analysis of hard X-ray imaging-spectroscopy observations. In this paper, we discuss the linearized perturbations of the Boltzmann kinetic equation describing an ensemble of electrons accelerated by the energy release occurring during solar flares. Either in the limit of high energy or at vanishing background temperature such an equation reduces to a continuity equation equipped with an extra force of stochastic nature. This stochastic force is actually described by the well known energy loss rate due to Coulomb collision with ambient particles, but, in order to match the collision kernel in the linearized Boltzmann equation it needs to be treated in a very specific manner. In the second part of the paper the derived continuity equation is solved with some hyperbolic techniques, and the obtained solution is wr...

  20. Properties of Flares-Generated Seismic Waves on the Sun

    E-Print Network [OSTI]

    A. G. Kosovichev

    2005-12-31

    The solar seismic waves excited by solar flares (``sunquakes'') are observed as circular expanding waves on the Sun's surface. The first sunquake was observed for a flare of July 9, 1996, from the Solar and Heliospheric Observatory (SOHO) space mission. However, when the new solar cycle started in 1997, the observations of solar flares from SOHO did not show the seismic waves, similar to the 1996 event, even for large X-class flares during the solar maximum in 2000-2002. The first evidence of the seismic flare signal in this solar cycle was obtained for the 2003 ``Halloween'' events, through acoustic ``egression power'' by Donea and Lindsey. After these several other strong sunquakes have been observed. Here, I present a detailed analysis of the basic properties of the helioseismic waves generated by three solar flares in 2003-2005. For two of these flares, X17 flare of October 28, 2003, and X1.2 flare of January 15, 2005, the helioseismology observations are compared with simultaneous observations of flare X-ray fluxes measured from the RHESSI satellite. These observations show a close association between the flare seismic waves and the hard X-ray source, indicating that high-energy electrons accelerated during the flare impulsive phase produced strong compression waves in the photosphere, causing the sunquake. The results also reveal new physical properties such as strong anisotropy of the seismic waves, the amplitude of which varies significantly with the direction of propagation. The waves travel through surrounding sunspot regions to large distances, up to 120 Mm, without significant decay. These observations open new perspectives for helioseismic diagnostics of flaring active regions on the Sun and for understanding the mechanisms of the energy release and transport in solar flares.

  1. The shock reprocessing model of electron acceleration in impulsive solar flares

    E-Print Network [OSTI]

    Robert Selkowitz; Eric G. Blackman

    2005-09-14

    We propose a new two-stage model for acceleration of electrons in solar flares. In the first stage, electrons are accelerated stochastically in a post-reconnection turbulent downflow. The second stage is the reprocessing of a subset of these electrons as they pass through a weakly compressive fast shock above the apex of the closed flare loop on their way to the chromosphere. We call this the "shock reprocessing" model. The model reproduces the energy dependent arrival time delays observed for both the pulsed and smooth components of impulsive solar flare x-rays with physically reasonable parameters for the downflow region. The model also predicts an emission site above the loop-top, as seen in the Masuda flare. The loop-top source distinguishes the shock reprocessing model from previous models. The model makes testable predictions for the energy dependence of footpoint pulse strengths and the location and spectrum of the loop-top emission, and can account for the observed soft-hard-soft trend in the spectral evolution of footpoint emission. Our model highlights the concept that reconnection is an acceleration environment rather than a single process. Which combination of processes operate may depend on the initial conditions that determine, for example, whether the reconnection downflow is turbulent. The shock reprocessing model comprises one such combination.

  2. THE MECHANISMS FOR THE ONSET AND EXPLOSIVE ERUPTION OF CORONAL MASS EJECTIONS AND ERUPTIVE FLARES

    SciTech Connect (OSTI)

    Karpen, J. T.; Antiochos, S. K.; DeVore, C. R.

    2012-11-20

    We have investigated the onset and acceleration of coronal mass ejections (CMEs) and eruptive flares. To isolate the eruption physics, our study uses the breakout model, which is insensitive to the energy buildup process leading to the eruption. We performed 2.5D simulations with adaptive mesh refinement that achieved the highest overall spatial resolution to date in a CME/eruptive flare simulation. The ultra-high resolution allows us to separate clearly the timing of the various phases of the eruption. Using new computational tools, we have determined the number and evolution of all X- and O-type nulls in the system, thereby tracking both the progress and the products of reconnection throughout the computational domain. Our results show definitively that CME onset is due to the start of fast reconnection at the breakout current sheet. Once this reconnection begins, eruption is inevitable; if this is the only reconnection in the system, however, the eruption will be slow. The explosive CME acceleration is triggered by fast reconnection at the flare current sheet. Our results indicate that the explosive eruption is caused by a resistive instability, not an ideal process. Moreover, both breakout and flare reconnections begin first as a form of weak tearing characterized by slowly evolving plasmoids, but eventually transition to a fast form with well-defined Alfvenic reconnection jets and rapid flux transfer. This transition to fast reconnection is required for both CME onset and explosive acceleration. We discuss the key implications of our results for CME/flare observations and for theories of magnetic reconnection.

  3. An investigation of Fe XV emission lines in solar flare spectra

    E-Print Network [OSTI]

    F P Keenan; K M Aggarwal; D S Bloomfield; A Z Msezane; K G Widing

    2005-12-22

    Previously, large discrepancies have been found between theory and observation for Fe XV emission line ratios in solar flare spectra covering the 224-327 A wavelength range, obtained by the Naval Research Laboratory's S082A instrument on board Skylab. These discrepancies have been attributed to either errors in the adopted atomic data or the presence of additional atomic processes not included in the modelling, such as fluorescence. However our analysis of these plus other S082A flare observations (the latter containing Fe XV transitions between 321-482 A), performed using the most recent Fe XV atomic physics calculations in conjunction with a CHIANTI synthetic flare spectrum, indicate that blending of the lines is primarily responsible for the discrepancies. As a result, most Fe XV lines cannot be employed as electron density diagnostics for solar flares, at least at the spectral resolution of S082A and similar instruments (i.e. ~ 0.1 A). An exception is the intensity ratio I(321.8 A)/I(327.0 A), which appears to provide good estimates of the electron density at this spectral resolution.

  4. Effect of radioactivity decrease. Is there a link with solar flares?

    E-Print Network [OSTI]

    A. G. Parkhomov

    2010-05-15

    Results obtained with multichannel installation created for long-term studies of various processes, are collated with the data published by J.H. Jenkins and E.Fischbach, who found a decrease of 54Mn radioactivity near the time of series of solar flares between 5 and 17 December 2006. Analysis of the data from our installation in December 2006 has not revealed any deviations from the usual behaviour of the count rates for 90Sr-90Y, 60Co and 239Pu sources. The same can be said of the data collected during the period of highly powerful solar flares between 19 October and 4 November 2003. Apparent drops in the count rate were detected between 10 and 12 May 2002 while registering the activity of 60Co and on 19 and 20 June 2004 for 90Sr-90Y source. Around the time of these events, no observations of large solar flares were reported. Thus, proposed link between the drop in the rates of radioactive decay and appearance of solar flares could not be confirmed. From obtained outcomes follows, that the radioactivity drop effect, if it really exists, is rather rare, and that the reason calling this effect unequally influences various radioactive sources.

  5. Relations between concurrent hard X-ray sources in solar flares

    E-Print Network [OSTI]

    Marina Battaglia; Arnold O. Benz

    2006-06-14

    Context: Solar flares release a large fraction of their energy into non-thermal electrons, but it is not clear where and how. Bremsstrahlung X-rays are observed from the corona and chromosphere. Aims: We aim to characterize the acceleration process by the coronal source and its leakage toward the footpoints in the chromosphere. The relations between the sources reflect the geometry and constrict the configuration of the flare. Methods: We studied solar flares of GOES class larger than M1 with three or more hard X-ray sources observed simultaneously in the course of the flare. The events were observed with the X-ray satellite RHESSI from February 2002 until July 2005. We used imaging spectroscopy methods to determine the spectral evolution of each source in each event. The images of all of the five events show two sources visible only at high energies (footpoints) and one source only visible at low energies (coronal or looptop source, in two cases situated over the limb). Results: We find soft-hard-soft behavior in both, coronal source and footpoints. The coronal source is nearly always softer than the footpoints. The footpoint spectra differ significantly only in one event out of five. Conclusions: The observations are consistent with acceleration in the coronal source and an intricate connection between the corona and chromosphere.

  6. TIDAL DISRUPTION FLARES: THE ACCRETION DISK PHASE

    SciTech Connect (OSTI)

    Montesinos Armijo, Matias; De Freitas Pacheco, Jose A. [Observatoire de la Cote d'Azur, Laboratoire Cassiopee, Universite de Nice Sophia-Antipolis Bd de l'Observatoire, BP 4229, 06304 Nice Cedex 4 (France)

    2011-08-01

    The evolution of an accretion disk, formed as a consequence of the disruption of a star by a black hole, is followed by solving numerically hydrodynamic equations. The present investigation aims to study the dependence of resulting light curves on dynamical and physical properties of such a transient disk during its existence. One of the main results derived from our simulations is that blackbody fits of X-ray data tend to overestimate the true mean disk temperature. In fact, the temperature derived from blackbody fits should be identified with the color X-ray temperature rather than the average value derived from the true temperature distribution along the disk. The time interval between the beginning of the circularization of the bound debris and the beginning of the accretion process by the black hole is determined by the viscous (or accretion) timescale, which also fixes the rising part of the resulting light curve. The luminosity peak coincides with the beginning of matter accretion by the black hole and the late evolution of the light curve depends on the evolution of the debris fallback rate. Peak bolometric luminosities are in the range 10{sup 45}-10{sup 46} erg s{sup -1}, whereas peak luminosities in soft X-rays (0.2-2.0 keV) are typically one order of magnitude lower. The typical timescale derived from our preferred models for the flare luminosity to decay by two orders of magnitude is about 3-4 yr. Predicted soft X-ray light curves reproduce quite well data on galaxies in which a variable X-ray emission possibly related to a tidal event was detected. In the cases of NGC 3599 and IC 3599, data are reproduced well by models defined by a black hole with mass {approx}10{sup 7} M{sub sun} and a disrupted star of about 1 solar mass. The X-ray variation observed in XMMSL1 is consistent with a model defined by a black hole with mass {approx}3 x 10{sup 6} M{sub sun} and a disrupted star of 1 solar mass, while that observed in the galaxy situated in the cluster A1689 is consistent with a model including a black hole of {approx}10{sup 7} M{sub sun} and a disrupted star of {approx}0.5 M{sub sun}.

  7. Smokeless Control of Flare Steam Flow Rate 

    E-Print Network [OSTI]

    Agar, J.; Balls, B. W.

    1979-01-01

    inside the glass. The instrument has a vibrating spool accu rately machined from a material resistant to wet H2S, The patented flow path through the transducer (Figure 8) inhibits moisture and dirt from contaminating the spool and enables installation..., also the inclusion of average values for ZG and ZA' REFERENCES 1. API Publication 931, Chapter 15, "Flares", Manual on Disposal of Refinery Wastes, Volume on Atmospheric Emissions, 1977 American Petroleum Institute, Refinery Department, 2120 L...

  8. Super-hot (T > 30 MK) Thermal Plasma in Solar Flares

    E-Print Network [OSTI]

    Caspi, Amir

    2010-01-01

    R. , et al. 1980, in Solar Flares: A Monograph from SKYLABR. , et al. 1980, in Solar Flares: A Monograph from SKYLAB1988, The Physics of Solar Flares (Cambridge, UK: Cambridge

  9. Faint Coronal Hard X-rays From Accelerated Electrons in Solar Flares

    E-Print Network [OSTI]

    Glesener, Lindsay Erin

    2012-01-01

    also be applicable to solar flares. Figure is from Lin (High-Energy Aspects of Solar Flares, (Space Science Reviews2002 July 23 class X4.8 solar flare, showing thermal (red)

  10. Modelling repeatedly flaring delta-sunspots

    E-Print Network [OSTI]

    Chatterjee, Piyali; Carlsson, Mats

    2016-01-01

    Active regions (AR) appearing on the surface of the Sun are classified into $\\alpha$, $\\beta$, $\\gamma$, and $\\delta$ by the rules of the Mount Wilson Observatory, California on the basis of their topological complexity. Amongst these, the $\\delta$-sunspots are known to be super-active and produce the most X-ray flares. Here, we present results from a simulation of the Sun by mimicking the upper layers and the corona, but starting at a more primitive stage than any earlier treatment. We find that this initial state consisting of only a thin sub-photospheric magnetic sheet breaks into multiple flux-tubes which evolve into a colliding-merging system of spots of opposite polarity upon surface emergence, similar to those often seen on the Sun. The simulation goes on to produce many exotic $\\delta$-sunspot associated phenomena: repeated flaring in the range of typical solar flare energy release and ejective helical flux ropes with embedded cool-dense plasma filaments resembling solar coronal mass ejections.

  11. Massively Parallel Simulations of Solar Flares and Plasma Turbulence

    E-Print Network [OSTI]

    Grauer, Rainer

    in space- and astrophysical plasmasystems include solar flares and hydro- or magnetohydrodynamic turbulence a pure MPI parallelization, which, however requires a careful optimization of the multi

  12. An Experiment to Locate the Site of TeV Flaring in M87

    SciTech Connect (OSTI)

    Harris, D.E.; /Harvard-Smithsonian Ctr. Astrophys.; Massaro, F.; /Harvard-Smithsonian Ctr. Astrophys. /KIPAC, Menlo Park /SLAC; Cheung, C.C.; /Natl. Acad. Sci. /Naval Research Lab, Wash., D.C.; Horns, D.; Raue, M.; /Hamburg U.; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.; Wagner, S.; /Heidelberg Observ.; Colin, P.; /Munich, Max Planck Inst.; Mazin, D.; /Barcelona, IFAE; Wagner, R.; /Munich, Max Planck Inst.; Beilicke, M.; /McDonnell Ctr. Space Sci.; LeBohec, S.; Hui, M.; /Utah U.; Mukherjee, R.; /Barnard Coll.

    2012-05-18

    We describe a Chandra X-ray target-of-opportunity project designed to isolate the site of TeV flaring in the radio galaxy M87. To date, we have triggered the Chandra observations only once (2010 April) and by the time of the first of our nine observations, the TeV flare had ended. However, we found that the X-ray intensity of the unresolved nucleus was at an elevated level for our first observation. Of the more than 60 Chandra observations we have made of the M87 jet covering nine years, the nucleus was measured at a comparably high level only three times. Two of these occasions can be associated with TeV flaring, and at the time of the third event, there were no TeV monitoring activities. From the rapidity of the intensity drop of the nucleus, we infer that the size of the emitting region is of order a few light days x the unknown beaming factor; comparable to the same sort of estimate for the TeV emitting region. We also find evidence of spectral evolution in the X-ray band which seems consistent with radiative losses affecting the non-thermal population of the emitting electrons within the unresolved nucleus.

  13. MAGNETAR GIANT FLARES AND THEIR PRECURSORS-FLUX ROPE ERUPTIONS WITH CURRENT SHEETS

    SciTech Connect (OSTI)

    Yu Cong

    2013-07-10

    We propose a catastrophic magnetospheric model for magnetar precursors and their successive giant flares. Axisymmetric models of the magnetosphere, which contain both a helically twisted flux rope and a current sheet, are established based on force-free field configurations. In this model, the helically twisted flux rope would lose its equilibrium and erupt abruptly in response to the slow and quasi-static variations at the ultra-strongly magnetized neutron star's surface. In a previous model without current sheets, only one critical point exists in the flux rope equilibrium curve. New features show up in the equilibrium curves for the flux rope when current sheets appear in the magnetosphere. The causal connection between the precursor and the giant flare, as well as the temporary re-entry of the quiescent state between the precursor and the giant flare, can be naturally explained. Magnetic energy would be released during the catastrophic state transitions. The detailed energetics of the model are also discussed. The current sheet created by the catastrophic loss of equilibrium of the flux rope provides an ideal place for magnetic reconnection. We point out the importance of magnetic reconnection for further enhancement of the energy release during eruptions.

  14. Microwave Signature of Relativistic Positrons in Solar Flares

    E-Print Network [OSTI]

    Fleishman, Gregory; Meshalkina, Nataliia

    2013-01-01

    Relativistic antiparticles can be created in high-energy nuclear interactions; thus, detection of antiparticles in an astrophysical source can tell us something remarkable about the underlying high-energy processes and nuclear interactions. However, once created, the antiparticles remain a minor fraction of their conjugant normal particles, so the detection of the antiparticles represents a big science challenge. To address this challenge we employ imaging and polarimetry of microwave radiation produced as the positrons gyrate in the ambient magnetic field. The key property of the radiation used in this method is that the oppositely charged particles, electrons and positrons, produce radiation with opposite helicity, easily distinguishable by currently operating radio facilities. Analysis of available spatially resolved microwave data augmented by independent magnetic field measurements allows us to remotely detect the relativistic positron component in several solar flares.

  15. Property Loss / Damage Report Damage Loss Details

    E-Print Network [OSTI]

    Ponce, V. Miguel

    Property Loss / Damage Report Damage Loss Details Date & Time of Damage / Loss: Type of damage / loss: Location - specific address / room: Project / Grant associated with damage / loss - grant Police: When was damage / loss first discovered - BY WHOM: Pictures available or attached? Was personal

  16. PRODUCTION OF {sup 9}Be THROUGH THE {alpha}-FUSION REACTION OF METAL-POOR COSMIC RAYS AND STELLAR FLARES

    SciTech Connect (OSTI)

    Kusakabe, Motohiko; Kawasaki, Masahiro E-mail: kawasaki@icrr.u-tokyo.ac.jp

    2013-04-10

    Spectroscopic observations of metal-poor stars have indicated possible {sup 6}Li abundances that are much larger than the primordial abundance predicted in the standard big bang nucleosynthesis model. Possible mechanisms of {sup 6}Li production in metal-poor stars include pregalactic and cosmological cosmic-ray (CR) nucleosynthesis and nucleosynthesis by flare-accelerated nuclides. We study {sup 9}Be production via two-step {alpha}-fusion reactions of CR or flare-accelerated {sup 3,4}He through {sup 6}He and {sup 6,7}Li, in pregalactic structure, intergalactic medium, and stellar surfaces. We solve transfer equations of CR or flare particles and calculate nuclear yields of {sup 6}He, {sup 6,7}Li, and {sup 9}Be taking account of probabilities of processing {sup 6}He and {sup 6,7}Li into {sup 9}Be via fusions with {alpha} particles. Yield ratios, i.e., {sup 9}Be/{sup 6}Li, are then calculated for the CR and flare nucleosynthesis models. We suggest that the future observations of {sup 9}Be in metal-poor stars may find enhanced abundances originating from metal-poor CR or flare activities.

  17. IMPLICATIONS OF MASS AND ENERGY LOSS DUE TO CORONAL MASS EJECTIONS ON MAGNETICALLY ACTIVE STARS

    SciTech Connect (OSTI)

    Drake, Jeremy J.; Cohen, Ofer; Yashiro, Seiji; Gopalswamy, Nat

    2013-02-20

    Analysis of a database of solar coronal mass ejections (CMEs) and associated flares over the period 1996-2007 finds well-behaved power-law relationships between the 1-8 A flare X-ray fluence and CME mass and kinetic energy. We extrapolate these relationships to lower and higher flare energies to estimate the mass and energy loss due to CMEs from stellar coronae, assuming that the observed X-ray emission of the latter is dominated by flares with a frequency as a function of energy dn/dE = kE {sup -{alpha}}. For solar-like stars at saturated levels of X-ray activity, the implied losses depend fairly weakly on the assumed value of {alpha} and are very large: M-dot {approx}5 Multiplication-Sign 10{sup -10} M{sub sun} yr{sup -1} and E-dot {approx}0.1 L{sub sun}. In order to avoid such large energy requirements, either the relationships between CME mass and speed and flare energy must flatten for X-ray fluence {approx}> 10{sup 31} erg, or the flare-CME association must drop significantly below 1 for more energetic events. If active coronae are dominated by flares, then the total coronal energy budget is likely to be up to an order of magnitude larger than the canonical 10{sup -3} L {sub bol} X-ray saturation threshold. This raises the question of what is the maximum energy a magnetic dynamo can extract from a star? For an energy budget of 1% of L {sub bol}, the CME mass loss rate is about 5 Multiplication-Sign 10{sup -11} M {sub Sun} yr{sup -1}.

  18. Manifestations of energetic electrons with anisotropic distributions in solar flares

    E-Print Network [OSTI]

    observations of hard X-ray (HXR) and microwave (MW) emissions in foot- points of solar flares are often closelyManifestations of energetic electrons with anisotropic distributions in solar flares II. Gyrosynchrotron microwave emission Alexey A. Kuznetsov1,2 & Valentina V. Zharkova3 ABSTRACT We investigate

  19. Blazar Alerts with the HAWC Online Flare Monitor

    E-Print Network [OSTI]

    Weisgarber, Thomas

    2015-01-01

    The High Altitude Water Cherenkov (HAWC) Observatory monitors the gamma-ray sky in the 100 GeV to 100 TeV energy range with > 95% uptime and unprecedented sensitivity for a survey instrument. The HAWC Collaboration has implemented an online flare monitor that detects episodes of rapid flaring activity from extragalactic very high energy (VHE) sources in the declination band from -26 to 64 degrees. This allows timely alerts to be sent to multiwavelength instruments without human intervention. The preliminary configuration of the online flare monitor achieves sensitivity to flares of at least 1 hour duration that attain an average flux of 10 times that of the Crab Nebula. While flares of this magnitude are not common, several flares reaching the level of 10 Crab have been observed in the VHE band within the past decade. With its survey capabilities and high duty cycle, HAWC will expand the observational data set on these particularly extreme flares. We characterize the sensitivity of the online flare monitor an...

  20. Initial test of a Bayesian approach to solar flare prediction

    E-Print Network [OSTI]

    M. S. Wheatland

    2004-11-14

    A test of a new Bayesian approach to solar flare prediction (Wheatland 2004a) is presented. The approach uses the past history of flaring together with phenomenological rules of flare statistics to make a prediction for the probability of occurrence of a large flare within an interval of time, or to refine an initial prediction (which may incorporate other information). The test of the method is based on data from the Geostationary Observational Environmental Satellites (GOES), and involves whole-Sun prediction of soft X-ray flares for 1976-2003. The results show that the method somewhat over-predicts the probability of all events above a moderate size, but performs well in predicting large events.

  1. Design Enhancements To Improve Flare Efficiency 

    E-Print Network [OSTI]

    Dooley, K. A.; McLeod, G. M.; Lorenz, M. D.

    1997-01-01

    and purge gases. It was configured as a two-stage system with each stage consisting of multiple burners. The original burners were of a fin plate design. The flare system was designed to operate at low pressure due to venting constraints imposed... was reconfigured to accommodate the lower heat content via the addition of an alternate first stage. The new stage was comprised of three new burners designed for lower flowrates and for gases with lower heating values than the original fin-plate burners...

  2. Summarizing FLARE assay images in colon carcinogenesis 

    E-Print Network [OSTI]

    Leyk Williams, Malgorzata

    2006-04-12

    times the distance between the moments of the head and tail DNA distributions. Symmetry of the head was assumed, and hence the tail area could be identi ed. Another measure used in comet analysis is the relative tail moment (RTM) (Riso et al. 1999... of damage was then computed by the program for each comet. The standard output from FLARE analysis is the relative tail moment (RTM) (Hellman et al. 1995, Morris et al. 1999, Riso et al. 1999), de ned as RTM = 100*(tail moment)/(tail moment + head moment...

  3. Seismic Fragility Analysis and Loss Estimation for Concrete Structures 

    E-Print Network [OSTI]

    Bai, Jong Wha

    2012-02-14

    seismic vulnerability of concrete structures and effective in quantifying the uncertainties in the loss estimation process....

  4. The Flare-ona of EK Draconis

    E-Print Network [OSTI]

    Ayres, Thomas R

    2015-01-01

    EK Draconis (HD 129333: G1.5 V) is a well-known young (50 Myr) solar analog. In 2012, Hubble Space Telescope returned to EK Dra to follow up a far-ultraviolet (FUV) SNAPshot visit by Cosmic Origins Spectrograph (COS) two years earlier. The brief SNAP pointing had found surprisingly redshifted, impulsively variable subcoronal "hot-line" emission of Si IV 140 nm (T~ 80,000 K). Serendipitously, the 2012 follow-on program witnessed one of the largest FUV flares ever recorded on a sunlike star, which again displayed strong redshifts (downflows) of 30-40 km/s, even after compensating for small systematics in the COS velocity scales, uncovered through a cross-calibration by Space Telescope Imaging Spectrograph (STIS). The (now reduced, but still substantial) ~10 km/s hot-line redshifts outside the flaring interval did not vary with rotational phase, so cannot be caused by "Doppler Imaging" (bright surface patches near a receding limb). Density diagnostic O IV] 140 nm multiplet line ratios of EK Dra suggest log(Ne)~ ...

  5. The study of solar flares with the extended cellular automaton (XCA) model

    E-Print Network [OSTI]

    Anastasiadis, Anastasios

    ) at a temporal snap­shot during a flare. explain the power­law frequency distributions of the solar flareThe study of solar flares with the extended cellular automaton (X­CA) model H. Isliker 1 , A of cellular automaton (CA) model, the extended CA (X­CA), for the study of solar flares. The X­CA model

  6. SMALL AND LARGE-SCALE MAGNETIC FIELDS INVOLVED WITH SOLAR FLARES

    E-Print Network [OSTI]

    ABSTRACT SMALL AND LARGE-SCALE MAGNETIC FIELDS INVOLVED WITH SOLAR FLARES by Chang Liu Solar flares of an EUV sigmoid. #12;SMALL AND LARGE-SCALE MAGNETIC FIELDS INVOLVED WITH SOLAR FLARES by Chang Liu RESERVED #12;APPROVAL PAGE SMALL AND LARGE-SCALE MAGNETIC FIELDS INVOLVED WITH SOLAR FLARES Chang Liu Dr

  7. Solar Flares and the Chromosphere A white paper for the Decadal Survey*

    E-Print Network [OSTI]

    California at Berkeley, University of

    Solar Flares and the Chromosphere A white paper for the Decadal Survey* L. Fletcher, R. Turkmani, H acceleration (De Pontieu et al. 2007). The need for chromospheric observations of flares: The solar flare of radiation in a solar flare (Canfield et al 1986, Neidig 1989, Woods et al. 2004). In other words, solar

  8. Earth Planets Space, 00, 000--000, 2000 Solar Flare Mechanism Based on Magnetic Arcade

    E-Print Network [OSTI]

    Earth Planets Space, 00, 000--000, 2000 Solar Flare Mechanism Based on Magnetic Arcade Reconnection of solar flares based on re­ sistive reconnection of magnetic field subject to continuous increase flares. 1. INTRODUCTION Solar flares are intense, abrupt release of energy occurring usually

  9. X-ray and EUV Observations of GOES C8 Solar Flare

    E-Print Network [OSTI]

    Wolfe, Patrick J.

    X-ray and EUV Observations of GOES C8 Solar Flare Events Kathy Reeves1, Trevor Bowen1,2, Paola;Solar Flares Tuesday, February 19, 2013 #12;Solar Flares Tuesday, February 19, 2013 #12;Solar Dynamics Veronig et al, A&A, 2002 Tuesday, February 19, 2013 #12;Flare Timing GOESflux(Wm-2) Rise Decay Tuesday

  10. GAMMA-RAY POLARIMETRY OF TWO X-CLASS SOLAR FLARES Steven E. Boggs,1

    E-Print Network [OSTI]

    California at Berkeley, University of

    GAMMA-RAY POLARIMETRY OF TWO X-CLASS SOLAR FLARES Steven E. Boggs,1 W. Coburn, and E. Kalemci Space 2005 May 29; accepted 2005 October 18 ABSTRACT We have performed the first polarimetry of solar flare Energy Solar Spectroscopic Imager (RHESSI) for two large flares: the GOES X4.8-class solar flare of 2002

  11. The Effects of Solar Flares on Planetary Ionospheres PAUL WITHERS1

    E-Print Network [OSTI]

    Withers, Paul

    The Effects of Solar Flares on Planetary Ionospheres PAUL WITHERS1 and MICHAEL MENDILLO1 1 Center 353 1531) During solar flares, the Sun's X-ray irradiance increases dramatically, often within a few during solar flares. Similar increases in plasma densities during solar flares have been observed

  12. Distinguishing Solar Flare Types by Differences in Reconnection Regions

    E-Print Network [OSTI]

    Eric G. Blackman

    1997-04-24

    Observations show that magnetic reconnection and its slow shocks occur in solar flares. The basic magnetic structures are similar for long duration event (LDE) flares and faster compact impulsive (CI) flares, but the former require less non-thermal electrons than the latter. Slow shocks can produce the required non-thermal electron spectrum for CI flares by Fermi acceleration if electrons are injected with large enough energies to resonate with scattering waves. The dissipation region may provide the injection electrons, so the overall number of non-thermal electrons reaching the footpoints would depend on the size of the dissipation region and its distance from the chromosphere. In this picture, the LDE flares have converging inflows toward a dissipation region that spans a smaller overall length fraction than for CI flares. Bright loop-top X-ray spots in some CI flares can be attributed to particle trapping at fast shocks in the downstream flow, the presence of which is determined by the angle of the inflow field and velocity to the slow shocks.

  13. OBSERVATIONS OF THERMAL FLARE PLASMA WITH THE EUV VARIABILITY EXPERIMENT

    SciTech Connect (OSTI)

    Warren, Harry P.; Doschek, George A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Mariska, John T. [School of Physics, Astronomy, and Computational Sciences, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)

    2013-06-20

    One of the defining characteristics of a solar flare is the impulsive formation of very high temperature plasma. The properties of the thermal emission are not well understood, however, and the analysis of solar flare observations is often predicated on the assumption that the flare plasma is isothermal. The EUV Variability Experiment (EVE) on the Solar Dynamics Observatory provides spectrally resolved observations of emission lines that span a wide range of temperatures (e.g., Fe XV-Fe XXIV) and allow for thermal flare plasma to be studied in detail. In this paper we describe a method for computing the differential emission measure distribution in a flare using EVE observations and apply it to several representative events. We find that in all phases of the flare the differential emission measure distribution is broad. Comparisons of EVE spectra with calculations based on parameters derived from the Geostationary Operational Environmental Satellites soft X-ray fluxes indicate that the isothermal approximation is generally a poor representation of the thermal structure of a flare.

  14. CONSTRAINING SOLAR FLARE DIFFERENTIAL EMISSION MEASURES WITH EVE AND RHESSI

    SciTech Connect (OSTI)

    Caspi, Amir [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States); McTiernan, James M. [Space Sciences Laboratory University of California, Berkeley, CA 94720 (United States); Warren, Harry P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2014-06-20

    Deriving a well-constrained differential emission measure (DEM) distribution for solar flares has historically been difficult, primarily because no single instrument is sensitive to the full range of coronal temperatures observed in flares, from ?2 to ?50 MK. We present a new technique, combining extreme ultraviolet (EUV) spectra from the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory with X-ray spectra from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), to derive, for the first time, a self-consistent, well-constrained DEM for jointly observed solar flares. EVE is sensitive to ?2-25 MK thermal plasma emission, and RHESSI to ?10 MK; together, the two instruments cover the full range of flare coronal plasma temperatures. We have validated the new technique on artificial test data, and apply it to two X-class flares from solar cycle 24 to determine the flare DEM and its temporal evolution; the constraints on the thermal emission derived from the EVE data also constrain the low energy cutoff of the non-thermal electrons, a crucial parameter for flare energetics. The DEM analysis can also be used to predict the soft X-ray flux in the poorly observed ?0.4-5 nm range, with important applications for geospace science.

  15. Distinguishing Solar Flare Types by Differences in Reconnection Regions

    E-Print Network [OSTI]

    Blackman, E G

    1997-01-01

    Observations show that magnetic reconnection and its slow shocks occur in solar flares. The basic magnetic structures are similar for long duration event (LDE) flares and faster compact impulsive (CI) flares, but the former require less non-thermal electrons than the latter. Slow shocks can produce the required non-thermal electron spectrum for CI flares by Fermi acceleration if electrons are injected with large enough energies to resonate with scattering waves. The dissipation region may provide the injection electrons, so the overall number of non-thermal electrons reaching the footpoints would depend on the size of the dissipation region and its distance from the chromosphere. In this picture, the LDE flares have converging inflows toward a dissipation region that spans a smaller overall length fraction than for CI flares. Bright loop-top X-ray spots in some CI flares can be attributed to particle trapping at fast shocks in the downstream flow, the presence of which is determined by the angle of the inflow...

  16. Discovering Tau and Muon Solar Neutrino Flares above backgrounds

    E-Print Network [OSTI]

    D. Fargion; F. Moscato

    2004-07-11

    Solar neutrino flares astronomy is at the edge of its discover. High energy flare particles (protons, alpha) whose self scattering within the solar corona is source of a rich prompt charged pions are also source of sharp solar neutrino "burst" (at tens-hundred MeV) produced by their pion-muon primary decay in flight. This brief (minute) solar neutrino "burst" at largest peak overcome by four-five order of magnitude the steady atmospheric neutrino noise at the Earth. Later on, solar flare particles hitting the terrestrial atmosphere may marginally increase the atmospheric neutrino flux without relevant consequences. Largest prompt "burst" solar neutrino flare may be detected in present or better in future largest neutrino underground neutrino detectors. Our estimate for the recent and exceptional October - November 2003 solar flares gives a number of events above or just near unity for Super-Kamiokande. The neutrino spectra may reflect in a subtle way the neutrino flavour mixing in flight. A surprising tau appearance may even occur for a hard ({E}_{nu}_{mu}--> {E}_{nu}_{tau} > 4 GeV) flare spectra. A comparison of the solar neutrino flare (at their birth place on Sun and after oscillation on the arrival on the Earth) with other neutrino foreground is here described and it offer an independent road map to disentangle the neutrino flavour puzzles and its secret flavour mixing angles .

  17. Solar Flare Measurements with STIX and MiSolFA

    E-Print Network [OSTI]

    Casadei, Diego

    2014-01-01

    Solar flares are the most powerful events in the solar system and the brightest sources of X-rays, often associated with emission of particles reaching the Earth and causing geomagnetic storms, giving problems to communication, airplanes and even black-outs. X-rays emitted by accelerated electrons are the most direct probe of solar flare phenomena. The Micro Solar-Flare Apparatus (MiSolFA) is a proposed compact X-ray detector which will address the two biggest issues in solar flare modeling. Dynamic range limitations prevent simultaneous spectroscopy with a single instrument of all X-ray emitting regions of a flare. In addition, most X-ray observations so far are inconsistent with the high anisotropy predicted by the models usually adopted for solar flares. Operated at the same time as the STIX instrument of the ESA Solar Orbiter mission, at the next solar maximum (2020), they will have the unique opportunity to look at the same flare from two different directions: Solar Orbiter gets very close to the Sun wit...

  18. The first observed stellar X-ray flare oscillation: Constraints on the flare loop length and the magnetic field

    E-Print Network [OSTI]

    U. Mitra-Kraev; L. K. Harra; D. R. Williams; E. Kraev

    2005-03-17

    We present the first X-ray observation of an oscillation during a stellar flare. The flare occurred on the active M-type dwarf AT Mic and was observed with XMM-Newton. The soft X-ray light curve (0.2-12 keV) is investigated with wavelet analysis. The flare's extended, flat peak shows clear evidence for a damped oscillation with a period of around 750 s, an exponential damping time of around 2000 s, and an initial, relative peak-to-peak amplitude of around 15%. We suggest that the oscillation is a standing magneto-acoustic wave tied to the flare loop, and find that the most likely interpretation is a longitudinal, slow-mode wave, with a resulting loop length of (2.5 +- 0.2) e10 cm. The local magnetic field strength is found to be (105 +- 50) G. These values are consistent with (oscillation-independent) flare cooling time models and pressure balance scaling laws. Such a flare oscillation provides an excellent opportunity to obtain coronal properties like the size of a flare loop or the local magnetic field strength for the otherwise spatially-unresolved star.

  19. Solar Flare Chromospheric Line Emission: Comparison Between IBIS High-resolution Observations and Radiative Hydrodynamic Simulations

    E-Print Network [OSTI]

    da Costa, Fatima Rubio; Petrosian, Vahé; Dalda, Alberto Sainz; Liu, Wei

    2014-01-01

    Solar flares involve impulsive energy release, which results in enhanced radiation in a broad spectral and at a wide height range. In particular, line emission from the chromosphere (lower atmosphere) can provide critical diagnostics of plasma heating processes. Thus, a direct comparison between high-resolution spectroscopic observations and advanced numerical modeling results can be extremely valuable, but has not been attempted so far. We present in this paper such a self-consistent investigation of an M3.0 flare observed by the Dunn Solar Telescope's (DST) Interferometric Bi-dimensional Spectrometer (IBIS) on 2011 September 24 that we have modeled with the radiative hydrodynamic code RADYN (Carlsson & Stein 1992, 1997; Abbett & Hawley 1999; Allred et al. 2005). We obtained images and spectra of the flaring region with IBIS in H$\\alpha$ 6563 \\AA\\ and Ca II 8542 \\AA, and with the Reuven Ramaty High Energy Solar Spectroscope Imager (RHESSI) in X-rays. The latter was used to infer the non-thermal elect...

  20. Tsallis non-extensive statistics, intermittent turbulence, SOC and chaos in the solar plasma. Part two: Solar Flares dynamics

    E-Print Network [OSTI]

    L. P. Karakatsanis; G. P. Pavlos; M. N. Xenakis

    2012-04-03

    In the second part of this study and similarly with part one, the nonlinear analysis of the solar flares index is embedded in the non-extensive statistical theory of Tsallis [1]. The triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the solar flares timeseries. Also the multifractal scaling exponent spectrum, the generalized Renyi dimension spectrum and the spectrum of the structure function exponents were estimated experimentally and theoretically by using the entropy principle included in Tsallis non extensive statistical theory, following Arimitsu and Arimitsu [2]. Our analysis showed clearly the following: a) a phase transition process in the solar flare dynamics from high dimensional non Gaussian SOC state to a low dimensional also non Gaussian chaotic state, b) strong intermittent solar corona turbulence and anomalous (multifractal) diffusion solar corona process, which is strengthened as the solar corona dynamics makes phase transition to low dimensional chaos: c) faithful agreement of Tsallis non equilibrium statistical theory with the experimental estimations of i) non-Gaussian probability distribution function, ii) multifractal scaling exponent spectrum and generalized Renyi dimension spectrum, iii) exponent spectrum of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics. e) The solar flare dynamical profile is revealed similar to the dynamical profile of the solar convection zone as far as the phase transition process from SOC to chaos state. However the solar low corona (solar flare) dynamical characteristics can be clearly discriminated from the dynamical characteristics of the solar convection zone.

  1. Onset of electron acceleration in a flare loop

    SciTech Connect (OSTI)

    Sharykin, Ivan; Liu, Siming [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210008 (China); Fletcher, Lyndsay, E-mail: liusm@pmo.ac.cn [School of Physics and Astronomy, SUPA, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

    2014-09-20

    We carried out a detailed analysis of X-ray and radio observations of a simple flare loop that occurred on 2002 August 12, with the impulsive hard X-ray (HXR) light curves dominated by a single pulse. The emission spectra of the early impulsive phase are consistent with an isothermal model in the coronal loop with a temperature reaching several keV. A power-law high-energy spectral tail is evident near the HXR peak time, in accordance with the appearance of footpoints at high energies, and is well correlated with the radio emission. The energy content of the thermal component keeps increasing gradually after the disappearance of this nonthermal component. These results suggest that electron acceleration only covers the central period of a longer and more gradual energy dissipation process and that the electron transport within the loop plays a crucial role in the formation of the inferred power-law electron distribution. The spectral index of power-law photons shows a very gradual evolution, indicating that the electron accelerator is in a quasi-steady state, which is confirmed by radio observations. These results are consistent with the theory of stochastic electron acceleration from a thermal background. Advanced modeling with coupled electron acceleration and spatial transport processes is needed to explain these observations more quantitatively, which may reveal the dependence of the electron acceleration on the spatial structure of the acceleration region.

  2. Evidence that solar flares drive global oscillations in the Sun

    E-Print Network [OSTI]

    C. Karoff; H. Kjeldsen

    2008-03-21

    Solar flares are large explosions on the Sun's surface caused by a sudden release of magnetic energy. They are known to cause local short-lived oscillations travelling away from the explosion like water rings. Here we show that the energy in the solar acoustic spectrum is correlated with flares. This means that the flares drive global oscillations in the Sun in the same way that the entire Earth is set ringing for several weeks after a major earthquake like the December 2004 Sumatra-Andaman Earthquake. The correlation between flares and energy in the acoustic spectrum of disk-integrated sunlight is stronger for high-frequency waves than for ordinary p-modes which are excited by the turbulence in the near surface convection zone immediately beneath the photosphere.

  3. Detecting Solar Neutrino Flare in Megaton and km^3 detectors

    E-Print Network [OSTI]

    Daniele Fargion; Paola Di Giacomo

    2009-01-21

    To foresee a solar flare neutrino signal we infer its upper and lower bound. The upper bound was derived since a few years by general energy equipartition arguments on observed solar particle flare. The lower bound, the most compelling one for any guarantee neutrino signal, is derived by most recent records of hard Gamma bump due to solar flare on January 2005 (by neutral pion decay).The observed gamma flux reflects into a corresponding one for the neutrinos, almost one to one. Therefore we obtain minimal bounds already at the edge of present but quite within near future Megaton neutrino detectors. Such detectors are considered mostly to reveal cosmic supernova background or rare Local Group (few Mpc) Supernovas events. However Megaton or even inner ten Megaton Ice Cube detector at ten GeV threshold may also reveal traces of solar neutrino in hardest energy of solar flares. Icecube, marginally, too. Solar neutrino flavors may shine light on neutrino mixing angles.

  4. Obscuration of Flare Emission by an Eruptive Prominence

    E-Print Network [OSTI]

    Gopalswamy, Nat

    2013-01-01

    We report on the eclipsing of microwave flare emission by an eruptive prominence from a neighboring region as observed by the Nobeyama Radioheliograph at 17 GHz. The obscuration of the flare emission appears as a dimming feature in the microwave flare light curve. We use the dimming feature to derive the temperature of the prominence and the distribution of heating along the length of the filament. We find that the prominence is heated to a temperature above the quiet Sun temperature at 17 GHz. The duration of the dimming is the time taken by the eruptive prominence in passing over the flaring region. We also find evidence for the obscuration in EUV images obtained by the Solar and Heliospheric Observatory (SOHO) mission.

  5. Leukemia cutis resembling a flare-up of psoriasis

    E-Print Network [OSTI]

    Ferreira, Márcia; Caetano, Mónica; Amorim, Isabel; Selores, Manuela

    2006-01-01

    resembling a flare-up of psoriasis Márcia Ferreira, Mónicaof a 64-year-old man with psoriasis who presented with a 4-colored to erythematous, psoriasis-like papules and plaques

  6. Associated Shale Gas- From Flares to Rig Power 

    E-Print Network [OSTI]

    Wallace, Elizabeth Michelle

    2014-10-16

    From September 2011 to July 2013 the percentage of flared associated gas produced in the Bakken shale formation decreased from 36% to 29%. Although the percentage decreased, the volume of associated gas produced has almost tripled to 900 MMcf...

  7. Statistical Models for Solar Flare Interval Distribution in Individual Active Regions

    E-Print Network [OSTI]

    Yuki Kubo

    2008-02-01

    This article discusses statistical models for solar flare interval distribution in individual active regions. We analyzed solar flare data in 55 active regions that are listed in the GOES soft X-ray flare catalog. We discuss some problems with a conventional procedure to derive probability density functions from any data set and propose a new procedure, which uses the maximum likelihood method and Akaike Information Criterion (AIC) to objectively compare some competing probability density functions. We found that lognormal and inverse Gaussian models are more likely models than the exponential model for solar flare interval distribution in individual active regions. The results suggest that solar flares do not occur randomly in time; rather, solar flare intervals appear to be regulated by solar flare mechanisms. We briefly mention a probabilistic solar flare forecasting method as an application of a solar flare interval distribution analysis.

  8. Multi-Thread Hydrodynamic Modeling of a Solar Flare

    E-Print Network [OSTI]

    Harry P. Warren

    2005-07-13

    Past hydrodynamic simulations have been able to reproduce the high temperatures and densities characteristic of solar flares. These simulations, however, have not been able to account for the slow decay of the observed flare emission or the absence of blueshifts in high spectral resolution line profiles. Recent work has suggested that modeling a flare as an sequence of independently heated threads instead of as a single loop may resolve the discrepancies between the simulations and observations. In this paper we present a method for computing multi-thread, time-dependent hydrodynamic simulations of solar flares and apply it to observations of the Masuda flare of 1992 January 13. We show that it is possible to reproduce the temporal evolution of high temperature thermal flare plasma observed with the instruments on the \\textit{GOES} and \\textit{Yohkoh} satellites. The results from these simulations suggest that the heating time-scale for a individual thread is on the order of 200 s. Significantly shorter heating time scales (20 s) lead to very high temperatures and are inconsistent with the emission observed by \\textit{Yohkoh}.

  9. Diagnose Physical Conditions Near the Flare Energy-release Sites from Observations of Solar Microwave Type III Bursts

    E-Print Network [OSTI]

    Tan, Baolin; Meszarosova, Hana; Huang, Guangli

    2015-01-01

    In the physics of solar flares, it is crucial to diagnose the physical conditions near the flare energy-release sites. However, so far it is unclear how do diagnose these physical conditions. Solar microwave type III burst is believed to be a sensitive signature of the primary energy release and electron accelerations in solar flares. This work takes into account the effect of magnetic field on the plasma density and developed s set of formulas which can be used to estimate the plasma density, temperature, magnetic field near the magnetic reconnection site and particle acceleration region, and the velocity and energy of electron beams. We applied these formulas to three groups of microwave type III pairs in a X-class flare, and obtained some reasonable and interesting results. This method can be applied to other microwave type III bursts to diagnose the physical conditions of source regions, and provide some basic information to understand the intrinsic nature and fundamental processes occurring near the flar...

  10. Gamma-Ray Polarimetry of Two X-Class Solar Flares

    E-Print Network [OSTI]

    Steven E. Boggs; W. Coburn; E. Kalemci

    2005-10-19

    We have performed the first polarimetry of solar flare emission at gamma-ray energies (0.2-1 MeV). These observations were performed with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) for two large flares: the GOES X4.8-class solar flare of 2002 July 23, and the X17-class flare of 2003 October 28. We have marginal polarization detections in both flares, at levels of 21% +/- 9% and -11% +/- 5% respectively. These measurements significantly constrain the levels and directions of solar flare gamma-ray polarization, and begin to probe the underlying electron distributions.

  11. Oilfield Flare Gas Electricity Systems (OFFGASES Project)

    SciTech Connect (OSTI)

    Rachel Henderson; Robert Fickes

    2007-12-31

    The Oilfield Flare Gas Electricity Systems (OFFGASES) project was developed in response to a cooperative agreement offering by the U.S. Department of Energy (DOE) and the National Energy Technology Laboratory (NETL) under Preferred Upstream Management Projects (PUMP III). Project partners included the Interstate Oil and Gas Compact Commission (IOGCC) as lead agency working with the California Energy Commission (CEC) and the California Oil Producers Electric Cooperative (COPE). The project was designed to demonstrate that the entire range of oilfield 'stranded gases' (gas production that can not be delivered to a commercial market because it is poor quality, or the quantity is too small to be economically sold, or there are no pipeline facilities to transport it to market) can be cost-effectively harnessed to make electricity. The utilization of existing, proven distribution generation (DG) technologies to generate electricity was field-tested successfully at four marginal well sites, selected to cover a variety of potential scenarios: high Btu, medium Btu, ultra-low Btu gas, as well as a 'harsh', or high contaminant, gas. Two of the four sites for the OFFGASES project were idle wells that were shut in because of a lack of viable solutions for the stranded noncommercial gas that they produced. Converting stranded gas to useable electrical energy eliminates a waste stream that has potential negative environmental impacts to the oil production operation. The electricity produced will offset that which normally would be purchased from an electric utility, potentially lowering operating costs and extending the economic life of the oil wells. Of the piloted sites, the most promising technologies to handle the range were microturbines that have very low emissions. One recently developed product, the Flex-Microturbine, has the potential to handle the entire range of oilfield gases. It is deployed at an oilfield near Santa Barbara to run on waste gas that is only 4% the strength of natural gas. The cost of producing oil is to a large extent the cost of electric power used to extract and deliver the oil. Researchers have identified stranded and flared gas in California that could generate 400 megawatts of power, and believe that there is at least an additional 2,000 megawatts that have not been identified. Since California accounts for about 14.5% of the total domestic oil production, it is reasonable to assume that about 16,500 megawatts could be generated throughout the United States. This power could restore the cost-effectiveness of thousands of oil wells, increasing oil production by millions of barrels a year, while reducing emissions and greenhouse gas emissions by burning the gas in clean distributed generators rather than flaring or venting the stranded gases. Most turbines and engines are designed for standardized, high-quality gas. However, emerging technologies such as microturbines have increased the options for a broader range of fuels. By demonstrating practical means to consume the four gas streams, the project showed that any gases whose properties are between the extreme conditions also could be utilized. The economics of doing so depends on factors such as the value of additional oil recovered, the price of electricity produced, and the alternate costs to dispose of stranded gas.

  12. Optimized Bose-Einstein-condensate production in a dipole trap based on a 1070-nm multifrequency laser: Influence of enhanced two-body loss on the evaporation process

    E-Print Network [OSTI]

    Thomas Lauber; Johannes Kueber; Oliver Wille; Gerhard Birkl

    2011-10-24

    We present an optimized strategy for the production of tightly confined Bose-Einstein condensates (BEC) of 87Rb in a crossed dipole trap with direct loading from a magneto-optical trap. The dipole trap is created with light of a multifrequency fiber laser with a center wavelength of 1070nm. Evaporative cooling is performed by ramping down the laser power only. A comparison of the resulting atom number in an almost pure BEC to the initial atom number and the value for the gain in phase space density per atom lost confirm that this straightforward strategy is very efficient. We observe that the temporal characteristics of evaporation sequence are strongly influenced by power-dependent two-body losses resulting from enhanced optical pumping to the higher-energy hyperfine state. We characterize these losses and compare them to results obtained with a single-frequency laser at 1030nm.

  13. Optimized Bose-Einstein-condensate production in a dipole trap based on a 1070-nm multifrequency laser: Influence of enhanced two-body loss on the evaporation process

    E-Print Network [OSTI]

    Lauber, Thomas; Wille, Oliver; Birkl, Gerhard

    2011-01-01

    We present an optimized strategy for the production of tightly confined Bose-Einstein condensates (BEC) of 87Rb in a crossed dipole trap with direct loading from a magneto-optical trap. The dipole trap is created with light of a multifrequency fiber laser with a center wavelength of 1070nm. Evaporative cooling is performed by ramping down the laser power only. A comparison of the resulting atom number in an almost pure BEC to the initial atom number and the value for the gain in phase space density per atom lost confirm that this straightforward strategy is very efficient. We observe that the temporal characteristics of evaporation sequence are strongly influenced by power-dependent two-body losses resulting from enhanced optical pumping to the higher-energy hyperfine state. We characterize these losses and compare them to results obtained with a single-frequency laser at 1030nm.

  14. Steam System Losses 

    E-Print Network [OSTI]

    Buchanan, M. G.; Sneary, M. L.

    1995-01-01

    % flash loss I 970.3 2. B x % flash loss =Ibs/hr loss Example: 10,000 x 9% =1900 Ibs/hr 10551 3. Lbs/hr loss x 24 =Ibs/day loss Example: _ 900 x 24 =121,600 Ibs/day 10551 4. Lbs/day loss x 365 =Ibs/yr loss Example: 21,600 x 365 =17,884,000 Ibs/yr... 10551 Estimated Dollar Loss: 5. Lbslyr x C = $ loss per year 1000 Example: 7.884.000 x $5.00 = ~39,420 loss per year to flashing I 1000 Estimated Energy Loss: 6. Lbs/yr loss x (F+G) =loss/yr Example: 7,884,000 x (180.70 + 970.30) = 9...

  15. Anti-Neutrino Imprint in Solar Neutrino Flare

    E-Print Network [OSTI]

    D. Fargion

    2006-06-09

    Future neutrino detector at Megaton mass might enlarge the neutrino telescope thresholds revealing cosmic supernova background and largest solar flares neutrino. Indeed the solar energetic flare particles while scattering among themselves on Solar corona atmosphere must produce prompt charged pions, whose chain decays are source of solar (electron-muon) neutrino "flare" (at tens or hundreds MeV energy). These brief (minutes) neutrino "burst" at largest flare peak may overcome by three to five order of magnitude the steady atmospheric neutrino noise on the Earth, possibly leading to their detection above detection. Moreover the birth of anti-neutrinos at a few tens MeVs is well loudly flaring above a null thermal "hep" anti-neutrino solar background and also above a tiny supernova relic and atmospheric noise. The largest prompt solar anti-neutrino "burst" may be well detected in future SuperKamikande (Gadolinium implemented) by anti-neutrino signatures mostly in inverse Beta decay. Our estimate for the recent and exceptional October - November 2003 solar flares and January 20th 2005 exceptional eruption might lead to a few events above or near unity for existing Super-Kamiokande and above unity for Megaton detectors. The neutrino spectra may reflect in a subtle way the neutrino flavor oscillations and mixing in flight. A comparison of the solar neutrino flare (at their birth place on Sun and after oscillation on the arrival on the Earth) with other neutrino foreground is estimated: it offers an independent track to disentangle the neutrino flavor puzzles and its most secret mixing angles. The sharpest noise-free anti-neutrino imprint maybe its first clean voice.

  16. PUBLISHED ONLINE: 2 JULY 2013 | DOI: 10.1038/NPHYS2670 Self-organized criticality in X-ray flares of

    E-Print Network [OSTI]

    Loss, Daniel

    statistical results of X-ray flares of GRBs with known redshifts, and show that X-ray flares and solar flares-organized criticality (SOC) system. The statistical properties of X-ray flares of GRBs are similar to solar flares for the first time. On the other hand, it is well known that solar flares with a timescale of hours

  17. Super-hot (T > 30 MK) Thermal Plasma in Solar Flares

    E-Print Network [OSTI]

    Caspi, Amir

    2010-01-01

    MNRAS, 148, 17 Kane, S. R. , et al. 1980, in Solar Flares: AMonograph from SKYLAB Solar Workshop II, ed. P. A.Moore, R. , et al. 1980, in Solar Flares: A Monograph from

  18. ELECTROMAGNETIC AND CORPUSCULAR EMISSION FROM THE SOLAR FLARE OF 1991 JUNE 15: CONTINUOUS ACCELERATON OF

    E-Print Network [OSTI]

    Usoskin, Ilya G.

    detected previously in only a few ground level events (GLE) detected by the neutron monitor network (e-flare loop system were also recorded. In Figure 1 we show the post-flare loops observed at Big Bear

  19. Space weather effects on the Mars ionosphere due to solar flares and meteors

    E-Print Network [OSTI]

    Withers, Paul

    Space weather effects on the Mars ionosphere due to solar flares and meteors P. Withers (1), M observed two aspects of space weather at Mars. Following solar flares of both moderate to strong magnitude

  20. Multi-Wavelength Observations of the Spatio-Temporal Evolution of Solar Flares with AIA/SDO: II. Hydrodynamic Scaling Laws and Thermal Energies

    E-Print Network [OSTI]

    Aschwanden, Markus J

    2013-01-01

    In this study we measure physical parameters of the same set of 155 M and X-class solar flares observed with AIA/SDO as analyzed in Paper I, by performing a {\\sl differential emission measure (DEM)} analysis to determine the flare peak emission measure $EM_p$, peak temperature $T_p$, electron density $n_p$, and thermal energy $E_{th}$, in addition to the spatial scales $L$, areas $A$, and volumes $V$ measured in Paper I. The parameter ranges for M and X-class flares are: $\\log(EM_p)=47.0-50.5$, $T_p=5.0-17.8$ MK, $n_p=4 \\times 10^9-9 \\times 10^{11}$ cm$^{-3}$, and thermal energies of $E_{th}=1.6 \\times 10^{28}-1.1 \\times 10^{32}$ erg. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law $T_p^2 \\propto n_p L$ and $H \\propto T^{7/2} L^{-2}$ during the peak time $t_p$ of the flare density $n_p$, when energy balance between the heating rate $H$ and the conductive and radiative loss rates is achieved for a short instant, and thus enables the applicability of the RTV scaling law. The applic...

  1. Impulsive Heating of Solar Flare Ribbons Above 10 MK

    E-Print Network [OSTI]

    Simões, Paulo J A; Fletcher, Lyndsay

    2015-01-01

    The chromospheric response to the input of flare energy is marked by extended extreme ultraviolet (EUV) ribbons and hard X-ray (HXR) footpoints. These are usually explained as the result of heating and bremsstrahlung emission from accelerated electrons colliding in the dense chromospheric plasma. We present evidence of impulsive heating of flare ribbons above 10 MK in a two-ribbon flare. We analyse the impulsive phase of SOL2013-11-09T06:38, a C2.6 class event using data from Atmospheric Imaging Assembly (AIA) on board of Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to derive the temperature, emission measure and differential emission measure of the flaring regions and investigate the evolution of the plasma in the flaring ribbons. The ribbons were visible at all SDO/AIA EUV/UV wavelengths, in particular, at 94 and 131 \\AA\\ filters, sensitive to temperatures of 8 MK and 12 MK. Time evolution of the emission measure of the plasma above 10 MK at the ribb...

  2. Repeated X-ray Flaring Activity in Sagittarius A*

    E-Print Network [OSTI]

    Guillaume Belanger; Andrea Goldwurm; Fulvio Melia; Farah Yusef-Zadeh; Philippe Ferrando; Delphine Porquet; Nicolas Grosso; Robert Warwick

    2005-08-19

    Investigating the spectral and temporal characteristics of the X-rays coming from Sagittarius A* (Sgr A*) is essential to our development of a more complete understanding of the emission mechanisms in this supermassive black hole located at the center of our Galaxy. Several X-ray flares with varying durations and spectral features have already been observed from this object. Here we present the results of two long XMM-Newton observations of the Galactic nucleus carried out in 2004, for a total exposure time of nearly 500 ks. During these observations we detected two flares from Sgr A* with peak 2-10 keV luminosities about 40 times (L ~ 9x10^34 erg s?1) above the quiescent luminosity: one on 2004 March 31 and another on 2004 August 31. The first flare lasted about 2.5 ks and the second about 5 ks. The combined fit on the Epic spectra yield photon indeces of about 1.5 and 1.9 for the first and second flare respectively. This hard photon index strongly suggests the presence of an important population of non-thermal electrons during the event and supports the view that the majority of flaring events tend to be hard and not very luminous.

  3. Muon and Tau Neutrinos Spectra from Solar Flares

    E-Print Network [OSTI]

    D. Fargion; F. Moscato

    2004-05-03

    Solar neutrino flares and mixing are considered. Most power-full solar flare as the ones occurred on 23th February 1956, September 29th 1989, 28th October and on 2nd-4th November 2003 are sources of cosmic rays, X, gamma and neutrino bursts. These flares took place both on front or in the edge and in the hidden solar disk. The observed and estimated total flare energy should be a source of a prompt secondary neutrino burst originated, by proton-proton-pion production on the sun itself; a more delayed and spread neutrino flux signal arise by the solar charged flare particles reaching the terrestrial atmosphere. Our first estimates of neutrino signals in largest underground detectors hint for few events in correlation with, gamma,radio onser. Our approximated spectra for muons and taus from these rare solar eruption are shown over the most common background. The muon and tau signature is very peculiar and characteristic over electron and anti-electron neutrino fluxes. The rise of muon neutrinos will be detectable above the minimal muon threshold of 113 MeV. The rarest tau appearence will be possible only for hardest solar neutrino energies above 3.471 GeV

  4. A Unified Computational Model for Solar and Stellar Flares

    E-Print Network [OSTI]

    Allred, Joel C; Carlsson, Mats

    2015-01-01

    We present a unified computational framework which can be used to describe impulsive flares on the Sun and on dMe stars. The models assume that the flare impulsive phase is caused by a beam of charged particles that is accelerated in the corona and propagates downward depositing energy and momentum along the way. This rapidly heats the lower stellar atmosphere causing it to explosively expand and dramatically brighten. Our models consist of flux tubes that extend from the sub-photosphere into the corona. We simulate how flare-accelerated charged particles propagate down one-dimensional flux tubes and heat the stellar atmosphere using the Fokker-Planck kinetic theory. Detailed radiative transfer is included so that model predictions can be directly compared with observations. The flux of flare-accelerated particles drives return currents which additionally heat the stellar atmosphere. These effects are also included in our models. We examine the impact of the flare-accelerated particle beams on model solar and...

  5. On flare predictability based on sunspot group evolution

    E-Print Network [OSTI]

    Korsos, Marianna; Erdelyi, Robert; Baranyi, Tunde

    2015-01-01

    The forecast method introduced by Kors\\'os et al.(2014) is generalised from the horizontal magnetic gradient (GM), defined between two opposite polarity spots, to all spots within an appropriately defined region close to the magnetic neutral line of an active region. This novel approach is not limited to searching for the largest GM of two single spots as in previous methods. Instead, the pre-flare conditions of the evolution of spot groups is captured by the introduction of the weighted horizontal magnetic gradient, or W_GM. This new proxy enables the potential of forecasting flares stronger than M5. The improved capability includes (i) the prediction of flare onset time and (ii) an assessment whether a flare is followed by another event within about 18 hours. The prediction of onset time is found to be more accurate here. A linear relationship is established between the duration of converging motion and the time elapsed from the moment of closest position to that of the flare onset of opposite polarity spot...

  6. The collisional relaxation of electrons in hot flaring plasma and inferring the properties of solar flare accelerated electrons from X-ray observations

    E-Print Network [OSTI]

    Jeffrey, Natasha; Emslie, Gordon; Bian, Nicolas

    2015-01-01

    X-ray observations are a direct diagnostic of fast electrons produced in solar flares, energized during the energy release process and directed towards the Sun. Since the properties of accelerated electrons can be substantially changed during their transport and interaction with the background plasma, a model must ultimately be applied to X-ray observations in order to understand the mechanism responsible for their acceleration. A cold thick target model is ubiquitously used for this task, since it provides a simple analytic relationship between the accelerated electron spectrum and the emitting electron spectrum in the X-ray source, with the latter quantity readily obtained from X-ray observations. However, such a model is inappropriate for the majority of solar flares in which the electrons propagate in a hot megaKelvin plasma, because it does not take into account the physics of thermalization of fast electrons. The use of a more realistic model, properly accounting for the properties of the background pla...

  7. Acceleration and Enrichment of 3He in Impulsive Solar Flares by Electron Firehose Waves

    E-Print Network [OSTI]

    G. Paesold; R. Kallenbach; A. O. Benz

    2002-09-08

    A new mechanism for acceleration and enrichment of 3He during impulsive solar flares is presented. Low-frequency electromagnetic plasma waves excited by the Electron Firehose Instability (EFI) can account for the acceleration of ions up to 1 MeV/amu energies as a single stage process. The EFI arises as a direct consequence of the free energy stored in a temperature anisotropy (T_parallel>T_perp) of the bulk energized electron population during the acceleration process. In contrast to other mechanisms which require special plasma properties, the EFI is an intrinsic feature of the acceleration process of the bulk electrons. Being present as a side effect in the flaring plasma, these waves can account for the acceleration of 3He and 4He while selectively enhancing 3He due to the spectral energy density built up from linear growth. Linearized kinetic theory, analytic models and test-particle simulations have been applied to investigate the ability of the waves to accelerate and fractionate. As waves grow in both directions parallel to the magnetic field, they can trap resonant ions and efficiently accelerate them to the highest energies. Plausible models have been found that can explain the observed energies, spectra and abundances of 3He and 4He.

  8. Automatic Solar Flare Detection Using MLP, RBF and SVM , Frank Y. Shih1

    E-Print Network [OSTI]

    in light curves. In the mean time, solar flares also emit high velocity charged particles that take one1 Automatic Solar Flare Detection Using MLP, RBF and SVM Ming Qu1 , Frank Y. Shih1 , Ju Jing2. The focus of the automatic solar flare detection is on the development of efficient feature

  9. Solar Flare Intermittency and the Earth's Temperature Anomalies Nicola Scafetta1,2

    E-Print Network [OSTI]

    Scafetta, Nicola

    Solar Flare Intermittency and the Earth's Temperature Anomalies Nicola Scafetta1,2 and Bruce J; published 17 June 2003) We argue that Earth's short-term temperature anomalies and the solar flare data sets that corresponds to the one that would be induced by the solar flare intermittency. The mean

  10. LETTER Earth Planets Space, 61, 577580, 2009 Flares and the chromosphere

    E-Print Network [OSTI]

    California at Berkeley, University of

    magnetic field. Key words: Solar flares, solar chromosphere, solar corona, Alfv´en waves. 1. Introduction The chromosphere historically has been the origin of much of what we understand about solar flares. The rea- son of a solar flare appears mainly in the optical and UV continuum, which form in the lower solar atmosphere

  11. Statistical Assessment of Photospheric Magnetic Features in Imminent Solar Flares Predictions

    E-Print Network [OSTI]

    Statistical Assessment of Photospheric Magnetic Features in Imminent Solar Flares Predictions Hui in solar physics to predict solar flares. 1. Introduction Over the past decades, mankind has become more of the primary objectives in space weather research is to predict the occurrence of solar flares and Coronal Mass

  12. Relationship between magnetic power spectrum and flare productivity in solar active regions

    E-Print Network [OSTI]

    Relationship between magnetic power spectrum and flare productivity in solar active regions V day, being equal to 1 when the specific flare productivity is one C1.0 flare per day. The power index.I. Abramenko Big Bear Solar Observatory, 40386 N. Shore Lane, Big Bear City, CA 92314, USA ABSTRACT Power

  13. Modeling atmospheric effects of the September 1859 solar flare B. C. Thomas,1

    E-Print Network [OSTI]

    Jackman, Charles H.

    Modeling atmospheric effects of the September 1859 solar flare B. C. Thomas,1 C. H. Jackman,2 and A. Melott(2007),ModelingatmosphericeffectsoftheSeptember1859 solar flare, Geophys. Res. Lett., 34, L06810 of the work in this area. [3] The solar flare of 1 September 1859 was one of the most intense white

  14. Splinter Proposal for Cool Stars 16 Title: Solar and Stellar Flares

    E-Print Network [OSTI]

    Hudson, Hugh

    Splinter Proposal for Cool Stars 16 Title: Solar and Stellar Flares 1. Names of the session for CS16. Solar and stellar flares have striking similarities, so important parts of the underlying to initiate discussions to bridge this gap, via a splinter session on solar and stellar flares at Cool Stars

  15. A Novel Forecasting System for Solar Particle Events and Flares (FORSPEF)

    E-Print Network [OSTI]

    Anastasiadis, Anastasios

    A Novel Forecasting System for Solar Particle Events and Flares (FORSPEF) A Papaioannou1 Energetic Particles (SEPs) result from intense solar eruptive events such as solar flares and coronal mass. In this work, we present FORSPEF (Forecasting Solar Particle Events and Flares), a novel dual system, designed

  16. GEOMAGNETIC CONSEQUENCES OF THE SOLAR FLARES DURING THE LAST HALE SOLAR CYCLE (II)

    E-Print Network [OSTI]

    GEOMAGNETIC CONSEQUENCES OF THE SOLAR FLARES DURING THE LAST HALE SOLAR CYCLE (II) Georgeta Maris phenomena. We analyze the cyclic variability of solar flares (registered in H and X-ray) and compare)) for the last Hale cycle. The solar cycles 22 and 23 are different in the level of flare activity

  17. Solar Flare Element Abundances from the Solar Assembly for X-rays (SAX) on MESSENGER

    E-Print Network [OSTI]

    Nittler, Larry R.

    Solar Flare Element Abundances from the Solar Assembly for X-rays (SAX) on MESSENGER Brian RV have been analyzed for 526 large flares detected with the Solar Assembly for X-rays (SAX on 2004 August 3 and capture into orbit around Mercury in 2011, SAX has observed hundreds of solar flares

  18. Anisotropic Bremsstrahlung Emission and the form of Regularized Electron Flux Spectra in Solar Flares

    E-Print Network [OSTI]

    Piana, Michele

    ,3 , & John C. Brown4 ABSTRACT The cross-section for bremsstrahlung photon emission in solar flares is in gen is related to the position of the flare on the solar disk and the direction(s) of the pre-collision electrons relative to the local solar vertical. We compare mean electron flux spectra for the flare of August 21

  19. PROPERTIES OF THE ACCELERATION REGIONS IN SEVERAL LOOP-STRUCTURED SOLAR FLARES

    E-Print Network [OSTI]

    Piana, Michele

    PROPERTIES OF THE ACCELERATION REGIONS IN SEVERAL LOOP-STRUCTURED SOLAR FLARES Jingnan Guo1 , A-energy electrons accelerated in solar flares is the hard X-ray bremsstrahlung that they produce as they propagate et al. (2008) analyzed a set of extended coronal flare loops located near the solar limb, and were

  20. A topological analysis of the magnetic breakout model for an eruptive solar flare

    E-Print Network [OSTI]

    Priest, Eric

    A topological analysis of the magnetic breakout model for an eruptive solar flare BY RHONA MACLEAN model gives an elegant explanation for the onset of an eruptive solar flare, involving magnetic types of bifurcation. Keywords: solar flare; magnetic breakout; magnetic topology; solar corona 1

  1. Regularized reconstruction of the differential emission measure from solar flare hard X-ray spectra

    E-Print Network [OSTI]

    Piana, Michele

    Regularized reconstruction of the differential emission measure from solar flare hard X-ray spectra for solar flare hard X-rays, it is currently unclear whether the electron distribution responsible simulated data and real photon spectra recorded by RHESSI. Subject headings: Sun: flares 1. Introduction

  2. Toward magnetic field dissipation during the 23 July 2002 solar flare measured with Solar

    E-Print Network [OSTI]

    Zharkova, Valentina V.

    Toward magnetic field dissipation during the 23 July 2002 solar flare measured with Solar. Benkhalil (2005), Toward magnetic field dissipation during the 23 July 2002 solar flare measured with Solar] It is widely accepted that the source of primary energy release in solar flares is associated with magnetic

  3. Determination of Electron Flux Spectra in a Solar Flare with Ran Augmented Regularization Method: Application

    E-Print Network [OSTI]

    Piana, Michele

    Determination of Electron Flux Spectra in a Solar Flare with Ran Augmented Regularization Method. (2004) have shown how to recover mean source electron spectra F(E) in solar flares through a physical a solar flare observed by RHESSI on 26 February, 2002. Results using different orders of regularization

  4. DOI 10.1007/s11207-015-0710-3 SOLAR AND STELLAR FLARES

    E-Print Network [OSTI]

    Aulanier, Guillaume

    Solar Phys DOI 10.1007/s11207-015-0710-3 SOLAR AND STELLAR FLARES From Coronal Observations to MHD Simulations, the Building Blocks for 3D Models of Solar Flares (Invited Review) M. Janvier1 · G. Aulanier2 · P Abstract Solar flares are energetic events taking place in the Sun's atmosphere, and their effects can

  5. Radio emission from acceleration sites of solar flares , Gregory D. Fleishman1,2

    E-Print Network [OSTI]

    microwave and decimeter continuum bursts may be a signature of the stochastic acceleration in solar flaresRadio emission from acceleration sites of solar flares Yixuan Li1 , Gregory D. Fleishman1 acceleration site of a solar flare. Specifically, we calculate incoherent radio emission produced within two

  6. Dynamic Magnetography of Solar Flaring Loops Gregory D. Fleishman1,2

    E-Print Network [OSTI]

    ) demonstrated that the mean magnetic field in a solar flare derived from the microwave spectrum yields resultsDynamic Magnetography of Solar Flaring Loops Gregory D. Fleishman1,2 , Gelu M. Nita1 , Dale E. Gary with shaking, which allows the derivation of the magnetic field and other parameters along a solar flaring loop

  7. A Reconnecting Current Sheet Imaged in A Solar Flare

    E-Print Network [OSTI]

    Liu, Rui; Wang, Tongjiang; Stenborg, Guillermo; Liu, Chang; Wang, Haimin

    2010-01-01

    Magnetic reconnection changes the magnetic field topology and powers explosive events in astrophysical, space and laboratory plasmas. For flares and coronal mass ejections (CMEs) in the solar atmosphere, the standard model predicts the presence of a reconnecting current sheet, which has been the subject of considerable theoretical and numerical modeling over the last fifty years, yet direct, unambiguous observational verification has been absent. In this Letter we show a bright sheet structure of global length (>0.25 Rsun) and macroscopic width ((5 - 10)x10^3 km) distinctly above the cusp-shaped flaring loop, imaged during the flare rising phase in EUV. The sheet formed due to the stretch of a transequatorial loop system, and was accompanied by various reconnection signatures that have been dispersed in the literature. This unique event provides a comprehensive view of the reconnection geometry and dynamics in the solar corona.

  8. Complex Flare Dynamics Initiated by a Filament-Filament Interaction

    E-Print Network [OSTI]

    Zhu, Chunming; Alexander, David; Sun, Xudong; McAteer, James

    2015-01-01

    We report on an eruption involving a relatively rare filament-filament interaction on 2013 June 21, observed by SDO and STEREO-B. The two filaments were separated in height within AR 11777. The onset of the eruption of the lower filament was accompanied simultaneously by the apparent descent of the upper filament resulting in a convergence and direct interaction of the two filaments. The interaction was accompanied by the heating of plasmas surrounding the upper filament and the subsequent coalescence of the filaments into a magnetically complex structure, whose eruption was associated with an M2.9 class solar flare. Magnetic loop shrinkage and descending dark voids were observed at different locations as part of the large flare energy release giving us a unique insight into these dynamic flare phenomena.

  9. Observations of Electrons from the Decay of Solar Flare Neutrons

    E-Print Network [OSTI]

    W. Dröge; D. Ruffolo; B. Klecker

    1996-04-03

    We have found evidence for fluxes of energetic electrons in interplanetary space on board the ISEE-3 spacecraft which we interpret as the decay products of neutrons generated in a solar flare on 1980 June 21. The decay electrons arrived at the s/c shortly before the electrons from the flare and can be distinguished from the latter by their distinctive energy spectrum. The time profile of the decay electrons is in good agreement with the results from a simulation based on a scattering mean free path derived from a fit to the flare electron data. The comparison with simultaneously observed decay protons and a published direct measurement of high-energy neutrons places important constraints on the parent neutron spectrum.

  10. Energy Partitions and Evolution in a Purely Thermal Solar Flare

    E-Print Network [OSTI]

    Fleishman, Gregory D; Gary, Dale E

    2015-01-01

    This paper presents a solely thermal flare, which we detected in the microwave range from the thermal gyro- and free-free emission it produced. An advantage of analyzing thermal gyro emission is its unique ability to precisely yield the magnetic field in the radiating volume. When combined with observationally-deduced plasma density and temperature, these magnetic field measurements offer a straightforward way of tracking evolution of the magnetic and thermal energies in the flare. For the event described here, the magnetic energy density in the radio-emitting volume declines over the flare rise phase, then stays roughly constant during the extended peak phase, but recovers to the original level over the decay phase. At the stage where the magnetic energy density decreases, the thermal energy density increases; however, this increase is insufficient, by roughly an order of magnitude, to compensate for the magnetic energy decrease. When the magnetic energy release is over, the source parameters come back to ne...

  11. NEUTRINO-COOLED ACCRETION MODEL WITH MAGNETIC COUPLING FOR X-RAY FLARES IN GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Luo Yang; Gu Weimin; Liu Tong; Lu Jufu, E-mail: guwm@xmu.edu.cn [Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China)

    2013-08-20

    The neutrino-cooled accretion disk, which was proposed to work as the central engine of gamma-ray bursts, encounters difficulty in interpreting the X-ray flares after the prompt gamma-ray emission. In this paper, the magnetic coupling (MC) between the inner disk and the central black hole (BH) is taken into consideration. For mass accretion rates around 0.001 {approx} 0.1 M{sub Sun} s{sup -1}, our results show that the luminosity of neutrino annihilation can be significantly enhanced due to the coupling effects. As a consequence, after the gamma-ray emission, a remnant disk with mass M{sub disk} {approx}< 0.5 M{sub Sun} may power most of the observed X-ray flares with the rest frame duration less than 100 s. In addition, a comparison between the MC process and the Blandford-Znajek mechanism is shown on the extraction of BH rotational energy.

  12. Sudden Disappearance of a Small Sunspot Associated with the February 20, 2002 M2.4 Flare

    E-Print Network [OSTI]

    with, solar flares (Severny 1964; Zvereva & Severny 1970; Moore et al. 1984; Kosovichev & Zharkova 1999 the solar surface. Spirock et al. (2002) studied the X20 flare on April 2, 2001, the largest solar flare solar flares. It now becomes clear that with the high cadence (1 minute) and high resolution (1 to 2

  13. FLARE ACTIVITY AND THE STRENGTH OF SOLAR CYCLES Miruna Daniela Popescu, Georgeta Mari, Adrian Oncica, Marilena Mierla

    E-Print Network [OSTI]

    FLARE ACTIVITY AND THE STRENGTH OF SOLAR CYCLES Miruna Daniela Popescu, Georgeta Mari, Adrian The paper evaluates the solar flare activity during the last three 11-year cycles (the period 1976 - 2001). The flare occurrence follows the solar cycle (SC) with some particularities for each class of flares

  14. A STATISTICAL STUDY OF SHEAR MOTION OF THE FOOTPOINTS IN TWO-RIBBON FLARES Yingna Su,1,2

    E-Print Network [OSTI]

    Su, Yingna

    : corona -- Sun: flares -- Sun: magnetic fields -- Sun: UV radiation 1. INTRODUCTION Solar flares can been reported in almost 20 solar flares, which suggests that this motion may be a common feature in solar flares. In this paper we have made a detailed statistical study of the shear motion

  15. EUV Non-thermal Line Broadening and High-energy particles during Solar Flares

    E-Print Network [OSTI]

    Kawate, Tomoko

    2013-01-01

    We have studied the relationship between the location of EUV nonthermal broadening and high-energy particles during the large flares by using EUV imaging spectrometer onboard {\\it Hinode}, Nobeyama Radio Polarimeter, Nobeyama Radioheliograph, and Atmospheric Imaging Assembly onboard {\\it Solar Dynamic Observatory}. We have analyzed the five large flare events which contain thermal rich, intermediate, and thermal poor flares classified by the definition discussed in the paper. We found that, in the case of thermal rich flares, the nonthermal broadening of \\ion{Fe}{24} occurred at the top of the flaring loop at the beginning of the flares. The source of the 17 GHz microwave is located at the footpoint of the flare loop. On the other hand, in the case of intermediate/thermal poor flares, the nonthermal broadening of \\ion{Fe}{24} occurred at the footpoint of the flare loop at the beginning of the flares. The source of the 17 GHz microwave is located at the top of the flaring loop. We discussed the difference betw...

  16. GRB 060714: No Clear Dividing Line Between Prompt Emission and X-ray Flares

    E-Print Network [OSTI]

    H. A. Krimm; J. Granot; F. Marshal; M. Perri; S. D. Barthelmy; D. N. Burrows; N. Gehrels; P. Mészáros; D. Morris

    2007-04-16

    The long gamma-ray burst GRB 060714 was observed to exhibit a series of five X-ray flares beginning ~70 s after the burst trigger T0 and continuing until T0 + ~200 s. The first two flares were detected by the Burst Alert Telescope (BAT) on the Swift satellite, before Swift had slewed to the burst location, while the last three flares were strongly detected by the X-Ray Telescope (XRT) but only weakly detected by the BAT. This burst provides an unusual opportunity to track a complete sequence of flares over a wide energy range. The flares were very similar in their light curve morphology, showing power-law rise and fall components, and in most cases significant sub-structure. The flares also showed strong evolution with time, both spectrally and temporally. The small time scale and large amplitude variability observed are incompatible with an external shock origin for the flares, and support instead late time sporadic activity either of the central source or of localized dissipation events within the outflow. We show that the flares in GRB 060714 cannot be the result of internal shocks in which the contrast in the Lorentz factor of the colliding shells is very small, and that this mechanism faces serious difficulties in most Swift GRBs. The morphological similarity of the flares and the prompt emission and the gradual and continual evolution of the flares with time makes it difficult and arbitrary to draw a dividing line between the prompt emission and the flares.

  17. Temporal aspects and frequency distributions of solar soft X-ray flares

    E-Print Network [OSTI]

    A. Veronig; M. Temmer; A. Hanslmeier; W. Otruba; M. Messerotti

    2002-07-11

    A statistical analysis of almost 50000 soft X-ray (SXR) flares observed by GOES during the period 1976-2000 is presented. On the basis of this extensive data set, statistics on temporal properties of soft X-ray flares, such as duration, rise and decay times with regard to the SXR flare classes is presented. Correlations among distinct flare parameters, i.e. SXR peak flux, fluence and characteristic times, and frequency distributions of flare occurrence as function of the peak flux, the fluence and the duration are derived. We discuss the results of the analysis with respect to statistical flare models, the idea of coronal heating by nanoflares, and elaborate on implications of the obtained results on the Neupert effect in solar flares.

  18. Prediction of Solar Flares from a Statistical Analysis of Events during Solar Cycle 23

    E-Print Network [OSTI]

    Z. Q. Qu

    2008-11-14

    Ways to give medium- and short-term predictions of solar flares are proposed according to the statistical analysis of events during solar cycle 23. On one hand, the time distribution of both C and M class flares shows two main periods of 13.2 and 26.4 months in this cycle by wavelet analysis. On the other hand, active regions of specific magnetic configurations and their evolutions give high productivity of C class flares but relatively low productivity of energetic (M and X class) flares. Furthermore, by considering the measurable kinetic features of active regions, i.e., the rotation of the sunspots, some active regions of specified types are observed to have high energetic flare productivity, above 66%. The periodicity of the activity revealed can be used for medium-term C and M class flare forecasting and the high productivity of active regions forms the basis for short-term prediction of individual energetic flares.

  19. Relative timing of solar flares observed at different wavelengths

    E-Print Network [OSTI]

    A. Veronig; B. Vrsnak; M. Temmer; A. Hanslmeier

    2002-08-05

    The timing of 503 solar flares observed simultaneously in hard X-rays, soft X-rays and H-alpha is analyzed. We investigated the start and the peak time differences in different wavelengths, as well as the differences between the end of the hard X-ray emission and the maximum of the soft X-ray and H-alpha emission. In more than 90% of the analyzed events, a thermal preheating seen in soft X-rays is present prior to the impulsive flare phase. On average, the soft X-ray emission starts 3 min before the hard X-ray and the H-alpha emission. No correlation between the duration of the preheating phase and the importance of the subsequent flare is found. Furthermore, the duration of the preheating phase does not differ for impulsive and gradual flares. For at least half of the events, the end of the nonthermal emission coincides well with the maximum of the thermal emission, consistent with the beam-driven evaporation model. On the other hand, for about 25% of the events there is strong evidence for prolonged evaporation beyond the end of the hard X-rays. For these events, the presence of an additional energy transport mechanism, most probably thermal conduction, seems to play an important role.

  20. Solar flare impulsive phase emission observed with SDO/EVE

    SciTech Connect (OSTI)

    Kennedy, Michael B.; Milligan, Ryan O.; Mathioudakis, Mihalis; Keenan, Francis P., E-mail: mkennedy29@qub.ac.uk [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN (United Kingdom)

    2013-12-10

    Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log T{sub e} = 5.8-7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10 s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3-4 MK and we use spatially unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied, the DEMs exhibited a two-component distribution during the impulsive phase, a low-temperature component with peak temperature of 1-2 MK, and a broad high-temperature component from 7 to 30 MK. A bimodal high-temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emission was verified using Atmospheric Imaging Assembly images to be the flare ribbons and footpoints, indicating that the constructed DEMs represent the spatially average thermal structure of the chromospheric flare emission during the impulsive phase.

  1. Coronal Trapping of Energetic Flare Particles: Yohkoh/HXT Observations

    E-Print Network [OSTI]

    Metcalf, Thomas R.

    the energization of the solar corona. The most common interpretation for the production of the observed HXR fluxes Alexander Lockheed Martin Solar and Astrophysics Laboratory, Department H1­12, Bldg. 252, 3251 Hanover St in a search for spectral evidence of the coronal trapping of energetic particles during solar flares. Two

  2. Simulations of the Mars ionosphere during a solar flare

    E-Print Network [OSTI]

    Withers, Paul

    .05.23 08:00-10:00 Spring AGU Meeting 2006, Acapulco, Mexico #12;Increased fluxes of X-rays during solarSimulations of the Mars ionosphere during a solar flare Paul Withers, Joei Wroten, Michael Mendillo simulations of the Mars ionosphere driven by temporally-varying solar fluxes, concentrating on 15 and 26 April

  3. Global Energetics of Solar Flares: II. Thermal Energies

    E-Print Network [OSTI]

    Aschwanden, M J; Ryan, D; Caspi, A; McTiernan, J M; Warren, H P

    2015-01-01

    We present the second part of a project on the global energetics of solar flares and CMEs that includes about 400 M- and X-class flares observed with AIA/SDO during the first 3.5 years of its mission. In this Paper II we compute the differential emission measure (DEM) distribution functions and associated multi-thermal energies, using a spatially-synthesized Gaussian DEM forward-fitting method. The multi-thermal DEM function yields a significantly higher (by an average factor of $\\approx 14$), but more comprehensive (multi-)thermal energy than an isothermal energy estimate from the same AIA data. We find a statistical energy ratio of $E_{th}/E_{diss} \\approx 2\\%-40\\%$ between the multi-thermal energy $E_{th}$ and the magnetically dissipated energy $E_{diss}$, which is an order of magnitude higher than the estimates of Emslie et al.~2012. For the analyzed set of M and X-class flares we find the following physical parameter ranges: $L=10^{8.2}-10^{9.7}$ cm for the length scale of the flare areas, $T_p=10^{5.7}-...

  4. Soft X-ray emission in flaring coronal loops

    E-Print Network [OSTI]

    Pinto, R F; Brun, A S

    2014-01-01

    Solar flares are associated with intense soft X-ray emission generated by the hot flaring plasma in coronal magnetic loops. Kink unstable twisted flux-ropes provide a source of magnetic energy which can be released impulsively and account for the heating of the plasma in flares. We investigate the temporal, spectral and spatial evolution of the properties of the thermal X-ray emission produced in such kink-unstable magnetic flux-ropes using a series of MHD simulations. We deduce emission diagnostics and their temporal evolution and discuss the results of the simulations with respect to observations. The numerical setup used consists of a highly twisted loop embedded in a region of uniform and untwisted background coronal magnetic field. We let the kink instability develop, compute the evolution of the plasma properties in the loop (density, temperature) and deduce the X-ray emission properties of the plasma during the whole flaring episode. During the initial phase of the instability plasma heating is mostly ...

  5. Oxygen Loss from Venus and the Influence of Extreme Solar Wind Conditions

    E-Print Network [OSTI]

    McEnulty, Tess

    2012-01-01

    observations of geoeffective solar flare events in Decemberare the location of solar flares and coronal mass ejections

  6. Evaluating Transformer Losses 

    E-Print Network [OSTI]

    Grun, R. L. Jr.

    1989-01-01

    This paper outlines how to determine what transformer losses cost and how to evaluate transformer bids to optimize the investment....

  7. Statistics and classification of the microwave zebra patterns associated with solar flares

    SciTech Connect (OSTI)

    Tan, Baolin; Tan, Chengming; Zhang, Yin [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100012 (China); Mészárosová, H.; Karlický, M., E-mail: bltan@nao.cas.cn [Astronomical Institute of the Academy of Sciences of the Czech Republic, Ondrejov 15165 (Czech Republic)

    2014-01-10

    The microwave zebra pattern (ZP) is the most interesting, intriguing, and complex spectral structure frequently observed in solar flares. A comprehensive statistical study will certainly help us to understand the formation mechanism, which is not exactly clear now. This work presents a comprehensive statistical analysis of a big sample with 202 ZP events collected from observations at the Chinese Solar Broadband Radio Spectrometer at Huairou and the Ond?ejov Radiospectrograph in the Czech Republic at frequencies of 1.00-7.60 GHz from 2000 to 2013. After investigating the parameter properties of ZPs, such as the occurrence in flare phase, frequency range, polarization degree, duration, etc., we find that the variation of zebra stripe frequency separation with respect to frequency is the best indicator for a physical classification of ZPs. Microwave ZPs can be classified into three types: equidistant ZPs, variable-distant ZPs, and growing-distant ZPs, possibly corresponding to mechanisms of the Bernstein wave model, whistler wave model, and double plasma resonance model, respectively. This statistical classification may help us to clarify the controversies between the existing various theoretical models and understand the physical processes in the source regions.

  8. Magnetic Reconnection Rates and Energy Release in a Confined X-class Flare

    E-Print Network [OSTI]

    Veronig, A M

    2015-01-01

    We study the energy-release process in the confined X1.6 flare that occurred on 22 October 2014 in AR 12171. Magnetic-reconnection rates and reconnection fluxes are derived from three different data sets: space-based data from the Atmospheric Imaging Assembly (AIA) 1600 {\\AA} filter onboard the Solar Dynamics Observatory (SDO) and ground-based H$\\alpha$ and Ca II K filtergrams from Kanzelh\\"ohe Observatory. The magnetic-reconnection rates determined from the three data sets all closely resemble the temporal profile of the hard X-rays measured by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), which are a proxy for the flare energy released into high-energy electrons. The total magnetic-reconnection flux derived lies between $4.1 \\times 10^{21}$ Mx (AIA 1600 {\\AA}) and $7.9 \\times 10^{21}$ Mx (H$\\alpha$), which corresponds to about 2 to 4% of the total unsigned flux of the strong source AR. Comparison of the magnetic-reconnection flux dependence on the GOES class for 27 eruptive events collected fr...

  9. The optical flare and afterglow light curve of GRB 050904 at redshift z=6.29

    E-Print Network [OSTI]

    D. M. Wei; T. Yan; Y. Z. Fan

    2005-12-07

    GRB050904 is very interesting since it is by far the most distant GRB event known to date($z=6.29$). It was reported that during the prompt high energy emission phase, a very bright optical flare was detected, and it was temporal coincident with an X-ray flare. Here we use two models to explain the optical flare, One is the "late internal shock model", in which the optical flare is produced by the synchrotron radiation of the electrons accelerated by the late internal shock, and the X-ray flare is produced by the synchrotron-self-Compton mechanism. The other is the external forward-reverse shock model, in which the optical flare is from the reverse shock emission and the X-ray flare is attributed to the central engine activity. We show that with proper parameters, a bright optical flare can appear in both models. We think the "late internal shock model" is more favored since in this model the optical flash and the X-ray flare have the same origin, which provides a natural explanation of the temporal coincidence of them. In the forward-reverse shock scenario, fits to the optical flare and the late afterglow suggests that the physical parameters of the reverse shock are much different from that of forward shock, as found in modeling the optical flash of GRB 990123 previously.

  10. High-Energy Gamma-Ray Emission From Solar Flares: Summary of Fermi LAT Detections and Analysis of Two M-Class Flares

    E-Print Network [OSTI]

    ,

    2013-01-01

    We present the detections of 19 solar flares detected in high-energy gamma rays (above 100 MeV) with the Fermi Large Area Telescope (LAT) during its first four years of operation. Interestingly, all flares are associated with fairly fast Coronal Mass Ejections (CMEs) and are not all powerful X-ray flares. We then describe the detailed temporal, spatial and spectral characteristics of the first two long-lasting events: the 2011 March 7 flare, a moderate (M3.7) impulsive flare followed by slowly varying gamma-ray emission over 13 hours, and the 2011 June 7 M2.5 flare, which was followed by gamma-ray emission lasting for 2 hours. We compare the Fermi-LAT data with X-ray and proton data measurements from GOES and RHESSI. We argue that a hadronic origin of the gamma rays is more likely than a leptonic origin and find that the energy spectrum of the proton distribution softens after the 2011 March 7 flare, favoring a scenario with continuous acceleration at the flare site. This work suggests that proton acceleratio...

  11. Fermi Solar Flare Observations We propose to continue and expand our work over the last three years to make Fermi solar flare

    E-Print Network [OSTI]

    Nishikawa, Ken-Ichi

    1 Fermi Solar Flare Observations 1. Summary We propose to continue and expand our work over the last three years to make Fermi solar flare data readily available for analysis by the international solar physics community. The two-year time frame of the proposed effort is extremely important for solar

  12. Discovery of 6.035GHz Hydroxyl Maser Flares in IRAS18566+0408

    E-Print Network [OSTI]

    Al-Marzouk, A A; Hofner, P; Kurtz, S; Linz, H; Olmi, L

    2012-01-01

    We report the discovery of 6.035GHz hydroxyl (OH) maser flares toward the massive star forming region IRAS18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8 GHz H2CO) and methanol (6.7 GHz CH3OH) maser flares. The observations were conducted between October 2008 and January 2010 with the 305m Arecibo Telescope in Puerto Rico. We detected two flare events, one in March 2009, and one in September to November 2009. The OH maser flares are not simultaneous with the H2CO flares, but may be correlated with CH3OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH3OH masers in IRAS18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.

  13. DISCOVERY OF 6.035 GHz HYDROXYL MASER FLARES IN IRAS 18566+0408

    SciTech Connect (OSTI)

    Al-Marzouk, A. A.; Araya, E. D.; Hofner, P.; Kurtz, S.; Linz, H.; Olmi, L.

    2012-05-10

    We report the discovery of 6.035 GHz hydroxyl (OH) maser flares toward the massive star-forming region IRAS 18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8 GHz H{sub 2}CO) and methanol (6.7 GHz CH{sub 3}OH) maser flares. The observations were conducted between 2008 October and 2010 January with the 305 m Arecibo Telescope in Puerto Rico. We detected two flare events, one in 2009 March and one in 2009 September to November. The OH maser flares are not simultaneous with the H{sub 2}CO flares, but may be correlated with CH{sub 3}OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH{sub 3}OH masers in IRAS 18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.

  14. The Acceleration of Ions in Solar Flares During Magnetic Reconnection

    E-Print Network [OSTI]

    Knizhnik, Kalman; Drake, James F

    2011-01-01

    The acceleration of solar flare ions during magnetic reconnection is explored via particle-in-cell simulations that self-consistently follow the motions of both protons and $\\alpha$ particles. We demonstrate that the dominant ion heating during reconnection with a guide field (a magnetic component perpendicular to the reconnection plane) results from pickup behavior during the entry into reconnection exhausts. In contrast with anti-parallel reconnection, the temperature increment is dominantly transverse, rather than parallel, to the local magnetic field. The comparison of protons and alphas reveals a mass-to-charge ($M/Q$) threshold in pickup behavior that favors heating of high $M/Q$ ions over protons, which is consistent with impulsive flare observations.

  15. Slow Magnetoacoustic Oscillations in the Microwave Emission of Solar Flares

    E-Print Network [OSTI]

    Kim, Sujin; Shibasaki, K

    2013-01-01

    Analysis of the microwave data, obtained in the 17 GHz channel of the Nobeyama Radioheliograph during the M1.6 flare on 4th Nov 2010, revealed the presence of 11.8-min oscillations of the emitting plasma density. The oscilla- tions decayed with the characteristic time of about 25-min. These oscillations are also well-seen in the variation of EUV emission intensity measured in the 335 A channel of SDO/AIA. The observed properties of the oscillations are consistent with the properties of so-called SUMER oscillations, observed in the EUV and soft X-ray bands usually as a periodic Doppler shift. The accepted interpretation of SUMER oscillations is a standing slow magnetoacoustic wave. Our analysis presents the first direct observation of the slow magnetoacoustic oscillations in the microwave emission of a solar flare.

  16. LHC Beam Loss Monitors

    E-Print Network [OSTI]

    Arauzo-Garcia, A; Ferioli, G; Gschwendtner, E

    2001-01-01

    At the Large Hadron Collider (LHC) a beam loss system will be installed for a continuous surveillance of particle losses. These beam particles deposit their energy in the super-conducting coils leading to temperature increase, possible magnet quenches and damages. Detailed simulations have shown that a set of six detectors outside the cryostats of the quadrupole magnets in the regular arc cells are needed to completely diagnose the expected beam losses and hence protect the magnets. To characterize the quench levels different loss rates are identified. In order to cover all possible quench scenarios the dynamic range of the beam loss monitors has to be matched to the simulated loss rates. For that purpose different detector systems (PIN-diodes and ionization chambers) are compared.

  17. Max '91: flare research at the next solar maximum

    SciTech Connect (OSTI)

    Dennis, B.; Canfield, R.; Bruner, M.; Emslie, G.; Hildner, E.; Hudson, H.; Hurford, G.; Lin, R.; Novick, R.; Tarbell, T.

    1988-01-01

    To address the central scientific questions surrounding solar flares, coordinated observations of electromagnetic radiation and energetic particles must be made from spacecraft, balloons, rockets, and ground-based observatories. A program to enhance capabilities in these areas in preparation for the next solar maximum in 1991 is recommended. The major scientific issues are described, and required observations and coordination of observations and analyses are detailed. A program plan and conceptual budgets are provided.

  18. Notes of frequency of occurence and energetics of the solar-type stellar flares

    E-Print Network [OSTI]

    Gershberg, R E

    2015-01-01

    On the basis of the 30-year ago ground-based photometry and the recent Kepler space experiment there have been considered frequencies of occurrence and energetics of the solar-type stellar flares. It was concluded that frequencies of occurrence of such flares are proportional to sizes of stellar surfaces, and estimates of maximum flare radiation from the results of the ground-based photometry and space observations practically coincide.

  19. HARD X-RAY AND MICROWAVE FLUX SPECTRA OF THE 2 NOVEMBER 1991 SOLAR FLARE

    E-Print Network [OSTI]

    HARD X-RAY AND MICROWAVE FLUX SPECTRA OF THE 2 NOVEMBER 1991 SOLAR FLARE CHIK-YIN LEE1,2 and HAIMIN analysed the hard X-ray and microwave flux spectra of the solar flare (BATSE No. 1791) on 2 November 1991 for this study. This paper studies the hard X-ray and microwave spectra of the solar flare on 2 November 1991

  20. Seismic Emissions from a Highly Impulsive M6.7 Solar Flare

    E-Print Network [OSTI]

    J. C. Martinez-Oliveros; H. Moradi; A-C. Donea

    2008-01-09

    On 10 March 2001 the active region NOAA 9368 produced an unusually impulsive solar flare in close proximity to the solar limb. This flare has previously been studied in great detail, with observations classifying it as a type 1 white-light flare with a very hard spectrum in hard X-rays. The flare was also associated with a type II radio burst and coronal mass ejection. The flare emission characteristics appeared to closely correspond with previous instances of seismic emission from acoustically active flares. Using standard local helioseismic methods, we identified the seismic signatures produced by the flare that, to date, is the least energetic (in soft X-rays) of the flares known to have generated a detectable acoustic transient. Holographic analysis of the flare shows a compact acoustic source strongly correlated with the impulsive hard X-ray, visible continuum, and radio emission. Time-distance diagrams of the seismic waves emanating from the flare region also show faint signatures, mainly in the eastern sector of the active region. The strong spatial coincidence between the seismic source and the impulsive visible continuum emission reinforces the theory that a substantial component of the seismic emission seen is a result of sudden heating of the low photosphere associated with the observed visible continuum emission. Furthermore, the low-altitude magnetic loop structure inferred from potential--field extrapolations in the flaring region suggests that there is a significant inverse correlation between the seismicity of a flare and the height of the magnetic loops that conduct the particle beams from the corona.

  1. Interacting CMEs and their associated flare and SEP activities

    E-Print Network [OSTI]

    Shanmugaraju, A

    2015-01-01

    We have analyzed a set of 25 interacting events which are associated with the DH type II bursts. These events are selected from the Coronal Mass Ejections observed during the period 1997-2010 in SOHO/LASCO and DH type IIs in Wind/WAVES. Their pre and primary CMEs from nearby active regions are identified using LASCO and EIT images and their height-time diagrams. Their interacting time and height are obtained, and their associated activities, such as, flares and solar energetic particles (>10pfu) are also investigated. Results from the analysis are: primary CMEs are much faster than the pre-CMEs, their X-ray flares are also stronger (X and M class) compared to the flares (C and M class) of pre-CMEs. Most of the events occurred during the period 2000-2006. From the observed width and speed of pre and primary CMEs, the pre-CMEs are found to be less energetic than the primary CMEs. While the primary CMEs are tracked up to the end of LASCO field of view, most of the pre-CMEs are tracked up to < 26Rs. The SEP in...

  2. Magnetic Energy Dissipation during the 2014 March 29 Solar Flares

    E-Print Network [OSTI]

    Aschwanden, Markus J

    2015-01-01

    We calculated the time evolution of the free magnetic energy during the 2014-Mar-29 flare (SOL2014-03-29T17:48), the first X-class flare detected by IRIS. The free energy was calculated from the difference between the nonpotential field, constrained by the geometry of observed loop structures, and the potential field. We use AIA/SDO and IRIS images to delineate the geometry of coronal loops in EUV wavelengths, as well as to trace magnetic field directions in UV wavelengths in the chromosphere and transition region. We find an identical evolution of the free energy for both the coronal and chromospheric tracers, as well as agreement between AIA and IRIS results, with a peak free energy of $E_{free}(t_{peak}) \\approx (45 \\pm 2) \\times 10^{30}$ erg, which decreases by an amount of $\\Delta E_{free} \\approx (29 \\pm 3) \\times 10^{30}$ erg during the flare decay phase. The consistency of free energies measured from different EUV and UV wavelengths for the first time here, demonstrates that vertical electric currents...

  3. Exploring the connection between coronal and footpoint sources in a thin-thick target solar flare model

    E-Print Network [OSTI]

    Marina Battaglia; Arnold O. Benz

    2007-02-12

    Context: Hard X-ray emission of coronal sources in solar flares has been observed and studied since its discovery in Yohkoh observations. Several models have been proposed to explain the physical mechanisms causing this emission and the relations between those sources and simultaneously observed footpoint sources. Aims: We investigate and test one of the models (intermediate thin-thick target model) developed on the basis of Yohkoh observations. The model makes precise predictions on the shape of coronal and footpoint spectra and the relations between them, that can be tested with new instruments such as RHESSI. Methods: RHESSI observations of well observed events are studied in imaging and spectroscopy and compared to the predictions from the intermediate thin-thick target model. Results: The results indicate that such a simple model cannot account for the observed relations between the non-thermal spectra of coronal and footpoint sources. Including non-collisional energy loss of the electrons in the flare loop due to an electric field can solve most of the inconsistencies.

  4. Observation of solar flares through the ART-P telescope side shield

    E-Print Network [OSTI]

    A. Lutovinov; M. Pavlinsky; S. Grebenev

    2001-06-13

    Some preliminary results of observations of six solar flares though the ART-P telescop side shield in 1990-1992 are presented.

  5. Space weather effects on the Mars ionosphere due to solar flares and

    E-Print Network [OSTI]

    Withers, Paul

    Space weather effects on the Mars ionosphere due to solar flares and meteors Paul Withers1, Michael in the ionospheric response to these aspects of space weather. #12;

  6. The Flare Activity of SgrA*; New Coordinated mm to X-Ray Observations

    E-Print Network [OSTI]

    A. Eckart; F. K. Baganoff; R. Schoedel; M. Morris; R. Genzel; G. C. Bower; D. Marrone; J. M. Moran; T. Viehmann; M. W. Bautz; W. N. Brandt; G. P. Garmire; T. Ott; S. Trippe; G. R. Ricker; C. Straubmeier; D. A. Roberts; F. Yusef-Zadeh; J. H. Zhao; R. Rao

    2005-12-16

    We report new simultaneous near-infrared/sub-millimeter/X-ray observations of the SgrA* counterpart associated with the massive 3-4x10**6 solar mass black hole at the Galactic Center. The main aim is to investigate the physical processes responsible for the variable emission from SgrA*. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope and the ACIS-I instrument aboard the Chandra X-ray Observatory as well as the Submillimeter Array SMA on Mauna Kea, Hawaii, and the Very Large Array in New Mexico. We detected one moderately bright flare event in the X-ray domain and 5 events at infrared wavelengths.

  7. Global energetics of solar flares. I. Magnetic energies

    SciTech Connect (OSTI)

    Aschwanden, Markus J.; Xu, Yan; Jing, Ju E-mail: yan.xu@njit.edu

    2014-12-10

    We present the first part of a project on the global energetics of solar flares and coronal mass ejections that includes about 400 M- and X-class flares observed with Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). We calculate the potential (E{sub p} ), the nonpotential (E {sub np}) or free energies (E {sub free} = E {sub np} – E{sub p} ), and the flare-dissipated magnetic energies (E {sub diss}). We calculate these magnetic parameters using two different NLFFF codes: the COR-NLFFF code uses the line-of-sight magnetic field component B{sub z} from HMI to define the potential field, and the two-dimensional (2D) coordinates of automatically detected coronal loops in six coronal wavelengths from AIA to measure the helical twist of coronal loops caused by vertical currents, while the PHOT-NLFFF code extrapolates the photospheric three-dimensional (3D) vector fields. We find agreement between the two codes in the measurement of free energies and dissipated energies within a factor of ? 3. The size distributions of magnetic parameters exhibit powerlaw slopes that are approximately consistent with the fractal-diffusive self-organized criticality model. The magnetic parameters exhibit scaling laws for the nonpotential energy, E{sub np}?E{sub p}{sup 1.02}, for the free energy, E{sub free}?E{sub p}{sup 1.7} and E{sub free}?B{sub ?}{sup 1.0}L{sup 1.5}, for the dissipated energy, E{sub diss}?E{sub p}{sup 1.6} and E{sub diss}?E{sub free}{sup 0.9}, and the energy dissipation volume, V?E{sub diss}{sup 1.2}. The potential energies vary in the range of E{sub p} = 1 × 10{sup 31}-4 × 10{sup 33} erg, while the free energy has a ratio of E {sub free}/E{sub p} ? 1%-25%. The Poynting flux amounts to F {sub flare} ? 5 × 10{sup 8}-10{sup 10} erg cm{sup –2} s{sup –1} during flares, which averages to F {sub AR} ? 6 × 10{sup 6} erg cm{sup –2} s{sup –1} during the entire observation period and is comparable with the coronal heating rate requirement in active regions.

  8. Robust Aerial Object Tracking in Images with Lens Flare Andreas Nussberger1, Helmut Grabner1 and Luc Van Gool1

    E-Print Network [OSTI]

    Grabner, Helmut

    often result in a high number of false detections. Depending on the solar radiation lens flares are very the date, time, position and attitude of the observer we predict the lens flare direction within the image

  9. The contribution of microbunching instability to solar flare emission in the GHz to THz range of frequencies

    SciTech Connect (OSTI)

    Michael Klopf, J. [Department of Applied Science, College of William and Mary, McGlothlin-Street Hall, Williamsburg, VA 23187 (United States); Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sérgio [Centro de Rádio-Astronomia e Astrofísica Mackenzie, Escola de Engenharia, Universidade Presbiteriana Mackenzie, Rua Consolação 896, São Paulo, SP 01302-907 (Brazil)

    2014-08-10

    Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed 'double spectra'. Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.

  10. The contribution of microbunching instability to solar flare emission in the GHz to THz range of frequencies

    SciTech Connect (OSTI)

    Klopf, J. Michael [William and Mary College; Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sergio

    2014-07-01

    Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed "double spectra." Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.

  11. Temporal Evolution of Free Magnetic Energy Associated with Four X-class Flares

    E-Print Network [OSTI]

    energy for much of the solar activity such as flares and coronal mass ejections (CMEs)(see, for review magnetic configuration for conversion into kinetic and/or thermal energy) and its temporal variationTemporal Evolution of Free Magnetic Energy Associated with Four X-class Flares Ju Jing1 , P. F

  12. ACCELERATION AND ENRICHMENT OF 3 IMPULSIVE SOLAR FLARES BY ELECTRON FIREHOSE

    E-Print Network [OSTI]

    ACCELERATION AND ENRICHMENT OF 3 He IN IMPULSIVE SOLAR FLARES BY ELECTRON FIREHOSE WAVES G. Paesold A new mechanism for acceleration and enrichment of 3 He during impulsive solar flares is presented. Low of the free energy stored in a temperature anisotropy (Te > Te ) of the bulk energized electron population

  13. TRACE and YOHKOH Observations of a White Light Flare Thomas R. Metcalf1

    E-Print Network [OSTI]

    Metcalf, Thomas R.

    . Hudson 2 , and Dana W. Longcope3 ABSTRACT We present observations of a large solar white light flare at 400 km s-1 . This is evidence in favor of particle acceleration models which energize the electrons), are typically the most energetic of solar flares. "White light" refers to continuum emission in excess

  14. HARD X-RAY EMISSIONS FROM PARTIALLY OCCULTED SOLAR FLARES Sam Krucker1

    E-Print Network [OSTI]

    California at Berkeley, University of

    HARD X-RAY EMISSIONS FROM PARTIALLY OCCULTED SOLAR FLARES Sa¨m Krucker1 and R. P. Lin1,2 krucker occulted by the solar limb provide diagnostics of coronal hard X-ray (HXR) emissions in the absence of generally much brighter emissions from footpoints of flare loops. In this paper, a statis- tical survey

  15. Extended decimeter radio emission after large solar flares A.O. Benz a,*, H. Perret a

    E-Print Network [OSTI]

    California at Berkeley, University of

    by extremely intense radio emissions at decimeter wave- lengths. The radio emission continued long afterExtended decimeter radio emission after large solar flares A.O. Benz a,*, H. Perret a , P. Saint; accepted 19 September 2005 Abstract The large solar flares of October and November 2003 were accompanied

  16. Electron-Electron Bremsstrahlung Emission and the Inference of Electron Flux Spectra in Solar Flares

    E-Print Network [OSTI]

    Piana, Michele

    to the hard X-ray emission from solar flares, the latter is normally ignored. Such an omission in the study of hard X-ray spectra from solar flares. With the high-resolution hard X- ray spectra madeElectron-Electron Bremsstrahlung Emission and the Inference of Electron Flux Spectra in Solar

  17. Longrange magnetic couplings between solar flares and coronal mass ejections observed by SDO

    E-Print Network [OSTI]

    Schrijver, Karel

    Longrange magnetic couplings between solar flares and coronal mass ejections observed by SDO between solar flares and coronal mass ejections observed by SDO and STEREO, J. Geophys. Res., 116, A04108 to view much of the solar surface and atmosphere simultaneously and continuously. These nearglobal

  18. NEUTRON AND ELECTROMAGNETIC EMISSIONS DURING THE 1990 MAY 24 SOLAR FLARE

    E-Print Network [OSTI]

    Usoskin, Ilya G.

    NEUTRON AND ELECTROMAGNETIC EMISSIONS DURING THE 1990 MAY 24 SOLAR FLARE L. G. KOCHAROV,* JEONGWOO revised form 15 July, 1994) Abstract. In this paper, we are primarilyconcerned with the solar neutron emission during the 1990 May 24 flare, utilizing the counting rate of the Climax neutron monitor

  19. Calibrated Estimates of the Energy in Major Flares of GRS 1915+105

    E-Print Network [OSTI]

    Punsly, Brian

    2013-01-01

    We analyze the energetics of the major radio flare of October 8 2005 in GRS 1915+105. The flare is of particular interest because it is one of the most luminous and energetic radio flares from a Galactic black hole that has ever been observed. The motivation is two-fold. One, to learn more about the energetics of this most extreme phenomenon and its relationship to the accretion state. The second is to verify if the calibrated estimates of the energy of major radio flares (based on the peak low frequency optically thin flux) derived from flares in the period 1996-2001 in Punsly & Rodriguez (2013), PR13 hereafter, can be used to estimate plasmoid energy beyond this time period. We find evidence that the calibrated curves are still accurate for this strong flare. Furthermore, the physically important findings of PR13 are supported by the inclusion of this flare: the flare energy is correlated with both the intrinsic bolometric X-ray luminosity, $L_{\\mathrm{bol}}$, $\\sim 1$ hour before ejection and $L_{\\math...

  20. MICROWAVE AND HARD XRAY OBSERVATIONS OF FOOTPOINT EMISSION FROM SOLAR FLARES

    E-Print Network [OSTI]

    White, Stephen

    MICROWAVE AND HARD X­RAY OBSERVATIONS OF FOOTPOINT EMISSION FROM SOLAR FLARES M. R. KUNDU Dept radio and X­ray imaging data for two solar flares in order to test the idea that asymmetric microwaves and hard x­rays (HXR) has been known to exist for a long time. This connection is manifested

  1. Free Magnetic Energy and Flare Productivity of Active Regions , Changyi Tan2,3

    E-Print Network [OSTI]

    Free Magnetic Energy and Flare Productivity of Active Regions Ju Jing1 , Changyi Tan2,3 , Yuan Yuan with which we are able to estimate the free magnetic energy stored in the active regions. The magnitude scaling correlation between the free magnetic energy and the soft X-ray flare index of active regions

  2. Seismic Emissions from a Highly Impulsive M6.7 Solar Flare

    E-Print Network [OSTI]

    California at Berkeley, University of

    Seismic Emissions from a Highly Impulsive M6.7 Solar Flare J.C. Mart´inez-Oliveros, H. Moradi, A characteristics appeared to closely correspond with previous instances of seismic emission from acoustically active flares. Using standard local helioseismic methods, we identified the seismic sig- natures produced

  3. Large Solar Flares and their Ionospheric D-region Enhancements Neil R. Thomson and Craig J. Rodger

    E-Print Network [OSTI]

    Otago, University of

    1 Large Solar Flares and their Ionospheric D-region Enhancements Neil R. Thomson and Craig J Division, British Antarctic Survey, Cambridge, UK On 4 November 2003, the largest solar flare ever recorded solar flares the X-ray flux received at the Earth increases dramatically, often within a few minutes

  4. ELECTRON FLUX SPECTRAL IMAGING OF SOLAR FLARES THROUGH REGULARIZED ANALYSIS OF HARD X-RAY SOURCE VISIBILITIES

    E-Print Network [OSTI]

    Piana, Michele

    ELECTRON FLUX SPECTRAL IMAGING OF SOLAR FLARES THROUGH REGULARIZED ANALYSIS OF HARD X-RAY SOURCE a new method for imaging spectroscopy analysis of hard X-ray emission during solar flares. The method the method to a solar flare observed on 2002 February 20 by the RHESSI instrument. The event is characterized

  5. STEREOSCOPIC OBSERVATIONS OF THE HARD X-RAY SOURCE IN THE GIANT SOLAR FLARE ON 2003 NOVEMBER 4

    E-Print Network [OSTI]

    McTiernan, James M.

    STEREOSCOPIC OBSERVATIONS OF THE HARD X-RAY SOURCE IN THE GIANT SOLAR FLARE ON 2003 NOVEMBER 4 S. R Received 2004 June xx; accepted 2004 xxxx xx ABSTRACT The hard X-ray source in the "giant" solar flare on 4 indicated that, in each of the eleven solar flares, the 20 keV non-thermal electrons at the Sun dissipated

  6. Global analysis of active longitudes of solar X-ray flares L. Zhang a,b,c

    E-Print Network [OSTI]

    Usoskin, Ilya G.

    Global analysis of active longitudes of solar X-ray flares L. Zhang a,b,c , K. Mursula a,Ã, I: Solar X-rays Flares Active longitudes a b s t r a c t There is increasing evidence that various called active longitudes. We have earlier analyzed the longitudinal occurrence of solar X-ray flares

  7. Solar Physics with Radio Observations, Proceedings of Nobeyama Symposium 1998, NRO Report Millimeter Interferometer Observations of Flares

    E-Print Network [OSTI]

    White, Stephen

    the current state of millimeter interferometry of solar flares and the issues which can be addressedV--energy electrons in the impulsive phase of solar flares as well as from hot dense plasma in the thermal decay phase. BIMA now consists of 10 antennas and is capable of snapshot imaging of solar flares with excellent

  8. SOLAR FLARE ELEMENT ABUNDANCES FROM THE SOLAR ASSEMBLY FOR X-RAYS (SAX) ON Brian R. Dennis1

    E-Print Network [OSTI]

    Nittler, Larry R.

    SOLAR FLARE ELEMENT ABUNDANCES FROM THE SOLAR ASSEMBLY FOR X-RAYS (SAX) ON MESSENGER Brian R been analyzed for 526 large flares detected with the Solar Assembly for X-rays (SAX) on the Mercury ­ Sun: flares ­ Sun: X-rays, gamma-rays 1. INTRODUCTION The Solar Assembly for X-rays (SAX) is part

  9. Using the Maximum X-ray Flux Ratio and X-ray Background to Predict Solar Flare Class

    E-Print Network [OSTI]

    Winter, Lisa M

    2015-01-01

    We present the discovery of a relationship between the maximum ratio of the flare flux (namely, 0.5-4 Ang to the 1-8 Ang flux) and non-flare background (namely, the 1-8 Ang background flux), which clearly separates flares into classes by peak flux level. We established this relationship based on an analysis of the Geostationary Operational Environmental Satellites (GOES) X-ray observations of ~ 50,000 X, M, C, and B flares derived from the NOAA/SWPC flares catalog. Employing a combination of machine learning techniques (K-nearest neighbors and nearest-centroid algorithms) we show a separation of the observed parameters for the different peak flaring energies. This analysis is validated by successfully predicting the flare classes for 100% of the X-class flares, 76% of the M-class flares, 80% of the C-class flares and 81% of the B-class flares for solar cycle 24, based on the training of the parametric extracts for solar flares in cycles 22-23.

  10. ON THE MECHANICAL ENERGY AVAILABLE TO DRIVE SOLAR FLARES A. N. McClymont and G. H. Fisher

    E-Print Network [OSTI]

    California at Berkeley, University of

    ON THE MECHANICAL ENERGY AVAILABLE TO DRIVE SOLAR FLARES A. N. McClymont and G. H. Fisher Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 Abstract. Where does solar flare energy come from? More, generated in the solar interior, can carry sufficient free energy to power even the largest flares ever

  11. Minimize Boiler Short Cycling Losses, Energy Tips: STEAM, Steam...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    6 Minimize Boiler Short Cycling Losses Boiler "short cycling" occurs when an oversized boiler quickly satisfies process or space heating demands, and then shuts down until heat is...

  12. Looptop and Footpoint Impulsive Hard X-Rays and Stochastic Electron Acceleration in Solar Flares

    E-Print Network [OSTI]

    Vahé Petrosian

    2002-07-22

    The discovery of hard X-rays from tops of flaring loops by the HXT of YOHKOH represents a significant progress in the understanding of solar flares. This report describes the properties of 20 limb flares observed by YOHKOH from October 1991 to August 1998, 15 of which show detectable impulsive looptop emission. Considering the finite dynamic range (about a decade) of the detection it can be concluded that looptop emission is a common feature of all flares. The light curves and images of a representative flare are presented and the statistical properties of the footpoint and looptop fluxes and spectral indexes are summarized. The importance of these observations, and those expected from RHESSI with its superior angular, spectral and temporal resolution, in constraining the acceleration models and parameters is discussed. briefly.

  13. Illinois Natural Gas Vented and Flared (Million Cubic Feet)

    Gasoline and Diesel Fuel Update (EIA)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of Natural GasAdjustments (Billion Cubic Feet)DecadeYear Jan Feb Mar Apr MayYearYear Jan Feb MarMay-15Vented and Flared

  14. Solar Flare Activity Closely Monitored | Department of Energy

    Energy Savers [EERE]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIX E LIST OF APPLICABLE DIRECTIVES PursuantEnergySolar Flare Activity Closely Monitored

  15. Ohio Natural Gas Vented and Flared (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home PageMonthly","10/2015"4,"Ames5 Tables July 1996 Energy Information Administration Office of Coal, Nuclear,DecadeYear JanNew FieldDecade Year-0 Year-1Vented and Flared

  16. Low loss laser glass: Final report

    SciTech Connect (OSTI)

    Izumitani, T.; Toratani, H.; Meissner, H.E.

    1987-01-15

    The objective of this work was a process development on making a laser glass with loss coefficient of 10/sup -4/cm/sup -1/ at 1.05..mu... The key issues for making such a low loss glass will be to use pure raw materials, to reduce OH content and to prevent contamination from the melting environment. A sublimation method was tried to prepare pure P/sub 2/O/sub 5/ batch material. In an attempt to distinguish contributions to the overall loss, glasses were melted in furnaces which were controlled in moisture as well as contamination. Evaluation of glass samples at LLNL are expected to provide guidance on the importance of various process parameters. A new 0.5 liter furnace which almost completely prevents contamination by the furnace environment has been constructed to obtain useful information for making a low loss glass on a production scale.

  17. The connection between mass loss and nucleosynthesis

    E-Print Network [OSTI]

    Jacco Th. van Loon

    2008-01-03

    I discuss the relationship between mass loss and nucleosynthesis on the Asymptotic Giant Branch (AGB). Because of thermal pulses and possibly other mixing processes, products of nucleosynthesis can be brought to the surface of AGB stars, increasingly so as the star becomes more luminous, cooler, and unstable against pulsation of its tenuous mantle. As a result, mass loss is at its most extreme when dredge-up is too. As the high rate of mass loss truncates AGB evolution, it determines the enrichment of interstellar space with the AGB nucleosynthesis products. The changing composition of the stellar atmosphere also affects the mass-loss process, most obviously in the formation of dust grains - which play an important role in driving the wind of AGB stars.

  18. Solar X-ray Flare Hazards on the Surface of Mars

    E-Print Network [OSTI]

    David S. Smith; John M. Scalo

    2006-10-03

    Putative organisms on the Martian surface would be exposed to potentially high doses of ionizing radiation during strong solar X-ray flares. We extrapolate the observed flare frequency-energy release scaling relation to releases much larger than seen so far for the sun, an assumption supported by observations of flares on other solar- and subsolar-mass main sequence stars. We calculate the surficial reprocessed X-ray spectra using a Monte Carlo code we have developed. Biological doses from indirect genome damage are calculated for each parameterized flare spectrum by integration over the X-ray opacity of water. We estimate the mean waiting time for solar flares producing a given biological dose of ionizing radiation on Mars and compare with lethal dose data for a wide range of terrestrial organisms. These timescales range from decades for significant human health risk to 0.5 Myr for D. radiodurans lethality. Such doses require total flare energies of 10^33--10^38 erg, the lower range of which has been observed for other stars. Flares are intermittent bursts, so acute lethality will only occur on the sunward hemisphere during a sufficiently energetic flare, unlike low-dose-rate, extended damage by cosmic rays. We estimate the soil and CO_2 ice columns required to provide 1/e shielding as 4--9 g cm^-2, depending on flare mean energy and atmospheric column density. Topographic altitude variations give a factor of two variation in dose for a given flare. Life in ice layers that may exist ~ 100 g cm^-2 below the surface would be well protected.

  19. Turbulent pitch-angle scattering and diffusive transport of hard X-ray-producing electrons in flaring coronal loops

    SciTech Connect (OSTI)

    Kontar, Eduard P.; Bian, Nicolas H.; Emslie, A. Gordon; Vilmer, Nicole E-mail: emslieg@wku.edu

    2014-01-10

    Recent observations from RHESSI have revealed that the number of non-thermal electrons in the coronal part of a flaring loop can exceed the number of electrons required to explain the hard X-ray-emitting footpoints of the same flaring loop. Such sources cannot, therefore, be interpreted on the basis of the standard collisional transport model, in which electrons stream along the loop while losing their energy through collisions with the ambient plasma; additional physical processes, to either trap or scatter the energetic electrons, are required. Motivated by this and other observations that suggest that high-energy electrons are confined to the coronal region of the source, we consider turbulent pitch-angle scattering of fast electrons off low-frequency magnetic fluctuations as a confinement mechanism, modeled as a spatial diffusion parallel to the mean magnetic field. In general, turbulent scattering leads to a reduction of the collisional stopping distance of non-thermal electrons along the loop, and hence to an enhancement of the coronal hard X-ray source relative to the footpoints. The variation of source size L with electron energy E becomes weaker than the quadratic behavior pertinent to collisional transport, with the slope of L(E) depending directly on the mean free path ? associated with the non-collisional scattering mechanism. Comparing the predictions of the model with observations, we find that ? ? (10{sup 8}-10{sup 9}) cm for ?30 keV, less than the length of a typical flaring loop and smaller than, or comparable to, the size of the electron acceleration region.

  20. Maximum gravitational-wave energy emissible in magnetar flares

    E-Print Network [OSTI]

    Alessandra Corsi; Benjamin J. Owen

    2011-02-16

    Recent searches of gravitational-wave (GW) data raise the question of what maximum GW energies could be emitted during gamma-ray flares of highly magnetized neutron stars (magnetars). The highest energies (\\sim 10^{49} erg) predicted so far come from a model [K. Ioka, Mon. Not. Roy. Astron. Soc. 327, 639 (2001)] in which the internal magnetic field of a magnetar experiences a global reconfiguration, changing the hydromagnetic equilibrium structure of the star and tapping the gravitational potential energy without changing the magnetic potential energy. The largest energies in this model assume very special conditions, including a large change in moment of inertia (which was observed in at most one flare), a very high internal magnetic field, and a very soft equation of state. Here we show that energies of 10^{48}-10^{49} erg are possible under more generic conditions by tapping the magnetic energy, and we note that similar energies may also be available through cracking of exotic solid cores. Current observational limits on gravitational waves from magnetar fundamental modes are just reaching these energies and will beat them in the era of advanced interferometers.

  1. Dynamic Precursors of Flares in Active Region NOAA 10486

    E-Print Network [OSTI]

    Korsos, M B; Baranyi, T; Ludmany, A

    2015-01-01

    Four different methods are applied here to study the precursors of flare activity in the Active Region NOAA 10486. Two approaches track the temporal behaviour of suitably chosen features (one, the weighted horizontal gradient WGM, is generalised form the horizontal gradient of the magnetic field, GM; another is the sum of the horizontal gradient of the magnetic field, GS, for all sunspot pairs). WGM is a photospheric indicator that is a proxy measure of magnetic non-potentiality of a specific area of the active region, i.e. it captures the temporal variation of the weighted horizontal gradient of magnetic flux summed up for the region where opposite magnetic polarities are highly mixed. The third one, referred to as the separateness parameter, S(lf), considers the overall morphology. Further, GS and S(lf) are photospheric newly defined quick-look indicators of the polarity mix of the entire active region. The fourth method is tracking the temporal variation of small x-ray flares, their times of succession and...

  2. MULTI-WAVELENGTH OBSERVATIONS OF THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES WITH AIA/SDO. II. HYDRODYNAMIC SCALING LAWS AND THERMAL ENERGIES

    SciTech Connect (OSTI)

    Aschwanden, Markus J. [Lockheed Martin Advanced Technology Center, Org. ADBS, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304 (United States); Shimizu, Toshifumi, E-mail: aschwanden@lmsal.com, E-mail: shimizu.toshifumi@isas.jaxa.jp [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210 (Japan)

    2013-10-20

    In this study we measure physical parameters of the same set of 155 M- and X-class solar flares observed with AIA/SDO as analyzed in Paper I, by performing a differential emission measure analysis to determine the flare peak emission measure EM{sub p} , peak temperature T{sub p} , electron density n{sub p} , and thermal energy E{sub th}, in addition to the spatial scales L, areas A, and volumes V measured in Paper I. The parameter ranges for M- and X-class flares are log (EM{sub p}) = 47.0-50.5, T{sub p} = 5.0-17.8 MK, n{sub p} = 4 × 10{sup 9}-9 × 10{sup 11} cm{sup –3}, and thermal energies of E{sub th} = 1.6 × 10{sup 28}-1.1 × 10{sup 32} erg. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law T{sub p}{sup 2}?n{sub p} L and H?T {sup 7/2} L {sup –2} during the peak time t{sub p} of the flare density n{sub p} , when energy balance between the heating rate H and the conductive and radiative loss rates is achieved for a short instant and thus enables the applicability of the RTV scaling law. The application of the RTV scaling law predicts power-law distributions for all physical parameters, which we demonstrate with numerical Monte Carlo simulations as well as with analytical calculations. A consequence of the RTV law is also that we can retrieve the size distribution of heating rates, for which we find N(H)?H {sup –1.8}, which is consistent with the magnetic flux distribution N(?)??{sup –1.85} observed by Parnell et al. and the heating flux scaling law F{sub H} ?HL?B/L of Schrijver et al.. The fractal-diffusive self-organized criticality model in conjunction with the RTV scaling law reproduces the observed power-law distributions and their slopes for all geometrical and physical parameters and can be used to predict the size distributions for other flare data sets, instruments, and detection algorithms.

  3. Measurements and modeling of total solar irradiance in X-class solar flares

    SciTech Connect (OSTI)

    Moore, Christopher Samuel; Chamberlin, Phillip Clyde; Hock, Rachel

    2014-05-20

    The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study.

  4. GRB 060714: No Clear Dividing Line Between Prompt Emission and X-ray Flares

    E-Print Network [OSTI]

    Krimm, H A; Marshal, F; Perri, M; Barthelmy, S D; Burrows, D N; Gehrels, N; Mészáros, P; Morris, D

    2007-01-01

    The long gamma-ray burst GRB 060714 was observed to exhibit a series of five X-ray flares beginning ~70 s after the burst trigger T0 and continuing until T0 + ~200 s. The first two flares were detected by the Burst Alert Telescope (BAT) on the Swift satellite, before Swift had slewed to the burst location, while the last three flares were strongly detected by the X-Ray Telescope (XRT) but only weakly detected by the BAT. This burst provides an unusual opportunity to track a complete sequence of flares over a wide energy range. The flares were very similar in their light curve morphology, showing power-law rise and fall components, and in most cases significant sub-structure. The flares also showed strong evolution with time, both spectrally and temporally. The small time scale and large amplitude variability observed are incompatible with an external shock origin for the flares, and support instead late time sporadic activity either of the central source or of localized dissipation events within the outflow. ...

  5. Confined Flares in Solar Active Region 12192 from 2014 October 18 to 29

    E-Print Network [OSTI]

    Chen, Huadong; Ma, Suli; Yang, Shuhong; Li, Leping; Huang, Xin; Xiao, Junmin

    2015-01-01

    Using the observations from the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO), we investigate six X-class and twenty-nine M-class flares occurring in solar active region (AR) 12192 from October 18 to 29. Among them, thirty (including six X- and twenty-four M-class) flares originated from the AR core and the other five M-flares appeared at the AR periphery. Four of the X-flares exhibited similar flaring structures, indicating they were homologous flares with analogous triggering mechanism. The possible scenario is: photospheric motions of emerged magnetic fluxes lead to shearing of the associated coronal magnetic field, which then yields a tether-cutting favorable configuration. Among the five periphery M-flares, four were associated with jet activities. The HMI vertical magnetic field data show that the photospheric fluxes of opposite magnetic polarities emerged, converged and canceled with each other at the footpoints of the jets bef...

  6. Survey on solar X-ray flares and associated coherent radio emissions

    E-Print Network [OSTI]

    Arnold O. Benz; Paolo Grigis; Andre Csillagy; Pascal Saint-Hilaire

    2004-10-19

    The radio emission during 201 X-ray selected solar flares was surveyed from 100 MHz to 4 GHz with the Phoenix-2 spectrometer of ETH Zurich. The selection includes all RHESSI flares larger than C5.0 jointly observed from launch until June 30, 2003. Detailed association rates of radio emission during X-ray flares are reported. In the decimeter wavelength range, type III bursts and the genuinely decimetric emissions (pulsations, continua, and narrowband spikes) were found equally frequently. Both occur predominantly in the peak phase of hard X-ray (HXR) emission, but are less in tune with HXRs than the high-frequency continuum exceeding 4 GHz, attributed to gyrosynchrotron radiation. In 10% of the HXR flares, an intense radiation of the above genuine decimetric types followed in the decay phase or later. Classic meter-wave type III bursts are associated in 33% of all HXR flares, but only in 4% they are the exclusive radio emission. Noise storms were the only radio emission in 5% of the HXR flares, some of them with extended duration. Despite the spatial association (same active region), the noise storm variations are found to be only loosely correlated in time with the X-ray flux. In a surprising 17% of the HXR flares, no coherent radio emission was found in the extremely broad band surveyed. The association but loose correlation between HXR and coherent radio emission is interpreted by multiple reconnection sites connected by common field lines.

  7. Urinary Symptom Flare in 712 {sup 125}I Prostate Brachytherapy Patients: Long-Term Follow-Up

    SciTech Connect (OSTI)

    Keyes, Mira; Miller, Stacy; Moravan, Veronika; Pickles, Tom; Liu, Mitchell; Spadinger, Ingrid; Lapointe, Vincent; Morris, W. James

    2009-11-01

    Purpose: To describe the late transient worsening of urinary symptoms ('urinary symptom flare') in 712 consecutive prostate brachytherapy patients, associated predictive factors, association with rectal and urinary toxicity, and the development of erectile dysfunction. Methods and Materials: Patients underwent implantation between 1998 and 2003 (median follow-up, 57 months). International Prostate Symptom Score (IPSS), Radiation Therapy Oncology Group (RTOG) toxicity, and erectile function data were prospectively collected. Flare was defined as an increase in IPSS of >=5 and of >=8 points greater than the post-treatment nadir. The relationships between the occurrence of flare and the patient, tumor, and treatment characteristics were examined. The Cox proportional hazards method was used to test individual variables and the multivariate models. Results: The incidence of flare was 52% and 30% using the flare definition of an IPSS of >=5 and >=8 points greater than the postimplant nadir, respectively. Of the patients with symptoms, 65% had resolution of their symptoms within 6 months and 91% within 1 year. Flares most commonly occurred 16-24 months after implantation. On multivariate analysis, a greater baseline IPSS and greater maximal postimplant IPSS were the predictors of flare, regardless of the flare definition used. Androgen suppression was a predictor for fewer flares (IPSS >=5). Diabetes and prostate edema predicted for more frequent flares (IPSS >=8). Patients with flare had a greater incidence of RTOG Grade 3 urinary toxicity and RTOG Grade 2 or greater rectal toxicity. No association was found between erectile dysfunction and the occurrence of flare. Conclusion: Urinary symptom flare is a common, transient phenomenon after prostate brachytherapy. A greater baseline IPSS and maximal postimplant IPSS were the strongest predictive factors. Flare was associated with a greater incidence of late RTOG Grade 3 urinary toxicity and greater rate of late RTOG Grade 2 or greater rectal toxicity.

  8. An X-ray, IR, and Submillimeter Flare of Sagittarius A*

    E-Print Network [OSTI]

    D. P. Marrone; F. K. Baganoff; M. R. Morris; J. M. Moran; A. M. Ghez; S. D. Hornstein; C. D. Dowell; D. J. Munoz; M. W. Bautz; G. R. Ricker; W. N. Brandt; G. P. Garmire; J. R. Lu; K. Matthews; J. -H. Zhao; R. Rao; G. C. Bower

    2008-07-14

    Energetic flares are observed in the Galactic supermassive black hole Sagittarius A* from radio to X-ray wavelengths. On a few occasions, simultaneous flares have been detected in IR and X-ray observations, but clear counterparts at longer wavelengths have not been seen. We present a flare observed over several hours on 2006 July 17 with the Chandra X-Ray Observatory, the Keck II telescope, the Caltech Submillimeter Observatory, and the Submillimeter Array. All telescopes observed strong flare events, but the submillimeter peak is found to occur nearly 100 minutes after the X-ray peak. Submillimeter polarization data show linear polarization in the excess flare emission, increasing from 9% to 17% as the flare passes through its peak, consistent with a transition from optically thick to thin synchrotron emission. The temporal and spectral behavior of the flare require that the energetic electrons responsible for the emission cool faster than expected from their radiative output. This is consistent with adiabatic cooling in an expanding emission region, with X-rays produced through self-Compton scattering, although not consistent with the simplest model of such expansion. We also present a submillimeter flare that followed a bright IR flare on 2005 July 31. Compared to 2006, this event had a larger peak IR flux and similar submillimeter flux, but it lacked measurable X-ray emission. It also showed a shorter delay between the IR and submillimeter peaks. Based on these events we propose a synchrotron and self-Compton model to relate the submillimeter lag and the variable IR/X-ray luminosity ratio.

  9. Survivorship Clinic Hearing Loss

    E-Print Network [OSTI]

    Brent, Roger

    of carboplatin High doses of radiation (30 Gy or 3000 cGy/rads or higher) to the head or brain, especially whenSurvivorship Clinic Hearing Loss Some chemotherapy drugs, other medications, or radiation needed are arranged in order of pitch, from low-pitched sounds (such as a man's voice) to very high-pitched sounds

  10. A NEW CORRELATION BETWEEN GRB X-RAY FLARES AND THE PROMPT EMISSION

    SciTech Connect (OSTI)

    Sonbas, E. [Department of Physics, University of Adiyaman, 02040 Adiyaman (Turkey); MacLachlan, G. A.; Shenoy, A.; Dhuga, K. S.; Parke, W. C., E-mail: edasonbas@yahoo.com [Department of Physics, George Washington University, Washington, DC 20052 (United States)

    2013-04-20

    From a sample of gamma-ray bursts (GRBs) detected by the Fermi and Swift missions, we have extracted the minimum variability timescales for temporal structures in the light curves associated with the prompt emission and X-ray flares. A comparison of this variability timescale with pulse parameters such as rise times, determined via pulse-fitting procedures, and spectral lags, extracted via the cross-correlation function, indicates a tight correlation between these temporal features for both the X-ray flares and the prompt emission. These correlations suggest a common origin for the production of X-ray flares and the prompt emission in GRBs.

  11. Simbol-X capability of detecting the non-thermal emission of stellar flares

    E-Print Network [OSTI]

    C. Argiroffi; G. Micela; A. Maggio

    2008-01-16

    We investigate the capability of detecting, with Simbol-X, non-thermal emission during stellar flares, and distinguishing it from hot thermal emission. We find that flare non-thermal emission is detectable when at least ~20 cts are detected with the CZT detector in the 20-80 keV band. Therefore Simbol-X will detect the non-thermal emission from some of the X-ray brightest nearby stars, whether the thermal vs. non-thermal relation, derived for solar flares, holds.

  12. Neutrino Solar Flare detection for a saving alert system of satellites and astronauts

    E-Print Network [OSTI]

    Daniele Fargion

    2011-06-19

    Largest Solar Neutrino Flare may be soon detectable by Deep Core neutrino detector immediately and comunicate to satellites or astronauts. Its detection is the fastest manifestation of a later (tens minutes,hours) dangerous cosmic shower. The precursor trigger maybe saving satellites and even long flight astronauts lives. We shall suggest how. Moreover their detection may probe the inner solar flare acceleration place as well as the neutrino flavor mixing in a new different parameter windows. We show the updated expected rate and signature of neutrinos and antineutrinos in largest solar flare for present tens Megaton Deep Core telescope at tens Gev range. Speculation for additional Icecube gigaton array signals are also considered.

  13. Regularized energy-dependent solar flare hard x-ray spectral index

    E-Print Network [OSTI]

    Eduard P. Kontar; Alexander L. MacKinnon

    2005-06-05

    The deduction from solar flare X-ray photon spectroscopic data of the energy dependent model-independent spectral index is considered as an inverse problem. Using the well developed regularization approach we analyze the energy dependency of spectral index for a high resolution energy spectrum provided by Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The regularization technique produces much smoother derivatives while avoiding additional errors typical of finite differences. It is shown that observations imply a spectral index varying significantly with energy, in a way that also varies with time as the flare progresses. The implications of these findings are discussed in the solar flare context.

  14. Observations and modelling of Helium lines in solar flares

    E-Print Network [OSTI]

    Simões, Paulo J A; Labrosse, Nicolas; Kerr, Graham S

    2015-01-01

    We explore the response of the He II 304 {\\AA} and He I 584 {\\AA} line intensities to electron beam heating in solar flares using radiative hydrodynamic simulations. Comparing different electron beams parameters, we found that the intensities of both He lines are very sensitive to the energy flux deposited in the chromosphere, or more specifically to the heating rate, with He II 304 {\\AA} being more sensitive to the heating than He I 584 {\\AA}. Therefore, the He line ratio increases for larger heating rates in the chromosphere. A similar trend is found in observations, using SDO/EVE He irradiance ratios and estimates of the electron beam energy rate obtained from hard X-ray data. From the simulations, we also found that spectral index of the electrons can affect the He ratio but a similar effect was not found in the observations.

  15. Optimal Electron Energies for Driving Chromospheric Evaporation in Solar Flares

    E-Print Network [OSTI]

    Reep, Jeffrey; Alexander, David

    2015-01-01

    In the standard model of solar flares, energy deposition by a beam of electrons drives strong chromospheric evaporation leading to a significantly denser corona and much brighter emission across the spectrum. Chromospheric evaporation was examined in great detail by Fisher, Canfield, & McClymont (1985a,b,c), who described a distinction between two different regimes, termed explosive and gentle evaporation. In this work, we examine the importance of electron energy and stopping depths on the two regimes and on the atmospheric response. We find that with explosive evaporation, the atmospheric response does not depend strongly on electron energy. In the case of gentle evaporation, lower energy electrons are significantly more efficient at heating the atmosphere and driving up-flows sooner than higher energy electrons. We also find that the threshold between explosive and gentle evaporation is not fixed at a given beam energy flux, but also depends strongly on the electron energy and duration of heating. Furt...

  16. Triggering of Remote Flares by Magnetic Flux Emergence

    E-Print Network [OSTI]

    Fu, Yixing

    2015-01-01

    We study the effect of new emerging solar active regions on the large-scale magnetic environment of existing regions. We first present a theoretical approach to quantify the "interaction energy" between new and pre-existing regions as the difference between (i) the summed magnetic energies of their individual potential fields and (ii) the energy of their superposed potential fields. We expect that this interaction energy can, depending upon the relative arrangements of newly emerged and pre-existing magnetic flux, indicate the existence of "topological" free magnetic energy in the global coronal field that is independent of any "internal" free magnetic energy due to coronal electric currents flowing within the newly emerged and pre-existing flux systems. We then examine the interaction energy in two well-studied cases of flux emergence, but find that the predicted energetic perturbation is relatively small compared to energies released in large solar flares. Next, we present an observational study on the infl...

  17. Combined Modeling of Acceleration, Transport, and Hydrodynamic Response in Solar Flares. II. Inclusion of Radiative Transfer with RADYN

    E-Print Network [OSTI]

    da Costa, Fatima Rubio; Petrosian, Vahe'; Carlsson, Mats

    2015-01-01

    Solar flares involve complex processes that are coupled together and span a wide range of temporal, spatial, and energy scales. Modeling such processes self-consistently has been a challenge in the past. Here we present such a model to simulate the coupling of high-energy particle kinetics with hydrodynamics of the atmospheric plasma. We combine the Stanford unified Fokker-Planck code that models particle acceleration, transport, and bremsstrahlung radiation with the RADYN hydrodynamic code that models the atmospheric response to collisional heating by non-thermal electrons through detailed radiative transfer calculations. We perform simulations using different injection electron spectra, including an {\\it ad hoc} power law and more realistic spectra predicted by the stochastic acceleration model due to turbulence or plasma waves. Surprisingly, stochastically accelerated electrons, even with energy flux $\\ll 10^{10}$ erg s$^{-1}$ cm$^{-2}$, cause "explosive" chromospheric evaporation and drive stronger up- an...

  18. Particle Acceleration in Solar Flares and Enrichment of 3He and Heavy Ions

    E-Print Network [OSTI]

    Vahe' Petrosian

    2008-08-13

    We discuss possible mechanisms of acceleration of particles in solar flares and show that turbulence plays an important role in all the mechanism. It is also argued that stochastic particle acceleration by turbulent plasma waves is the most likely mechanism for production of the high energy electrons and ions responsible for observed radiative signatures of solar flares and for solar energetic particle or SEPs, and that the predictions of this model agrees well with many past and recent high spectral and temporal observations of solar flares. It is shown that, in addition, the model explains many features of SEPs that accompany flares. In particular we show that it can successfully explain the observed extreme enhancement, relative to photospheric values, of $^3$He ions and the relative spectra of $^3$He and $^4$He. It has also the potential of explaining the relative abundances of most ions including the increasing enhancements of heavy ions with ion mass or mass-to-charge ratio.

  19. X-ray flares from dense shells formed in gamma-ray burst explosions

    E-Print Network [OSTI]

    Hascoet, R; Daigne, F; Mochkovitch, R

    2015-01-01

    Bright X-ray flares are routinely detected by the Swift satellite during the early afterglow of gamma-ray bursts, when the explosion ejecta drives a blast wave into the external medium. We suggest that the flares are produced as the reverse shock propagates into the tail of the ejecta. The ejecta is expected to contain a few dense shells formed at an earlier stage of the explosion. We show an example of how such dense shells form and describe how the reverse shock interacts with them. A new reflected shock is generated in this interaction, which produces a short-lived X-ray flare. The model provides a natural explanation for the main observed features of the X-ray flares --- the fast rise, the steep power-law decline, and the characteristic peak duration \\Delta t /t= (0.1-0.3).

  20. RELATIVE ASTROMETRY OF COMPACT FLARING STRUCTURES IN Sgr A* WITH POLARIMETRIC VERY LONG BASELINE INTERFEROMETRY

    E-Print Network [OSTI]

    Johnson, Michael D.

    We demonstrate that polarimetric interferometry can be used to extract precise spatial information about compact polarized flares of Sgr A*. We show that, for a faint dynamical component, a single interferometric baseline ...

  1. Statistical study of free magnetic energy and flare productivity of solar active regions

    SciTech Connect (OSTI)

    Su, J. T.; Jing, J.; Wang, S.; Wang, H. M. [Space Weather Research Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Wiegelmann, T., E-mail: sjt@bao.ac.cn [Max-Planck-Institut fur Sonnensystemforschung, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau (Germany)

    2014-06-20

    Photospheric vector magnetograms from the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory are utilized as the boundary conditions to extrapolate both nonlinear force-free and potential magnetic fields in solar corona. Based on the extrapolations, we are able to determine the free magnetic energy (FME) stored in active regions (ARs). Over 3000 vector magnetograms in 61 ARs were analyzed. We compare FME with the ARs' flare index (FI) and find that there is a weak correlation (<60%) between FME and FI. FME shows slightly improved flare predictability relative to the total unsigned magnetic flux of ARs in the following two aspects: (1) the flare productivity predicted by FME is higher than that predicted by magnetic flux and (2) the correlation between FI and FME is higher than that between FI and magnetic flux. However, this improvement is not significant enough to make a substantial difference in time-accumulated FI, rather than individual flare, predictions.

  2. Correction of SOHO CELIAS/SEM EUV Measurements saturated by extreme solar flare events

    E-Print Network [OSTI]

    L. V. Didkovsky; D. L. Judge; A. R. Jones; S. Wieman; B. T. Tsurutani; D. McMullin

    2006-10-04

    The solar irradiance in the Extreme Ultraviolet (EUV) spectral bands has been observed with a 15 sec cadence by the SOHO Solar EUV Monitor (SEM) since 1995. During remarkably intense solar flares the SEM EUV measurements are saturated in the central (zero) order channel (0.1 -- 50.0 nm) by the flare soft X-ray and EUV flux. The first order EUV channel (26 -- 34 nm) is not saturated by the flare flux because of its limited bandwidth, but it is sensitive to the arrival of Solar Energetic Particles (SEP). While both channels detect nearly equal SEP fluxes, their contributions to the count rate is sensibly negligible in the zero order channel but must be accounted for and removed from the first channel count rate. SEP contribution to the measured SEM signals usually follows the EUV peak for the gradual solar flare events. Correcting the extreme solar flare SEM EUV measurements may reveal currently unclear relations between the flare magnitude, dynamics observed in different EUV spectral bands, and the measured Earth atmosphere response. A simple and effective correction technique based on analysis of SEM count-rate profiles, GOES X-ray, and GOES proton data has been developed and used for correcting EUV measurements for the five extreme solar flare events of July 14, 2000, October 28, November 2, November 4, 2003, and January 20, 2005. Although none of the 2000 and 2003 flare peaks were contaminated by the presence of SEPs, the January 20, 2005 SEPs were unusually prompt and contaminated the peak. The estimated accuracy of the correction is about 7.5% for large X-class events.

  3. High-temperature phase transition in a plasma and the mechanism of powerful solar flares

    E-Print Network [OSTI]

    Fedor V. Prigara

    2006-05-04

    It is shown that the high- temperature phase transition in a plasma gives the mechanism of transition from the highly conductive state to the highly resistive state of a plasma in the `electric circuit' model of solar flares which was first introduced by H.Alfven and P.Carlqvist in 1967. With this addendum, the modern version of the electric circuit model can explain both the fast dissipation of energy and the acceleration of particles in a solar flare.

  4. Underground muons from the direction of Cygnus X-3 during the January 1991 radio flare

    SciTech Connect (OSTI)

    The Soudan 2 Collaboration

    1991-08-01

    Muons recorded in the Soudan 2 underground nucleon decay detector from January 1989 to February 1991 have been examined for any correlation with the radio flares of Cyguns X-3 observed during this period. On two nearby days during the radio flare of January 1991 a total of 32 muons within 2.0{degrees} of the Cyguns X-3 direction were observed when 11.4 were expected.

  5. BEAM LOSS ESTIMATES AND CONTROL FOR THE BNL NEUTRINO FACILITY.

    SciTech Connect (OSTI)

    WENG, W.-T.; LEE, Y.Y.; RAPARIA, D.; TSOUPAS, N.; BEEBE-WANG, J.; WEI, J.; ZHANG, S.Y.

    2005-05-16

    The requirement for low beam loss is very important both to protect the beam component, and to make the hands-on maintenance possible. In this report, the design considerations to achieving high intensity and low loss will be presented. We start by specifying the beam loss limit at every physical process followed by the proper design and parameters for realizing the required goals. The process considered in this paper include the emittance growth in the linac, the H{sup -} injection, the transition crossing, the coherent instabilities and the extraction losses.

  6. Monitoring Energy Losses 

    E-Print Network [OSTI]

    Eulinger, R. D.

    1988-01-01

    Industrial power plants using fossil fuel to produce process steam and electrical energy must be operated at peak efficiency to minimize production costs. Monitoring the power plant operation sometimes takes second place to the primary process...

  7. Radiative hydrodynamic modelling and observations of the X-class solar flare on 2011 March 9

    E-Print Network [OSTI]

    Kennedy, Michael B; Allred, Joel C; Mathioudakis, Mihalis; Keenan, Francis P

    2015-01-01

    We investigated the response of the solar atmosphere to non-thermal electron beam heating using the radiative transfer and hydrodynamics modelling code RADYN. The temporal evolution of the parameters that describe the non-thermal electron energy distribution were derived from hard X-ray observations of a particular flare, and we compared the modelled and observed parameters. The evolution of the non-thermal electron beam parameters during the X1.5 solar flare on 2011 March 9 were obtained from analysis of RHESSI X-ray spectra. The RADYN flare model was allowed to evolve for 110 seconds, after which the electron beam heating was ended, and was then allowed to continue evolving for a further 300s. The modelled flare parameters were compared to the observed parameters determined from extreme-ultraviolet spectroscopy. The model produced a hotter and denser flare loop than that observed and also cooled more rapidly, suggesting that additional energy input in the decay phase of the flare is required. In the explosi...

  8. Hinode Observations of Vector Magnetic Field Change Associated with a Flare on 2006 December 13

    E-Print Network [OSTI]

    Masahito Kubo; Takaaki Yokoyama; Yukio Katsukawa; Bruce W Lites; Saku Tsuneta; Yoshinori Suematsu; Kiyoshi Ichimoto; Toshifumi Shimizu; Shin'ichi Nagata; Theodore D Tarbell; Richard A Shine; Alan M Title; David Elmore

    2007-09-17

    Continuous observations of a flare productive active region 10930 were successfully carried out with the Solar Optical Telescope onboard the Hinode spacecraft during 2007 December 6 to 19. We focus on the evolution of photospheric magnetic fields in this active region, and magnetic field properties at the site of the X3.4 class flare, using a time series of vector field maps with high spatial resolution. The X3.4 class flare occurred on 2006 December 13 at the apparent collision site between the large, opposite polarity umbrae. Elongated magnetic structures with alternatingly positive and negative polarities resulting from flux emergence appeared one day before the flare in the collision site penumbra. Subsequently, the polarity inversion line at the collision site became very complicated. The number of bright loops in Ca II H increased during the formation of these elongated magnetic structures. The flare ribbons and bright loops evolved along the polarity inversion line and one footpoint of the bright loop was located in a region having a large departure of field azimuth angle with respect to its surroundings. The SOT observations with high spatial resolution and high polarization precision reveal temporal change in fine structure of magnetic fields at the flare site: some parts of the complicated polarity inversion line then disappeared, and in those regions the azimuth angle of photospheric magnetic field changed by about 90 degrees, becoming more spatially uniform within the collision site.

  9. A STATISTICAL STUDY OF SPECTRAL HARDENING IN SOLAR FLARES AND RELATED SOLAR ENERGETIC PARTICLE EVENTS

    SciTech Connect (OSTI)

    Grayson, James A.; Krucker, Saem [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States); Lin, R. P., E-mail: jgrayson@berkeley.ed, E-mail: krucker@ssl.berkeley.ed, E-mail: rlin@ssl.berkeley.ed [Also at Department of Physics, University of California, Berkeley, CA 94720-7300 (United States)

    2009-12-20

    Using hard X-ray observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we investigate the reliability of spectral hardening during solar flares as an indicator of related solar energetic particle (SEP) events at Earth. All RHESSI data are analyzed, from 2002 February through the end of Solar Cycle 23, thereby expanding upon recent work on a smaller sample of flares. Previous investigations have found very high success when associating soft-hard-harder (SHH) spectral behavior with energetic proton events, and confirmation of this link would suggest a correlation between electron acceleration in solar flares and SEPs seen in interplanetary space. In agreement with these past findings, we find that of 37 magnetically well-connected flares (W30-W90), 12 of 18 flares with SHH behavior produced SEP events and none of 19 flares without SHH behavior produced SEPs. This demonstrates a statistically significant dependence of SHH and SEP observations, a link that is unexplained in the standard scenario of SEP acceleration at the shock front of coronal mass ejections and encourages further investigation of the mechanisms which could be responsible.

  10. How gas-dynamic flare models powered by Petschek reconnection differ from those with ad hoc energy sources

    E-Print Network [OSTI]

    Longcope, Dana

    2015-01-01

    Aspects of solar flare dynamics, such as chromospheric evaporation and flare light-curves, have long been studied using one-dimensional models of plasma dynamics inside a static flare loop, subjected to some energy input. While extremely successful at explaining the observed characteristics of flares, all such models so far have specified energy input ad hoc, rather than deriving it self-consistently. There is broad consensus that flares are powered by magnetic energy released through reconnection. Recent work has generalized Petschek's basic reconnection scenario, topological change followed by field line retraction and shock heating, to permit its inclusion into a one-dimensional flare loop model. Here we compare the gas dynamics driven by retraction and shocking to those from more conventional static loop models energized by ad hoc source terms. We find significant differences during the first minute, when retraction leads to larger kinetic energies and produces higher densities at the loop top, while ad h...

  11. Fermi Large Area Telescope observations of high-energy gamma-ray emission from behind-the-limb solar flares

    E-Print Network [OSTI]

    Pesce-Rollins, Melissa; Petrosian, Vahe'; Liu, Wei; da Costa, Fatima Rubio; Allafort, Alice

    2015-01-01

    Fermi-LAT >30 MeV observations have increased the number of detected solar flares by almost a factor of 10 with respect to previous space observations. These sample both the impulsive and long duration phases of GOES M and X class flares. Of particular interest is the recent detections of three solar flares whose position behind the limb was confirmed by the STEREO-B spacecraft. While gamma-ray emission up to tens of MeV resulting from proton interactions has been detected before from occulted solar flares, the significance of these particular events lies in the fact that these are the first detections of >100 MeV gamma-ray emission from footpoint-occulted flares. We will present the Fermi-LAT, RHESSI and STEREO observations of these flares and discuss the various emission scenarios for these sources and implications for the particle acceleration mechanisms.

  12. Measurements of Beam Ion Loss from the Compact Helical System

    SciTech Connect (OSTI)

    D. S. Darrow, M. Isobe, Takashi Kondo, M. Sasao, and the CHS Group National Institute for Fusion Science, Toki, Gifu, Japan

    2010-02-03

    Beam ion loss from the Compact Helical System (CHS) has been measured with a scintillator-type probe. The total loss to the probe, and the pitch angle and gyroradius distributions of that loss, have been measured as various plasma parameters were scanned. Three classes of beam ion loss were observed at the probe position: passing ions with pitch angles within 10o of those of transition orbits, ions on transition orbits, and ions on trapped orbits, typically 15o or more from transition orbits. Some orbit calculations in this geometry have been performed in order to understand the characteristics of the loss. Simulation of the detector signal based upon the following of orbits from realistic beam deposition profiles is not able to reproduce the pitch angle distribution of the losses measured. Consequently it is inferred that internal plasma processes, whether magnetohydrodynamic modes, radial electric fields, or plasma turbulence, move previously confined beam ions to transition orbits, resulting in their loss.

  13. 2 Solar flare signatures of the ionospheric GPS total electron content 3 J. Y. Liu,1,2

    E-Print Network [OSTI]

    Chen, Yuh-Ing

    2 Solar flare signatures of the ionospheric GPS total electron content 3 J. Y. Liu,1,2 C. H. Lin,1, ionospheric solar flare effects on the total electron content (TEC) and 7 associated time rate of change (r. The occurrence times and 9 locations of 11 solar flares are isolated from the 1­8 A° X-ray radiations of the 10

  14. Measurement of the rate of stellar tidal disruption flares

    SciTech Connect (OSTI)

    Van Velzen, Sjoert

    2014-09-01

    We report an observational estimate of the rate of stellar tidal disruption flares (TDFs) in inactive galaxies based on a successful search for these events among transients in galaxies using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82). This search yielded 186 nuclear flares in galaxies, 2 of which are excellent TDF candidates. Because of the systematic nature of the search, the very large number of galaxies, the long time of observation, and the fact that non-TDFs were excluded without resorting to assumptions about TDF characteristics, this study provides an unparalleled opportunity to measure the TDF rate. To compute the rate of optical stellar tidal disruption events, we simulate our entire pipeline to obtain the efficiency of detection. The rate depends on the light curves of TDFs, which are presently still poorly constrained. Using only the observed part of the SDSS light curves gives a model-independent upper limit to the optical TDF rate, N-dot <2×10{sup ?4} yr{sup ?1} galaxy{sup ?1} (90% CL), under the assumption that the SDSS TDFs are representative examples. We develop three empirical models of the light curves based on the two SDSS light curves and two more recent and better-sampled Pan-STARRS TDF light curves, leading to our best estimate of the rate: N-dot {sub TDF}=(1.5--2.0){sub ?1.3}{sup +2.7}×10{sup ?5} yr{sup ?1} galaxy{sup ?1}. We explore the modeling uncertainties by considering two theoretically motivated light curve models, as well as two different relationships between black hole mass and galaxy luminosity, and two different treatments of the cutoff in the visibility of TDFs at large M {sub BH}. From this we conclude that these sources of uncertainty are not significantly larger than the statistical ones. Our results are applicable for galaxies hosting black holes with mass in the range of a few 10{sup 6}-10{sup 8} M {sub ?}, and translates to a volumetric TDF rate of (4-8) × 10{sup –8±0.4} yr{sup –1} Mpc{sup –3}, with the statistical uncertainty in the exponent.

  15. Midlatitude Ozone: Loss and Trends

    E-Print Network [OSTI]

    Toohey, Darin W.

    1 Lecture 17 Midlatitude Ozone: Loss and Trends ATOC/CHEM 5151 #12;2 Importance of midlatitude ozone · Covers most of the world's populated areas · Provides protection from UV #12;3 Ozone loss picture, c. 1988 #12;4 Lower vs. Upper stratosphere #12;5 Ozone loss, post 1988 · Discovery of ozone hole

  16. Impulsive phase flare energy transport by large-scale Alfven waves and the electron acceleration problem

    E-Print Network [OSTI]

    L. Fletcher; H. S. Hudson

    2007-12-20

    The impulsive phase of a solar flare marks the epoch of rapid conversion of energy stored in the pre-flare coronal magnetic field. Hard X-ray observations imply that a substantial fraction of flare energy released during the impulsive phase is converted to the kinetic energy of mildly relativistic electrons (10-100 keV). The liberation of the magnetic free energy can occur as the coronal magnetic field reconfigures and relaxes following reconnection. We investigate a scenario in which products of the reconfiguration - large-scale Alfven wave pulses - transport the energy and magnetic-field changes rapidly through the corona to the lower atmosphere. This offers two possibilities for electron acceleration. Firstly, in a coronal plasma with beta waves propagate as inertial Alfven waves. In the presence of strong spatial gradients, these generate field-aligned electric fields that can accelerate electrons to energies on the order of 10 keV and above, including by repeated interactions between electrons and wavefronts. Secondly, when they reflect and mode-convert in the chromosphere, a cascade to high wavenumbers may develop. This will also accelerate electrons by turbulence, in a medium with a locally high electron number density. This concept, which bridges MHD-based and particle-based views of a flare, provides an interpretation of the recently-observed rapid variations of the line-of-sight component of the photospheric magnetic field across the flare impulsive phase, and offers solutions to some perplexing flare problems, such as the flare "number problem" of finding and resupplying sufficient electrons to explain the impulsive-phase hard X-ray emission.

  17. Neutron star blackbody contraction during flaring in X1624-490

    E-Print Network [OSTI]

    M. Balucinska-Church; R. Barnard; M. J. Church; A. P. Smale

    2001-10-01

    We present results of an investigation of the physical changes taking place in the emission regions of the LMXB X1624-490 during strong flaring in RXTE observations. Based on the detailed light curve, we propose that the flaring consists of a superposition of X-ray bursts. It is shown that major changes take place in the blackbody emission component, the temperature kT_BB increasing to ~2.2 keV in flaring. Remarkably, the blackbody area decreases by a factor of ~5 in flaring. During flare evolution, the blackbody luminosity remains approximately constant, constituting a previously unknown Eddington limiting effect which we propose is due to radiation pressure of the blackbody as kT_BB increases affecting the inner disk or accretion flow resulting in a decreased emitting area on the star. We argue that the large decrease in area cannot be explained in terms of modification of the blackbody spectrum by electron scattering in the atmosphere of the neutron star. The height of the emitting region on the non-flaring neutron star is shown to agree with the height of the inner radiatively-supported disk as found for sources in the ASCA survey of LMXB of Church & Balucinska-Church (2001). The decrease in height during flaring is discussed in terms of possible models, including radial accretion flow onto the stellar surface and the theory of accretion flow spreading on the neutron star surface of Inogamov & Sunyaev (1999). We demonstrate that the intensity of the broad iron line at 6.4 keV is strongly correlated with the luminosity of the blackbody emission from the neutron star, and discuss the probable origin of this line in the ADC. Finally, possible reasons for non-detection of a reflection component in this source, and LMXB in general, are discussed.

  18. CONTINUUM CONTRIBUTIONS TO THE SDO/AIA PASSBANDS DURING SOLAR FLARES

    SciTech Connect (OSTI)

    Milligan, Ryan O.; McElroy, Sarah A.

    2013-11-01

    Data from the Multiple EUV Grating Spectrograph component of the Extreme-ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) were used to quantify the contribution of continuum emission to each of the extreme ultraviolet (EUV) channels of the Atmospheric Imaging Assembly (AIA), also on SDO, during an X-class solar flare that occurred on 2011 February 15. Both the pre-flare-subtracted EVE spectra and fits to the associated free-free continuum were convolved with the AIA response functions of the seven EUV passbands at 10 s cadence throughout the course of the flare. It was found that 10%-25% of the total emission in the 94 Å, 131 Å, 193 Å, and 335 Å passbands throughout the main phase of the flare was due to free-free emission. Reliable measurements could not be made for the 171 Å channel, while the continuum contribution to the 304 Å channel was negligible due to the presence of the strong He II emission line. Up to 50% of the emission in the 211 Å channel was found to be due to free-free emission around the peak of the flare, while an additional 20% was due to the recombination continuum of He II. The analysis was extended to a number of M- and X-class flares and it was found that the level of free-free emission contributing to both the 171 Å and 211 Å passbands increased with increasing GOES class. These results suggest that the amount of continuum emission that contributes to AIA observations during flares is more significant than stated in previous studies which used synthetic, rather than observed, spectra. These findings highlight the importance of spectroscopic observations carried out in conjunction with those from imaging instruments so that the data are interpreted correctly.

  19. High-sensitivity observations of solar flare decimeter radiation

    E-Print Network [OSTI]

    Arnold O. Benz; Peter Messmer; Christian Monstein

    2000-12-05

    A new acousto-optic radio spectrometer has observed the 1 - 2 GHz radio emission of solar flares with unprecedented sensitivity. The number of detected decimeter type III bursts is greatly enhanced compared to observations by conventional spectrometers observing only one frequency at the time. The observations indicate a large number of electron beams propagating in dense plasmas. For the first time, we report weak, reversed drifting type III bursts at frequencies above simultaneous narrowband decimeter spikes. The type III bursts are reliable signatures of electron beams propagating downward in the corona, apparently away from the source of the spikes. The observations contradict the most popular spike model that places the spike sources at the footpoints of loops. Conspicuous also was an apparent bidirectional type U burst forming a fish-like pattern. It occurs simultaneously with an intense U-burst at 600-370 MHz observed in Tremsdorf. We suggest that it intermodulated with strong terrestrial interference (cellular phones) causing a spurious symmetric pattern in the spectrogram at 1.4 GHz. Symmetric features in the 1 - 2 GHz range, some already reported in the literature, therefore must be considered with utmost caution.

  20. Electron Acceleration in Solar Flares: Theory of Spectral Evolution

    E-Print Network [OSTI]

    Paolo C. Grigis; Arnold O. Benz

    2006-08-14

    Context: Stochastic acceleration is thought to be a key mechanism in the energization of solar flare electrons. Aims: We study whether stochastic acceleration can reproduce the observed soft-hard-soft evolution of the spectral features of the hard X-ray emitted by suprathermal electron. We pay special attention to the effects of particle trapping and escape. Methods: The Fokker-Planck equation for the electron distribution is integrated numerically using the coefficients derived by Miller et al. for transit-time damping acceleration. The electron spectra are then converted to photon spectra for comparison with RHESSI observation of looptop sources. Results: The presence of particle escape softens the model spectra computed in the stochastic acceleration framework. The ratio between the efficiency of trapping and acceleration controls the spectral evolution which follows a soft-hard-soft pattern. Furthermore, a pivot point (that is, a common crossing point of the accelerated particle spectra at different times) is found at around 10 keV. It can be brought into agreement with the observed value of 20 keV by enhanced trapping through an electric potential. Conclusions: The model proposed here accounts for the key features observed in the spectral evolution of hard X-ray emission from looptop sources.

  1. A HR-like Diagram for Solar/Stellar Flares and Corona -- Emission Measure vs Temperature Diagram

    E-Print Network [OSTI]

    Kazunari Shibata; Takaaki Yokoyama

    2002-06-03

    In our previous paper, we have presented a theory to explain the observed universal correlation between the emission measure ($EM=n^2 V$) and temperature (T) for solar/stellar flares on the basis of the magnetic reconnection model with heat conduction and chromospheric evaporation. Here n is the electron density and V is the volume. By extending our theory to general situations, we examined the EM-T diagram in detail, and found the following properties: 1) The universal correlation sequence (``main sequence flares'') with $EM \\propto T^{17/2}$ corresponds to the case of constant heating flux or equivalently the case of constant magnetic field strength in the reconnection model. 2) The EM-T diagram has a forbidden region, where gas pressure of flares exceeds magnetic pressure. 3) There is a coronal branch with $EM \\propto T^{15/2}$ for $T 10^7$ K. This branch is situated left side of the main sequence flares in the EM-T diagram. 4) There is another forbidden region determined by the length of flare loop; a lower limit of flare loop is $10^7$ cm. Small flares near this limit correspond to nanoflares observed by SOHO/EIT. 5) We can plot flare evolution track on the EM-T diagram. A flare evolves from the coronal branch to main sequence flares, then returns to the coronal branch eventually. These properties of the EM-T diagram are similar to those of the HR diagram for stars, and thus we propose that the EM-T diagram is quite useful to estimate the physical quantities (loop length, heating flux, magnetic field strength, total energy and so on) of flares and corona when there is no spatially resolved imaging observations.

  2. Soot and SO[subscript 2] contribution to the supersites in the MILAGRO campaign from elevated flares in the Tula Refinery

    E-Print Network [OSTI]

    Molina, Luisa Tan

    This work presents a simulation of the plume trajectory emitted by flaring activities of the Miguel Hidalgo Refinery in Mexico. The flame of a representative sour gas flare is modeled with a CFD combustion code in order ...

  3. MAGNETIC NONPOTENTIALITY IN PHOTOSPHERIC ACTIVE REGIONS AS A PREDICTOR OF SOLAR FLARES

    SciTech Connect (OSTI)

    Yang Xiao; Lin Ganghua; Zhang Hongqi; Mao Xinjie

    2013-09-10

    Based on several magnetic nonpotentiality parameters obtained from the vector photospheric active region magnetograms obtained with the Solar Magnetic Field Telescope at the Huairou Solar Observing Station over two solar cycles, a machine learning model has been constructed to predict the occurrence of flares in the corresponding active region within a certain time window. The Support Vector Classifier, a widely used general classifier, is applied to build and test the prediction models. Several classical verification measures are adopted to assess the quality of the predictions. We investigate different flare levels within various time windows, and thus it is possible to estimate the rough classes and erupting times of flares for particular active regions. Several combinations of predictors have been tested in the experiments. The True Skill Statistics are higher than 0.36 in 97% of cases and the Heidke Skill Scores range from 0.23 to 0.48. The predictors derived from longitudinal magnetic fields do perform well, however, they are less sensitive in predicting large flares. Employing the nonpotentiality predictors from vector fields improves the performance of predicting large flares of magnitude {>=}M5.0 and {>=}X1.0.

  4. Solar Neutron Event in Association with a Large Solar Flare on November 24, 2000

    E-Print Network [OSTI]

    K. Watanabe; Y. Muraki; Y. Matsubara; K. Murakami; T. Sako; H. Tsuchiya; S. Masuda; M. Yoshimori; N. Ohmori; P. Miranda; N. Martinic; R. Ticona; A. Velarde; F. Kakimoto; S. Ogio; Y. Tsunesada; H. Tokuno; Y. Shirasaki

    2003-04-03

    Solar neutrons have been detected using the neutron monitor located at Mt. Chacaltaya, Bolivia, in association with a large solar flare on November 24, 2000. This is the first detection of solar neutrons by the neutron monitor that have been reported so far in solar cycle 23. The statistical significance of the detection is 5.5 sigma. In this flare, the intense emission of hard X-rays and gamma-rays has been observed by the Yohkoh Hard X-ray Telescope (HXT) and Gamma Ray Spectrometer (GRS), respectively. The production time of solar neutrons is better correlated with those of hard X-rays and gamma-rays than with the production time of soft X-rays. The observations of the solar neutrons on the ground have been limited to solar flares with soft X-ray class greater than X8 in former solar cycles. In this cycle, however, neutrons were detected associated with an X2.3 solar flare on November 24, 2000. This is the first report of the detection of solar neutrons on the ground associated with a solar flare with its X-ray class smaller than X8.

  5. First Simultaneous NIR/X-ray Detection of a Flare from SgrA*

    E-Print Network [OSTI]

    A. Eckart; F. K. Baganoff; M. Morris; M. W. Bautz; W. N. Brandt; G. P. Garmire; R. Genzel; T. Ott; G. R. Ricker; C. Straubmeier; T. Viehmann; R. Schödel

    2004-06-17

    We report on the first simultaneous near-infrared/X-ray detection of the Sgr A* counterpart which is associated with the massive black hole at the center of the Milky Way. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope and the ACIS-I instrument aboard the Chandra X-ray Observatory. We also report on quasi-simultaneous observations at a wavelength of 3.4 mm using the Berkeley-Illinois-Maryland Association (BIMA) array. A flare was detected in the X-domain with an excess 2-8 keV luminosity of about 6$\\times10^{33}$ erg/s. A fading flare of Sgr A* with $>$2 times the interim-quiescent flux was also detected at the beginning of the NIR observations, that overlapped with the fading part of the X-ray flare. Compared to 8-9 hours before the NIR/X-ray flare we detected a marginally significant increase in the millimeter flux density of Sgr A* during measurements about 7-9 hours afterwards. We find that the flaring state can be conveniently explained with a synchrotron self-Compton model involving up-scattered sub-millimeter photons from a compact source component, possibly with modest bulk relativistic motion. The size of that component is assumed to be of the order of a few times the Schwarzschild radius. The overall spectral indices $\\alpha_{NIR/X-ray}$ ($S_{\

  6. An explanation for long flares from extragalactic globular cluster X-ray sources

    E-Print Network [OSTI]

    Thomas J. Maccarone

    2005-09-21

    Repeatedly flaring X-ray binaries have recently been discovered in NGC 4697 by Sivakoff and collaborators. We show that these flares can be explained as the result of eccentric binaries in globular clusters which accrete more rapidly at periastron than during the rest of the binary orbit. We show that theoretical timescales for producing eccentricities and circularising the binaries are consistent with what is needed to produce the observed population of flaring sources, although the circularisation timescales are highly uncertain on both observational and theoretical grounds. This model makes two clear theoretical predictions (1) the flares should be seen to be strictly periodic if adequate sampling is provided, and that periodicity should be of approximately 15 hours (2) this class of flaring behaviour should be seen only in globular cluster sources, and predominantly in the densest globular clusters. We also test the model for producing eccentricities through fly-by's of a third star near the binary in a globular cluster against a much larger database of millisecond pulsar observations than has been used in past work, and find that the theoretical cross sections for producing eccentricity in binaries are in reasonable agreement with most of the data, provided that the pulsar ages are about $4\\times10^9$ years.

  7. HARD X-RAY AND MICROWAVE EMISSIONS FROM SOLAR FLARES WITH HARD SPECTRAL INDICES

    SciTech Connect (OSTI)

    Kawate, T. [Kwasan and Hida Observatory, Kitashirakawa-oiwakecho, Sakyo, Kyoto 606-8502 (Japan); Nishizuka, N. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 229-8510 (Japan); Oi, A. [College of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Ohyama, M. [Faculty of Education, Shiga University, 2-5-1 Hiratsu, Otsu, Shiga 1-1, Baba Hikone city, Siga 522-8522 (Japan); Nakajima, H., E-mail: kawate@kusastro.kyoto-u.ac.jp [Nobeyama Solar Radio Observatory, NAOJ, Nobeyama, Minamisaku, Nagano 384-1305 (Japan)

    2012-03-10

    We analyze 10 flare events that radiate intense hard X-ray (HXR) emission with significant photons over 300 keV to verify that the electrons that have a common origin of acceleration mechanism and energy power-law distribution with solar flares emit HXRs and microwaves. Most of these events have the following characteristics. HXRs emanate from the footpoints of flare loops, while microwaves emanate from the tops of flare loops. The time profiles of the microwave emission show delays of peak with respect to those of the corresponding HXR emission. The spectral indices of microwave emissions show gradual hardening in all events, while the spectral indices of the corresponding HXR emissions are roughly constant in most of the events, though rather rapid hardening is simultaneously observed in some for both indices during the onset time and the peak time. These characteristics suggest that the microwave emission emanates from the trapped electrons. Then, taking into account the role of the trapping of electrons for the microwave emission, we compare the observed microwave spectra with the model spectra calculated by a gyrosynchrotron code. As a result, we successfully reproduce the eight microwave spectra. From this result, we conclude that the electrons that have a common acceleration and a common energy distribution with solar flares emit both HXR and microwave emissions in the eight events, though microwave emission is contributed to by electrons with much higher energy than HXR emission.

  8. Predicting Solar Flares by Data Assimilation in Avalanche Models. I. Model Design and Validation

    E-Print Network [OSTI]

    Eric Bélanger; Alain Vincent; Paul Charbonneau

    2007-08-14

    Data assimilation techniques, developed in the last two decades mainly for weather prediction, produce better forecasts by taking advantage of both theoretical/numerical models and real-time observations. In this paper, we explore the possibility of applying the data-assimilation techniques known as 4D-VAR to the prediction of solar flares. We do so in the context of a continuous version of the classical cellular-automaton-based self-organized critical avalanche models of solar flares introduced by Lu and Hamilton (Astrophys. J., 380, L89, 1991). Such models, although a priori far removed from the physics of magnetic reconnection and magneto-hydrodynamical evolution of coronal structures, nonetheless reproduce quite well the observed statistical distribution of flare characteristics. We report here on a large set of data assimilation runs on synthetic energy release time series. Our results indicate that, despite the unpredictable (and unobservable) stochastic nature of the driving/triggering mechanism within the avalanche model, 4D-VAR succeeds in producing optimal initial conditions that reproduce adequately the time series of energy released by avalanches/flares. This is an essential first step towards forecasting real flares.

  9. Constraints on the Bulk Lorentz Factors of GRB X-Ray Flares

    E-Print Network [OSTI]

    Yi, Shuang-Xi; Wang, Fa-Yin; Dai, Zi-Gao

    2015-01-01

    X-ray flares were discovered in the afterglow phase of gamma-ray bursts (GRBs) by the {\\em Swift} satellite a decade ago and known as a canonical component in GRB X-ray afterglows. In this paper, we constrain the Lorentz factors of GRB X-ray flares using two different methods. For the first method, we estimate the lower limit on the bulk Lorentz factor with the flare duration and jet break time. In the second method, the upper limit on the Lorentz factor is derived by assuming that the X-ray flare jet has undergone saturated acceleration. We also re-estimate the initial Lorentz factor with GRB afterglow onsets, and find the coefficient of the theoretical Lorentz factor is 1.67 rather than the commonly used 2 for interstellar medium (ISM) and 1.44 for the wind case. We find that the correlation between the limited Lorentz factor and the isotropic radiation energy of X-ray flares in the ISM case is more consistent with that of prompt emission than the wind case in a statistical sense. For a comparison, the lowe...

  10. IRIS Observations of the Mg II h & k Lines During a Solar Flare

    E-Print Network [OSTI]

    Kerr, Graham S; Qiu, Jiong; Fletcher, Lyndsay

    2015-01-01

    The bulk of the radiative output of a solar flare is emitted from the chromosphere, which produces enhancements in the optical and UV continuum, and in many lines, both optically thick and thin. We have, until very recently, lacked observations of two of the strongest of these lines: the Mg II h & k resonance lines. We present a detailed study of the response of these lines to a solar flare. The spatial and temporal behaviour of the integrated intensities, k/h line ratios, line of sight velocities, line widths and line asymmetries were investigated during an M class flare (SOL2014-02-13T01:40). Very intense, spatially localised energy input at the outer edge of the ribbon is observed, resulting in redshifts equivalent to velocities of ~15-26km/s, line broadenings, and a blue asymmetry in the most intense sources. The characteristic central reversal feature that is ubiquitous in quiet Sun observations is absent in flaring profiles, indicating that the source function increases with height during the flare....

  11. Observational Evidences of Electron-driven Evaporation in two Solar Flares

    E-Print Network [OSTI]

    Li, Dong; Zhang, Qingmin

    2015-01-01

    We have explored the relationship between hard X-ray (HXR) emissions and Doppler velocities caused by the chromospheric evaporation in two X1.6 class solar flares on 2014 September 10 and October 22, respectively. Both events display double ribbons and Interface Region Imaging Spectrograph (IRIS) slit is fixed on one of their ribbons from the flare onset. The explosive evaporations are detected in these two flares. The coronal line of Fe XXI 1354.09 A shows blue shifts, but chromospheric line of C I 1354.29 A shows red shifts during the impulsive phase. The chromospheric evaporation tends to appear at the front of flare ribbon. Both Fe XXI and C I display their Doppler velocities with a `increase-peak-decrease' pattern which is well related to the `rising-maximum- decay' phase of HXR emissions. Such anti-correlation between HXR emissions and Fe XXI Doppler shifts, and correlation with C I Doppler shifts indicate the electron-driven evaporation in these two flares.

  12. X-ray flares, neutrino cooled disks, and the dynamics of late accretion in GRB engines

    E-Print Network [OSTI]

    Davide Lazzati; Rosalba Perna; Mitchell C. Begelman

    2008-05-01

    We compute the average luminosity of X-ray flares as a function of time, for a sample of 10 long-duration gamma-ray burst afterglows. The mean luminosity, averaged over a timescale longer than the duration of the individual flares, declines as a power-law in time with index ~-1.5. We elaborate on the properties of the central engine that can produce such a decline. Assuming that the engine is an accreting compact object, and for a standard conversion factor between accretion rate and jet luminosity, the switch between a neutrino-cooled thin disk and a non-cooled thick disk takes place at the transition from the prompt to the flaring phase. We discuss the implications of this coincidence under different scenarios for the powering of the GRB outflow. We also show that the interaction of the outflow with the envelope of the progenitor star cannot produce flares out of a continuous relativistic flow, and conclude that it is the dynamics of the disk or the jet-launching mechanism that generates an intrinsically unsteady outflow on timescales much longer than the dynamical timescale of the system. This is consistent with the fact that X-ray flares are observed in short-duration GRBs as well as in long-duration ones.

  13. Are Heating Events in the Quiet Solar Corona Small Flares? - Multiwavelength Observations of Individual Events

    E-Print Network [OSTI]

    Sam Krucker; Arnold O. Benz

    1999-12-23

    Temporary enhancements of the coronal emission measure in a quiet region have been shown to constitute a significant energy input. Here some relatively large events are studied for simultaneous brightenings in transition region lines and in radio emission. Associated emissions are discussed and tested for characteristics known from full-sized impulsive flares in active regions. Heating events and flares are found to have many properties in common, including (i) associated polarized radio emission, which usually precedes the emission measure peak (Neupert effect) and sometimes has a non-thermal spectrum, and (ii) associated and often preceding peaks in O V and He I emission. On the other hand, heating events also differ from impulsive flares: (i) In half of the cases, their radio emission at centimeter waves shows a spectrum consistent with thermal radiation,(ii) the ratio of the gyro-synchrotron emission to the estimated thermal soft X-ray emission is smaller than in flares, and (iii) the associated emission in the O V transition region line shows red shifts and blue shifts, indicating upflows in the rise phase and downflows in the decay phase, respectively. Nevertheless, the differences seem to be mainly quantitative, and the analyzed heating events with thermal energies around 10^26 erg may in principle be considered as microflares or large nanoflares, thus small versions of regular flares.

  14. Correlation of hard X-ray and white light emission in solar flares

    E-Print Network [OSTI]

    Kuhar, Matej; Oliveros, Juan Carlos Martínez; Battaglia, Marina; Kleint, Lucia; Casadei, Diego; Hudson, Hugh S

    2015-01-01

    A statistical study of the correlation between hard X-ray and white light emission in solar flares is performed in order to search for a link between flare-accelerated electrons and white light formation. We analyze 43 flares spanning GOES classes M and X using observations from RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) and HMI (Helioseismic and Magnetic Imager). We calculate X-ray fluxes at 30 keV and white light fluxes at 6173 \\r{A} summed over the hard X-ray flare ribbons with an integration time of 45 seconds around the peak hard-X ray time. We find a good correlation between hard X-ray fluxes and excess white light fluxes, with a highest correlation coefficient of 0.68 for photons with energy of 30 keV. Assuming the thick target model, a similar correlation is found between the deposited power by flare-accelerated electrons and the white light fluxes. The correlation coefficient is found to be largest for energy deposition by electrons above ~50 keV. At higher electron energies the co...

  15. Loan Loss Reserve Fund Impacts on Standard Residential Underwriting Guidelines

    Broader source: Energy.gov [DOE]

    State and local governments can use loan loss reserve (LLR) funds to persuade lenders to offer more flexible terms during the underwriting process. The availability of an LLR can have the following...

  16. NEUTRON MONITOR DATA ON THE 15 JUNE 1991 FLARE: NEUTRONS AS A TEST FOR PROTON ACCELERATION SCENARIO

    E-Print Network [OSTI]

    Usoskin, Ilya G.

    NEUTRON MONITOR DATA ON THE 15 JUNE 1991 FLARE: NEUTRONS AS A TEST FOR PROTON ACCELERATION SCENARIO.J.TANSKANEN University of Oulu, SF-90570, Oulu, Finland ABSTRACT. Response of A1ma-Ata neuuon monitor for solar neutrons of proton acceleration during the flare. The analysis of neutron monitor is an evidence in favour

  17. PROPERTIES OF FAST SUBMILLIMETER TIME STRUCTURES DURING A LARGE SOLAR FLARE Jean-Pierre Raulin, Pierre Kaufmann,1

    E-Print Network [OSTI]

    Giménez de Castro, Guillermo Carlos

    et al. 1994). It has long been recognized that microwave solar bursts are composed of variationsPROPERTIES OF FAST SUBMILLIMETER TIME STRUCTURES DURING A LARGE SOLAR FLARE Jean-Pierre Raulin of the strongest solar radio flares of solar cycle 23. Emission was obtained by the Solar Submillimeter

  18. MAGNETIC RECONNECTION: FROM 'OPEN' EXTREME-ULTRAVIOLET LOOPS TO CLOSED POST-FLARE ONES OBSERVED BY SDO

    SciTech Connect (OSTI)

    Zhang, Jun; Yang, Shuhong; Li, Ting; Zhang, Yuzong; Li, Leping [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Jiang, Chaowei, E-mail: zjun@nao.cas.cn, E-mail: shuhongyang@nao.cas.cn, E-mail: liting@nao.cas.cn, E-mail: yuzong@nao.cas.cn, E-mail: lepingli@nao.cas.cn, E-mail: cwjiang@spaceweather.ac.cn [SIGMA Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China)

    2013-10-10

    We employ Solar Dynamics Observatory observations and select three well-observed events including two flares and one extreme-ultraviolet (EUV) brightening. During the three events, the EUV loops clearly changed. One event was related to a major solar flare that took place on 2012 July 12 in active region NOAA AR 11520. 'Open' EUV loops rooted in a facula of the AR deflected to the post-flare loops and then merged with them while the flare ribbon approached the facula. Meanwhile, 'open' EUV loops rooted in a pore disappeared from top to bottom as the flare ribbon swept over the pore. The loop evolution was similar in the low-temperature channels (e.g., 171 Å) and the high-temperature channels (e.g., 94 Å). The coronal magnetic fields extrapolated from the photospheric vector magnetograms also show that the fields apparently 'open' prior to the flare become closed after it. The other two events were associated with a B1.1 flare on 2010 May 24 and an EUV brightening on 2013 January 03, respectively. During both of these two events, some 'open' loops either disappeared or darkened before the formation of new closed loops. We suggest that the observations reproduce the picture predicted by the standard magnetic reconnection model: 'open' magnetic fields become closed due to reconnection, manifesting as a transformation from 'open' EUV loops to closed post-flare ones.

  19. Turbulence in the Solar Atmosphere: Manifestations and Diagnostics via Solar Image Processing

    E-Print Network [OSTI]

    Manolis K. Georgoulis

    2005-11-15

    Intermittent magnetohydrodynamical turbulence is most likely at work in the magnetized solar atmosphere. As a result, an array of scaling and multi-scaling image-processing techniques can be used to measure the expected self-organization of solar magnetic fields. While these techniques advance our understanding of the physical system at work, it is unclear whether they can be used to predict solar eruptions, thus obtaining a practical significance for space weather. We address part of this problem by focusing on solar active regions and by investigating the usefulness of scaling and multi-scaling image-processing techniques in solar flare prediction. Since solar flares exhibit spatial and temporal intermittency, we suggest that they are the products of instabilities subject to a critical threshold in a turbulent magnetic configuration. The identification of this threshold in scaling and multi-scaling spectra would then contribute meaningfully to the prediction of solar flares. We find that the fractal dimension of solar magnetic fields and their multi-fractal spectrum of generalized correlation dimensions do not have significant predictive ability. The respective multi-fractal structure functions and their inertial-range scaling exponents, however, probably provide some statistical distinguishing features between flaring and non-flaring active regions. More importantly, the temporal evolution of the above scaling exponents in flaring active regions probably shows a distinct behavior starting a few hours prior to a flare and therefore this temporal behavior may be practically useful in flare prediction. The results of this study need to be validated by more comprehensive works over a large number of solar active regions.

  20. Evidence for Extended Acceleration of Solar-Flare Ions from 18-MeV Solar Neutrons Detected with the MESSENGER Neutron Spectrometer

    E-Print Network [OSTI]

    Nittler, Larry R.

    Evidence for Extended Acceleration of Solar-Flare Ions from 1­8-MeV Solar Neutrons Detected. These observations are the first detection of solar neutrons inside 1 AU. This flare contained multiple acceleration in solar flares. These ions are difficult to detect remotely if they do not have access to Page 2 of 33 #12

  1. Effect of the 14 July 2000 solar flare on Earth's FUV Thomas J. Immel, Stephen B. Mende, Harald U. Frey, and N. stgaard

    E-Print Network [OSTI]

    Mende, Stephen B.

    Effect of the 14 July 2000 solar flare on Earth's FUV emissions Thomas J. Immel, Stephen B. Mende; revised 18 September 2002; accepted 4 February 2003; published 15 April 2003. [1] An X-class solar flare) confirm the close correlation between solar EUV and terrestrial FUV emissions. A comparison of the flare

  2. Particle dynamics in a non-flaring solar active region model

    E-Print Network [OSTI]

    Threlfall, J; Neukirch, T; Parnell, C E

    2015-01-01

    The aim of this work is to investigate and characterise particle behaviour in a (observationally-driven) 3D MHD model of the solar atmosphere above a slowly evolving, non-flaring active region. We use a relativistic guiding-centre particle code to investigate particle acceleration in a single snapshot of the 3D MHD simulation. Despite the lack of flare-like behaviour in the active region, direct acceleration of electrons and protons to non-thermal energies ($\\lesssim420$MeV) was found, yielding spectra with high-energy tails which conform to a power law. Examples of particle dynamics, including particle trapping caused by local electric rather than magnetic field effects, are observed and discussed, together with implications for future experiments which simulate non-flaring active region heating and reconnection.

  3. Clusters of small eruptive flares produced by magnetic reconnection in the sun

    E-Print Network [OSTI]

    Archontis, V

    2015-01-01

    We report on the formation of small solar flares produced by patchy magnetic reconnection between interacting magnetic loops. A three-dimensional (3D) magnetohydrodynamic (MHD) numerical experiment was performed, where a uniform magnetic flux sheet was injected into a fully developed convective layer. The gradual emergence of the field into the solar atmosphere results in a network of magnetic loops, which interact dynamically forming current layers at their interfaces. The formation and ejection of plasmoids out of the current layers leads to patchy reconnection and the spontaneous formation of several small (size ? 1-2Mm) flares. We find that these flares are short-lived (30 s - 3 min) bursts of energy in the range O(10^25 - 10^27) ergs, which is basically the nanoflare-microflare range. Their persistent formation and co-operative action and evolution leads to recurrent emission of fast EUV/X-ray jets and considerable plasma heating in the active corona.

  4. Observation and numerical modeling of chromospheric evaporation during the impulsive phase of a solar flare

    E-Print Network [OSTI]

    Imada, Shinsuke; Watanabe, Tetsuya

    2015-01-01

    We have studied the chromospheric evaporation flow during the impulsive phase of the flare by using the Hinode/EIS observation and 1D hydrodynamic numerical simulation coupled to the time-dependent ionization. The observation clearly shows that the strong redshift can be observed at the base of the flaring loop only during the impulsive phase. We performed two different numerical simulations to reproduce the strong downflows in FeXII and FeXV during the impulsive phase. By changing the thermal conduction coefficient, we carried out the numerical calculation of chromospheric evaporation in the thermal conduction dominant regime (conductivity coefficient kappa0 = classical value) and the enthalpy flux dominant regime (kappa0 = 0.1 x classical value). The chromospheric evaporation calculation in the enthalpy flux dominant regime could reproduce the strong redshift at the base of the flare during the impulsive phase. This result might indicate that the thermal conduction can be strongly suppressed in some cases o...

  5. CLUSTERS OF SMALL ERUPTIVE FLARES PRODUCED BY MAGNETIC RECONNECTION IN THE SUN

    SciTech Connect (OSTI)

    Archontis, V.; Hansteen, V.

    2014-06-10

    We report on the formation of small solar flares produced by patchy magnetic reconnection between interacting magnetic loops. A three-dimensional (3D) magnetohydrodynamic (MHD) numerical experiment was performed, where a uniform magnetic flux sheet was injected into a fully developed convective layer. The gradual emergence of the field into the solar atmosphere results in a network of magnetic loops, which interact dynamically forming current layers at their interfaces. The formation and ejection of plasmoids out of the current layers leads to patchy reconnection and the spontaneous formation of several small (size ?1-2 Mm) flares. We find that these flares are short-lived (30 s–3 minutes) bursts of energy in the range O(10{sup 25}-10{sup 27}) erg, which is basically the nanoflare-microflare range. Their persistent formation and co-operative action and evolution leads to recurrent emission of fast EUV/X-ray jets and considerable plasma heating in the active corona.

  6. Gamma-ray flares in the Crab Nebula: A case of relativistic reconnection?

    SciTech Connect (OSTI)

    Cerutti, B.; Werner, G. R. Uzdensky, D. A.; Begelman, M. C.

    2014-05-15

    The Crab Nebula was formed after the collapse of a massive star about a thousand years ago, leaving behind a pulsar that inflates a bubble of ultra-relativistic electron-positron pairs permeated with magnetic field. The observation of brief but bright flares of energetic gamma rays suggests that pairs are accelerated to PeV energies within a few days; such rapid acceleration cannot be driven by shocks. Here, it is argued that the flares may be the smoking gun of magnetic dissipation in the Nebula. Using 2D and 3D particle-in-cell simulations, it is shown that the observations are consistent with relativistic magnetic reconnection, where pairs are subject to strong radiative cooling. The Crab flares may highlight the importance of relativistic magnetic reconnection in astrophysical sources.

  7. Gas Water Heater Energy Losses

    E-Print Network [OSTI]

    Biermayer, Peter

    2012-01-01

    including delivered hot water and energy losses. Waterand 17% if hot water energy is included. INTRODUCTION Thedrawn, determines the hot water energy output. The current

  8. MAGNETIC ENERGY PARTITION BETWEEN THE CORONAL MASS EJECTION AND FLARE FROM AR 11283

    SciTech Connect (OSTI)

    Feng, L.; Li, Y. P.; Gan, W. Q.; Wiegelmann, T.; Inhester, B.; Su, Y.; Sun, X. D.

    2013-03-01

    On 2011 September 6, an X-class flare and a halo coronal mass ejection (CME) were observed from Earth erupting from the same active region AR 11283. The magnetic energy partition between them has been investigated. SDO/HMI vector magnetograms were used to obtain the coronal magnetic field using the nonlinear force-free field (NLFFF) extrapolation method. The free magnetic energies before and after the flare were calculated to estimate the released energy available to power the flare and the CME. For the flare energetics, thermal and nonthermal energies were derived using the RHESSI and GOES data. To obtain the radiative output, SDO/EVE data in the 0.1-37 nm waveband were utilized. We have reconstructed the three-dimensional (3D) periphery of the CME from the coronagraph images observed by STEREO-A, B, and SOHO. The mass calculations were then based on a more precise Thomson-scattering geometry. The subsequent estimate of the kinetic and potential energies of the CME took advantage of the more accurate mass, and the height and speed in a 3D frame. The released free magnetic energy resulting from the NLFFF model is about 6.4 Multiplication-Sign 10{sup 31} erg, which has a possible upper limit of 1.8 Multiplication-Sign 10{sup 32} erg. The thermal and nonthermal energies are lower than the radiative output of 2.2 Multiplication-Sign 10{sup 31} erg from SDO/EVE for this event. The total radiation covering the whole solar spectrum is probably a few times larger. The sum of the kinetic and potential energy of the CME could go up to 6.5 Multiplication-Sign 10{sup 31} erg. Therefore, the free energy is able to power the flare and the CME in AR 11283. Within the uncertainty, the flare and the CME may consume a similar amount of free energy.

  9. Search for correlations between solar flares and decay rate of radioactive nuclei

    E-Print Network [OSTI]

    E. Bellotti; C. Broggini; G. Di Carlo; M. Laubenstein; R. Menegazzo

    2013-02-05

    The deacay rate of three different radioactive sources 40K, 137Cs and natTh has been measured with NaI and Ge detectors. Data have been analyzed to search for possible variations in coincidence with the two strongest solar flares of the years 2011 and 2012. No significant deviations from standard expectation have been observed, with a few 10-4 sensitivity. As a consequence, we could not find any effect like that recently reported by Jenkins and Fischbach: a few per mil decrease in the decay rate of 54Mn during solar flares in December 2006.

  10. Plastic damping of Alfv\\'en waves in magnetar flares and delayed afterglow emission

    E-Print Network [OSTI]

    Li, Xinyu

    2015-01-01

    Magnetar flares generate Alfv\\'en waves bouncing in the closed magnetosphere with energy up to $\\sim 10^{46}$ erg. We show that on a 10-ms timescale the waves are transmitted into the star and form a compressed packet of high energy density. This packet strongly shears the stellar crust and initiates a plastic flow, heating the crust and melting it hundreds of meters below the surface. A fraction of the deposited plastic heat is eventually conducted to the stellar surface, contributing to the surface afterglow months to years after the flare. A large fraction of heat is lost to neutrino emission or conducted into the core of the neutron star.

  11. Lag-luminosity relation in gamma-ray burst X-ray flares

    SciTech Connect (OSTI)

    Margutti, R.

    2010-10-15

    In strict analogy to prompt pulses, X-ray flares observed by Swift-XRT in long Gamma-Ray Bursts define a lag-luminosity relation: L{sub p,iso}{sup 0.3-10} k{sup eV} {infinity}t{sub lag}{sup -0.95{+-}0.23}. The lag-luminosity is proven to be a fundamental law extending {approx}5 decades in time and {approx}5 in energy. This is direct evidence that GRB X-ray flares and prompt gamma-ray pulses are produced by the same mechanism.

  12. 1 Hz FLARING IN SAX J1808.4-3658: FLOW INSTABILITIES NEAR THE PROPELLER STAGE

    SciTech Connect (OSTI)

    Patruno, Alessandro; Watts, Anna; Klein Wolt, Marc; Wijnands, Rudy; Van der Klis, Michiel

    2009-12-20

    We present a simultaneous periodic and aperiodic timing study of the accreting millisecond X-ray pulsar SAX J1808.4-3658. We analyze five outbursts of the source and for the first time provide a full and systematic investigation of the enigmatic phenomenon of the 1 Hz flares observed during the final stages of some of the outbursts. We show that links between pulsations and 1 Hz flares might exist, and suggest that they are related with hydrodynamic disk instabilities that are triggered close to the disk-magnetosphere boundary layer when the system is entering the propeller regime.

  13. Naked Stony Corals: Skeleton Loss in Scleractinia

    E-Print Network [OSTI]

    Medina, Monica; Collins, Allen G.; Takaoka, Tori L.; Kuehl, Jennifer; Boore, Jeffrey L.

    2005-01-01

    LBNL-59177 Naked Stony Corals: Skeleton Loss in ScleractiniaKuehl, Jeffrey L. Boore Naked Stony Corals: Skeleton Loss in

  14. High-cadence and high-resolution H? imaging spectroscopy of a circular flare's remote ribbon with IBIS

    SciTech Connect (OSTI)

    Deng, Na; Jing, Ju; Chen, Xin; Liu, Chang; Xu, Yan; Wang, Haimin [Space Weather Research Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Tritschler, Alexandra; Reardon, Kevin [National Solar Observatory, Sacramento Peak, Sunspot, NM 88349-0062 (United States); Denker, Carsten, E-mail: na.deng@njit.edu [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany)

    2013-06-01

    We present an unprecedented high-resolution H? imaging spectroscopic observation of a C4.1 flare taken with the Interferometric Bidimensional Spectrometer (IBIS) in conjunction with the adaptive optics system at the 76 cm Dunn Solar Telescope on 2011 October 22 in the active region NOAA 11324. Such a two-dimensional spectroscopic observation covering the entire evolution of a flare ribbon with high spatial (0.''1 pixel{sup –1} image scale), cadence (4.8 s), and spectral (0.1 Å step size) resolution is rarely reported. The flare consists of a main circular ribbon that occurred in a parasitic magnetic configuration and a remote ribbon that was observed by the IBIS. Such a circular-ribbon flare with a remote brightening is predicted in three-dimensional fan-spine reconnection but so far has been rarely studied. During the flare impulsive phase, we define 'core' and 'halo' structures in the observed ribbon based on IBIS narrowband images in the H? line wing and line center. Examining the H? emission spectra averaged in the flare core and halo areas, we find that only those from the flare cores show typical nonthermal electron beam heating characteristics that have been revealed by previous theoretical simulations and observations of flaring H? line profiles. These characteristics include broad and centrally reversed emission spectra, excess emission in the red wing with regard to the blue wing (i.e., red asymmetry), and redshifted bisectors of the emission spectra. We also observe rather quick timescales for the heating (?30 s) and cooling (?14-33 s) in the flare core locations. Therefore, we suggest that the flare cores revealed by IBIS track the sites of electron beam precipitation with exceptional spatial and temporal resolution. The flare cores show two-stage motion (a parallel motion along the ribbon followed by an expansion motion perpendicular to the ribbon) during the two impulsive phases of the flare. Some cores jump quickly (30 km s{sup –1}) between discrete magnetic elements implying reconnection involving different flux tubes. We observe a very high temporal correlation (? 0.9) between the integrated H? and hard X-rays (HXR) emission during the flare impulsive phase. A short time delay (4.6 s) is also found in the H? emission spikes relative to HXR bursts. The ionization timescale of the cool chromosphere and the extra time taken for the electrons to travel to the remote ribbon site may contribute to this delay.

  15. The shock reprocessing model of electron acceleration in impulsive solar flares

    E-Print Network [OSTI]

    Selkowitz, R; Selkowitz, Robert; Blackman, Eric G.

    2005-01-01

    We propose a new two-stage model for acceleration of electrons in solar flares. In the first stage, electrons are accelerated stochastically in a post-reconnection turbulent downflow. The second stage is the reprocessing of a subset of these electrons as they pass through a weakly compressive fast shock above the apex of the closed flare loop on their way to the chromosphere. We call this the "shock reprocessing" model. The model reproduces the energy dependent arrival time delays observed for both the pulsed and smooth components of impulsive solar flare x-rays with physically reasonable parameters for the downflow region. The model also predicts an emission site above the loop-top, as seen in the Masuda flare. The loop-top source distinguishes the shock reprocessing model from previous models. The model makes testable predictions for the energy dependence of footpoint pulse strengths and the location and spectrum of the loop-top emission, and can account for the observed soft-hard-soft trend in the spectral...

  16. Observations of Solar Flare Doppler Shift Oscillations with the Bragg Crystal Spectrometer on Yohkoh

    E-Print Network [OSTI]

    John T. Mariska

    2005-01-06

    Oscillations in solar coronal loops appear to be a common phenomenon. Transverse and longitudinal oscillations have been observed with both the Transition Region and Coronal Explorer and Extreme Ultraviolet Imaging Telescope imaging experiments. Damped Doppler shift oscillations have been observed in emission lines from ions formed at flare temperatures with the Solar Ultraviolet Measurements of Emitted Radiation Spectrometer. These observations provide valuable diagnostic information on coronal conditions and may help refine our understanding of coronal heating mechanisms. I have initiated a study of the time dependence of Doppler shifts measured during flares with the Bragg Crystal Spectrometer (BCS) on Yohkoh. This Letter reports the detection of oscillatory behavior in Doppler shifts measured as a function of time in the emission lines of S XV and Ca XIX. For some flares, both lines exhibit damped Doppler shift oscillations with amplitudes of a few km/s and periods and decay times of a few minutes. The observations appear to be consistent with transverse oscillations. Because the BCS observed continuously for almost an entire solar cycle, it provides numerous flare data sets, which should permit an excellent characterization of the average properties of the oscillations.

  17. The Sun as an X-ray Star: III. Flares F. Reale, G. Peres

    E-Print Network [OSTI]

    distribution vs. temperature and its evolution during some selected solar ares, representative of the wideThe Sun as an X-ray Star: III. Flares F. Reale, G. Peres Dip. di Scienze Fisiche & Astronomiche class C5.8) to very intense ones (X9) are selected as representative of the aring Sun. The emission

  18. CHARACTERISTIC SIZE OF FLARE KERNELS IN THE VISIBLE AND NEAR-INFRARED CONTINUA

    SciTech Connect (OSTI)

    Xu, Yan; Jing, Ju; Wang, Haimin [Space Weather Research Lab, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Blvd, Newark, NJ 07102-1982 (United States); Cao, Wenda, E-mail: yx2@njit.edu [Big Bear Solar Observatory, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Blvd, Newark, NJ 07102-1982 (United States)

    2012-05-01

    In this Letter, we present a new approach to estimate the formation height of visible and near-infrared emission of an X10 flare. The sizes of flare emission cores in three wavelengths are accurately measured during the peak of the flare. The source size is the largest in the G band at 4308 A and shrinks toward longer wavelengths, namely the green continuum at 5200 A and NIR at 15600 A, where the emission is believed to originate from the deeper atmosphere. This size-wavelength variation is likely explained by the direct heating model as electrons need to move along converging field lines from the corona to the photosphere. Therefore, one can observe the smallest source, which in our case is 0.''65 {+-} 0.''02 in the bottom layer (represented by NIR), and observe relatively larger kernels in upper layers of 1.''03 {+-} 0.''14 and 1.''96 {+-} 0.''27, using the green continuum and G band, respectively. We then compare the source sizes with a simple magnetic geometry to derive the formation height of the white-light sources and magnetic pressure in different layers inside the flare loop.

  19. The Temporal Behaviour of Lyman-alpha Emission During Solar Flares From SDO/EVE

    E-Print Network [OSTI]

    Milligan, Ryan O

    2015-01-01

    Despite being the most prominent emission line in the solar spectrum, there has been a notable lack of studies devoted to variations in Lyman-alpha (Ly$\\alpha$) emission during solar flares in recent years. The few examples that do exist, however, have shown Ly$\\alpha$ emission to be a substantial radiator of the total energy budget of solar flares (on the order of 10%). It is also a known driver of fluctuations in earth's ionosphere. The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory now provides broadband, photometric Ly$\\alpha$ data at 10 s cadence, and has observed scores of solar flares in the 5 years since it was launched. However, the time profiles appear to display a rise time of tens of minutes around the time of the flare onset. This is in stark contrast to the rapid, impulsive increase observed in other intrinsically chromospheric features (H$\\alpha$, Ly$\\beta$, LyC, C III, etc.). Furthermore, the Ly$\\alpha$ emission peaks around the time of the peak of thermal soft X-ray e...

  20. THE 5 GHz ARECIBO SEARCH FOR RADIO FLARES FROM ULTRACOOL DWARFS

    SciTech Connect (OSTI)

    Route, Matthew; Wolszczan, Alexander E-mail: alex@astro.psu.edu

    2013-08-10

    We present the results of a 4.75 GHz survey of 33 brown dwarfs and one young exoplanetary system for flaring radio emission, conducted with the 305 m Arecibo radio telescope. The goal of this program was to detect and characterize the magnetic fields of objects cooler than spectral type L3.5, the coolest brown dwarf detected prior to our survey. We have also attempted to detect flaring radio emission from the HR 8799 planetary system, guided by theoretical work indicating that hot, massive exoplanets may have strong magnetic fields capable of generating radio emission at GHz frequencies. We have detected and confirmed radio flares from the T6.5 dwarf 2MASS J10475385+2124234. This detection dramatically extends the temperature range over which brown dwarfs appear to be at least sporadic radio-emitters, from 1900 K (L3.5) down to 900 K (T6.5). It also demonstrates that the utility of radio detection as a unique tool to study the magnetic fields of substellar objects extends to the coolest dwarfs, and, plausibly to hot, massive exoplanets. We have also identified a single, 3.6{sigma} flare from the L1 dwarf, 2MASS J1439284+192915. This detection is tentative and requires confirmation by additional monitoring observations.

  1. NO FLARES FROM GAMMA-RAY BURST AFTERGLOW BLAST WAVES ENCOUNTERING SUDDEN CIRCUMBURST DENSITY CHANGE

    SciTech Connect (OSTI)

    Gat, Ilana; Van Eerten, Hendrik; MacFadyen, Andrew [Center for Cosmology and Particle Physics, Physics Department, New York University, New York, NY 10003 (United States)

    2013-08-10

    Afterglows of gamma-ray bursts are observed to produce light curves with the flux following power-law evolution in time. However, recent observations reveal bright flares at times on the order of minutes to days. One proposed explanation for these flares is the interaction of a relativistic blast wave with a circumburst density transition. In this paper, we model this type of interaction computationally in one and two dimensions, using a relativistic hydrodynamics code with adaptive mesh refinement called RAM, and analytically in one dimension. We simulate a blast wave traveling in a stellar wind environment that encounters a sudden change in density, followed by a homogeneous medium, and compute the observed radiation using a synchrotron model. We show that flares are not observable for an encounter with a sudden density increase, such as a wind termination shock, nor for an encounter with a sudden density decrease. Furthermore, by extending our analysis to two dimensions, we are able to resolve the spreading, collimation, and edge effects of the blast wave as it encounters the change in circumburst medium. In all cases considered in this paper, we find that a flare will not be observed for any of the density changes studied.

  2. Temporal evolution of multiple evaporating ribbon sources in a solar flare

    E-Print Network [OSTI]

    Graham, D R

    2015-01-01

    We present new results from the Interface Region Imaging Spectrograph showing the dynamic evolution of chromospheric evaporation and condensation in a flare ribbon, with the highest temporal and spatial resolution to date. IRIS observed the entire impulsive phase of the X-class flare SOL2014-09-10T17:45 using a 9.4 second cadence `sit-and-stare' mode. As the ribbon brightened successively at new positions along the slit, a unique impulsive phase evolution was observed for many tens of individual pixels in both coronal and chromospheric lines. Each activation of a new footpoint displays the same initial coronal up-flows of up to ~300 km/s, and chromospheric downflows up to 40 km/s. Although the coronal flows can be delayed by over 1 minute with respect to those in the chromosphere, the temporal evolution of flows is strikingly similar between all pixels, and consistent with predictions from hydrodynamic flare models. Given the large sample of independent footpoints, we conclude that each flaring pixel can be c...

  3. A unified view of coronal loop contraction and oscillation in flares

    E-Print Network [OSTI]

    Russell, Alexander J B; Fletcher, Lyndsay

    2015-01-01

    Context: Transverse loop oscillations and loop contractions are commonly associated with solar flares, but the two types of motion have traditionally been regarded as separate phenomena. Aims: We present an observation of coronal loops contracting and oscillating following onset of a flare. We aim to explain why both behaviours are seen together and why only some of the loops oscillate. Methods: A time sequence of SDO/AIA 171 \\r{A} images is analysed to identify positions of coronal loops following the onset of M6.4 flare SOL2012-03-09T03:53. We focus on five loops in particular, all of which contract during the flare, with three of them oscillating as well. A simple model is then developed for contraction and oscillation of a coronal loop. Results: We propose that coronal loop contractions and oscillations can occur in a single response to removal of magnetic energy from the corona. Our model reproduces the various types of loop motion observed and explains why the highest loops oscillate during their contra...

  4. Hard X-ray Emission During Flares and Photospheric Field Changes

    E-Print Network [OSTI]

    Burtseva, O; Petrie, G J D; Pevtsov, A A

    2015-01-01

    We study the correlation between abrupt permanent changes of magnetic field during X-class flares observed by the GONG and HMI instruments, and the hard X-ray (HXR) emission observed by RHESSI, to relate the photospheric field changes to the coronal restructuring and investigate the origin of the field changes. We find that spatially the early RHESSI emission corresponds well to locations of the strong field changes. The field changes occur predominantly in the regions of strong magnetic field near the polarity inversion line (PIL). The later RHESSI emission does not correspond to significant field changes as the flare footpoints are moving away from the PIL. Most of the field changes start before or around the start time of the detectable HXR signal, and they end at about the same time or later than the detectable HXR flare emission. Some of the field changes propagate with speed close to that of the HXR footpoint at a later phase of the flare. The propagation of the field changes often takes place after the...

  5. Hard X-ray and ultraviolet emission during the 2011 June 7 solar flare

    E-Print Network [OSTI]

    Inglis, Andrew R

    2013-01-01

    The relationship between X-ray and UV emission during flares, particularly in the context of quasi-periodic pulsations, remains unclear. To address this, we study the X-ray and UV emission during the eruptive flare of 2011 June 7 utilising X-ray imaging from RHESSI and UV 1700A imaging from SDO/AIA. This event is associated with synchronous quasi-periodic pulsations in both the X-ray and UV emission, as well as substantial motion of the hard X-ray footpoints. The motion of the footpoint associated with the left-hand flare ribbon is shown to reverse direction along the flare ribbons on at least two occasions. Over the same time interval, the footpoints also gradually move apart at v ~ 12 km/s. This is consistent with the measured plane-of-sky thermal X-ray source outward velocity of ~ 14 km/s, and matches the gradual outward expansion of the UV ribbons. However, there is no associated short-timescale motion of the UV bright regions. We find that the locations of the brightest X-ray and UV regions are different...

  6. On the Relation between Filament Eruptions, Flares, and Coronal Mass Ejections

    E-Print Network [OSTI]

    On the Relation between Filament Eruptions, Flares, and Coronal Mass Ejections Ju Jing, Vasyl B a statistical study of 106 filament eruptions, which were automat- ically detected by a pattern recognition and Large Angle and Spectrometric Corona- graph (LASCO) data to determine the relationship between filament

  7. A Circular-ribbon Solar Flare Following an Asymmetric Filament Eruption

    E-Print Network [OSTI]

    Liu, Chang; Liu, Rui; Lee, Jeongwoo; Pariat, Etienne; Wiegelmann, Thomas; Liu, Yang; Kleint, Lucia; Wang, Haimin

    2015-01-01

    The dynamic properties of flare ribbons and the often associated filament eruptions can provide crucial information on the flaring coronal magnetic field. This Letter analyzes the GOES-class X1.0 flare on 2014 March 29 (SOL2014-03-29T17:48), in which we found an asymmetric eruption of a sigmoidal filament and an ensuing circular flare ribbon. Initially both EUV images and a preflare nonlinear force-free field model show that the filament is embedded in magnetic fields with a fan-spine-like structure. In the first phase, which is defined by a weak but still increasing X-ray emission, the western portion of the sigmoidal filament arches upward and then remains quasi-static for about five minutes. The western fan-like and the outer spine-like fields display an ascending motion, and several associated ribbons begin to brighten. Also found is a bright EUV flow that streams down along the eastern fan-like field. In the second phase that includes the main peak of hard X-ray (HXR) emission, the filament erupts, leavi...

  8. CELLULAR AUTOMATA MODELS AND MHD APPROACH IN THE CONTEXT OF SOLAR FLARES 1

    E-Print Network [OSTI]

    Anastasiadis, Anastasios

    CELLULAR AUTOMATA MODELS AND MHD APPROACH IN THE CONTEXT OF SOLAR FLARES 1 Anastasios Anastasiadis anastasi@space.noa.gr Abstract: We address in detail the cellular automaton approach, developed be used. These types of mathematical tools are the Automata and the Cellular Automata (CA). The advantage

  9. PRODUCTIVITY OF SOLAR FLARES AND MAGNETIC HELICITY INJECTION IN ACTIVE REGIONS

    E-Print Network [OSTI]

    effect on cell phones and the global positioning system and heat up the terrestrial atmosphere within). Solar flares produce high energy particles, radiation, and erupting magnetic structures that are related to geomagnetic storms. Their strong electro- magnetic radiations from radio waves to gamma-rays have direct

  10. GRB 051103 and GRB 070201 as Giant Flares from SGRs in Nearby Galaxies

    E-Print Network [OSTI]

    California at Berkeley, University of

    -7450, USA ^Max-Plank-Institutfiir extraterrestrische Physik, D-85741 Garching, Germany Abstract. The Konus-Wind, 12]. The energy of the initial pulse of the giant flare from SGR 1806-20 was found of '-^ 2 x 10 of commonly accepted observational GF criteria (i.e. short duration, single pulse event with hard energy

  11. The use of electron maps to constrain some physical properties of solar flares

    E-Print Network [OSTI]

    Piana, Michele

    astrophysical phenomenon into observable data. In the case of the NASA Reuven Ramaty High Energy Solar Energy Solar Spectroscopic Imager (RHESSI) is a set of Fourier components of the X-ray radiation samThe use of electron maps to constrain some physical properties of solar flares A. M. Massone1 and M

  12. Systematic Microwave Source Motions along Flare-arcade Observed by Nobeyama Radioheliograph and AIA/SDO

    E-Print Network [OSTI]

    Kim, Sujin; Masuda, Satoshi

    2013-01-01

    We found systematic microwave source motions along a flare-arcade using Nobeyama Radioheliograph (NoRH) 17 GHz images. The motions were associated with a X-class disk flare which occurred on 15th February 2011. For this study, we also used EUV images from Atmospheric Imaging Assembly (AIA) and magnetograms from Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory, and multi-channel microwave data from Nobeyama Radiopolarimeters (NoRP) and Korean Solar Radio Burst Locator (KSRBL). We traced centroids of the microwave source observed by NoRH 17 GHz during the flare and found two episodes of the motion with several facts: 1) The microwave source moved systematically along the flare-arcade, which was observed by the AIA 94 A in a direction parallel to the neutral line. 2) The period of each episode was 5 min and 14 min, respectively. 3) Estimated parallel speed was 34 km/s for the first episode and 22 km/s for the second episode. The spectral slope of microwave flux above 10 GHz obtained by N...

  13. A Multiwavelength Study of Three Solar Flares M. R. Kundu, A. Nindos 1 , S. M. White

    E-Print Network [OSTI]

    White, Stephen

    of the are phenomenon. Microwave emission from solar ares can provide important diagnostics of acceleration pro- cesses 1998) that the basic emission mechanism of solar microwave bursts is gyrosynchrotron from mildlyA Multiwavelength Study of Three Solar Flares M. R. Kundu, A. Nindos 1 , S. M. White Astronomy

  14. Testing Automated Solar Flare Forecasting With 13 Years of MDI Synoptic Magnetograms

    E-Print Network [OSTI]

    Hoeksema, Todd

    becomes more technologically dependent on complex global systems, the potential risk posedTesting Automated Solar Flare Forecasting With 13 Years of MDI Synoptic Magnetograms J.P. Mason1 is statistically associated with changes in several characteris- tics of the line-of-sight magnetic field in solar

  15. SOLAR FLARE PREDICTION USING SDO/HMI VECTOR MAGNETIC FIELD DATA WITH A MACHINE-LEARNING ALGORITHM

    SciTech Connect (OSTI)

    Bobra, M. G.; Couvidat, S.

    2015-01-10

    We attempt to forecast M- and X-class solar flares using a machine-learning algorithm, called support vector machine (SVM), and four years of data from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager, the first instrument to continuously map the full-disk photospheric vector magnetic field from space. Most flare forecasting efforts described in the literature use either line-of-sight magnetograms or a relatively small number of ground-based vector magnetograms. This is the first time a large data set of vector magnetograms has been used to forecast solar flares. We build a catalog of flaring and non-flaring active regions sampled from a database of 2071 active regions, comprised of 1.5 million active region patches of vector magnetic field data, and characterize each active region by 25 parameters. We then train and test the machine-learning algorithm and we estimate its performances using forecast verification metrics with an emphasis on the true skill statistic (TSS). We obtain relatively high TSS scores and overall predictive abilities. We surmise that this is partly due to fine-tuning the SVM for this purpose and also to an advantageous set of features that can only be calculated from vector magnetic field data. We also apply a feature selection algorithm to determine which of our 25 features are useful for discriminating between flaring and non-flaring active regions and conclude that only a handful are needed for good predictive abilities.

  16. IMPULSIVE ACCELERATION OF CORONAL MASS EJECTIONS. II. RELATION TO SOFT X-RAY FLARES AND FILAMENT ERUPTIONS

    SciTech Connect (OSTI)

    Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer, M.; Vrsnak, B.

    2012-08-10

    Using high time cadence images from the STEREO EUVI, COR1, and COR2 instruments, we derived detailed kinematics of the main acceleration stage for a sample of 95 coronal mass ejections (CMEs) in comparison with associated flares and filament eruptions. We found that CMEs associated with flares reveal on average significantly higher peak accelerations and lower acceleration phase durations, initiation heights, and heights, at which they reach their peak velocities and peak accelerations. This means that CMEs that are associated with flares are characterized by higher and more impulsive accelerations and originate from lower in the corona where the magnetic field is stronger. For CMEs that are associated with filament eruptions we found only for the CME peak acceleration significantly lower values than for events that were not associated with filament eruptions. The flare rise time was found to be positively correlated with the CME acceleration duration and negatively correlated with the CME peak acceleration. For the majority of the events the CME acceleration starts before the flare onset (for 75% of the events) and the CME acceleration ends after the soft X-ray (SXR) peak time (for 77% of the events). In {approx}60% of the events, the time difference between the peak time of the flare SXR flux derivative and the peak time of the CME acceleration is smaller than {+-}5 minutes, which hints at a feedback relationship between the CME acceleration and the energy release in the associated flare due to magnetic reconnection.

  17. Upper limits on the solar-neutron flux at the Yangbajing neutron monitor from BATSE-detected solar flares

    E-Print Network [OSTI]

    H. Tsuchiya; H. Miyasaka; E. Takahashi; S. Shimoda; Y. Yamada; I. Kondo; K. Makishima; F. Zhu; Y. Tan; H. Hu; Y. Tang; J. Zhang; H. Lu; X. Meng

    2007-03-16

    The purpose of this work is to search the Yangbajing neutron monitor data obtained between 1998 October and 2000 June for solar neutrons associated with solar flares. Using the onset times of 166 BATSE-detected flares with the GOES peak flux (1 -- 8 \\AA) higher than $1.0 \\times 10^{-5}$ $\\mathrm{Wm^{-2}}$, we prepare for each flare a light curve of the Yangbajing neutron monitor, spanning $\\pm$ 1.5 hours from the BATSE onset time. Based on the light curves, a systematic search for solar neutrons in energies above 100 MeV from the 166 flares was performed. No statistically significant signals due to solar neutrons were found in the present work. Therefore, we put upper limits on the $>$ 100 MeV solar-neutron flux for 18 events consisting of 2 X and 16 M class flares. The calculation assumed a power-law shaped neutron energy spectrum and three types of neutron emission profiles at the Sun. Compared with the other positive neutron detections associated with X-class flares, typical 95% confidence level upper limits for the two X-class flares are found to be comparable to the lowest and second lowest neutron fluxes at the top of the atmosphere.In addition, the upper limits for M-class flares scatter in the range of $10^{-2}$ to 1 neutrons $\\mathrm{cm^{-2}s^{-1}}$. This provides the first upper limits on the solar-neutron flux from M-class solar flares, using space observatories as well as ground-based neutron monitors.

  18. Beam Cooling with ionisation losses

    E-Print Network [OSTI]

    C. Rubbia; A. Ferrari; Y. Kadi; V. Vlachoudis

    2006-02-03

    A novel type of particle "cooling", called Ionization Cooling, is applicable to slow (v of the order of 0.1c) ions stored in a small ring. The many traversals through a thin foil enhance the nuclear reaction probability, in a steady configuration in which ionisation losses are recovered at each turn by a RF-cavity. For a uniform target "foil" the longitudinal momentum spread diverges exponentially since faster (slower) particles ionise less (more) than the average. In order to "cool" also longitudinally, a chromaticity has to be introduced with a wedge shaped "foil". Multiple scattering and straggling are then "cooled" in all three dimensions, with a method similar to the one of synchrotron cooling, but valid for low energy ions. Particles then stably circulate in the beam indefinitely, until they undergo for instance nuclear processes in the thin target foil. This new method is under consideration for the nuclear production of a few MeV/A ion beams. Simple reactions, for instance Li 7 + D Li 8 + p, are more favourably exploited with the heavier ion colliding against a gas-jet D2 target. Kinematics is generally very favourable, with emission angles in a narrow angular cone and a relatively concentrated outgoing energy spectrum which allows an efficient collection as a neutral gas in a tiny volume with a technology at high temperatures perfected at ISOLDE. It is however of a much more general applicability. The method appears capable of producing a "table top" storage ring with an accumulation rate in excess of 10**14 Li-8 radioactive ion/s for possible use for radioactive beams for physics studies (for example for beta-beams) or for therapy.

  19. On the origin of a sunquake during the 2014 March 29 X1 flare

    SciTech Connect (OSTI)

    Judge, Philip G. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States); Kleint, Lucia [Institute of 4D Technologies, University of Applied Sciences and Arts Northwestern Switzerland, 5210 Windisch (Switzerland); Donea, Alina [Center for Astrophysics, School of Mathematical Science, Monash University, Victoria 3800 (Australia); Dalda, Alberto Sainz [Stanford-Lockheed Institute for Space Research, Stanford University, HEPL, 466 Via Ortega, Stanford, CA 94305 (United States); Fletcher, Lyndsay, E-mail: judge@ucar.edu, E-mail: lucia.kleint@fhnw.ch, E-mail: alina.donea@monash.edu, E-mail: asdalda@stanford.edu, E-mail: lyndsay.fletcher@glasgow.ac.uk [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2014-12-01

    Helioseismic data from the Helioseismic Magnetic Imager instrument have revealed a sunquake associated with the X1 flare SOL2014-03-29T17:48 in active region NOAA 12017. We try to discover if acoustic-like impulses or actions of the Lorentz force caused the sunquake. We analyze spectropolarimetric data obtained with the Facility Infrared Spectrometer (FIRS) at the Dunn Solar Telescope (DST). Fortunately, the FIRS slit crossed the flare kernel close to the acoustic source during the impulsive phase. The infrared FIRS data remain unsaturated throughout the flare. Stokes profiles of lines of Si I 1082.7 nm and He I 1083.0 nm are analyzed. At the flare footpoint, the Si I 1082.7 nm core intensity increases by a factor of several, and the IR continuum increases by 4% ± 1%. Remarkably, the Si I core resembles the classical Ca II K line's self-reversed profile. With nLTE radiative models of H, C, Si, and Fe, these properties set the penetration depth of flare heating to 100 ± 100 km (i.e., photospheric layers). Estimates of the non-magnetic energy flux are at least a factor of two less than the sunquake energy flux. Milne-Eddington inversions of the Si I line show that the local magnetic energy changes are also too small to drive the acoustic pulse. Our work raises several questions. Have we missed the signature of downward energy propagation? Is it intermittent in time and/or non-local? Does the 1-2 s photospheric radiative damping time discount compressive modes?.

  20. HYDROGEN BALMER CONTINUUM IN SOLAR FLARES DETECTED BY THE INTERFACE REGION IMAGING SPECTROGRAPH (IRIS)

    SciTech Connect (OSTI)

    Heinzel, P. [Astronomical Institute, Academy of Sciences of the Czech Republic, Fri?ova 298, 25165 Ond?ejov (Czech Republic); Kleint, L., E-mail: pheinzel@asu.cas.cz [University of Applied Sciences and Arts Northwestern Switzerland, Bahnhofstrasse 6, 5210 Windisch (Switzerland)

    2014-10-20

    We present a novel observation of the white light flare (WLF) continuum, which was significantly enhanced during the X1 flare on 2014 March 29 (SOL2014-03-29T17:48). Data from the Interface Region Imaging Spectrograph (IRIS) in its near-UV channel show that at the peak of the continuum enhancement, the contrast at the quasi-continuum window above 2813 Å reached 100%-200% and can be even larger closer to Mg II lines. This is fully consistent with the hydrogen recombination Balmer-continuum emission, which follows an impulsive thermal and non-thermal ionization caused by the precipitation of electron beams through the chromosphere. However, a less probable photospheric continuum enhancement cannot be excluded. The light curves of the Balmer continuum have an impulsive character with a gradual fading, similar to those detected recently in the optical region on the Solar Optical Telescope on board Hinode. This observation represents a first Balmer-continuum detection from space far beyond the Balmer limit (3646 Å), eliminating seeing effects known to complicate the WLF detection. Moreover, we use a spectral window so far unexplored for flare studies, which provides the potential to study the Balmer continuum, as well as many metallic lines appearing in emission during flares. Combined with future ground-based observations of the continuum near the Balmer limit, we will be able to disentangle various scenarios of the WLF origin. IRIS observations also provide a critical quantitative measure of the energy radiated in the Balmer continuum, which constrains various models of the energy transport and deposit during flares.

  1. Abstract: During a flare, the increase in solar flux at X-ray and EUV wavelengths causes an enhancement in electron densities in planetary ionospheres. Although it is known that relative changes in electron density during a flare are greater for lower alt

    E-Print Network [OSTI]

    Withers, Paul

    Abstract: During a flare, the increase in solar flux at X-ray and EUV wavelengths causes in electron density during a solar flare, based on analysis of 12 Mars Global Surveyor (MGS) radio occultation electron density profiles which have been affected by solar flares. We find that solar zenith angle also

  2. Structure and Design a Finance Program with Loan Loss Reserve Funds

    Office of Energy Efficiency and Renewable Energy (EERE)

    The process for structuring and designing a finance program with a loan loss reserve (LLR) fund typically includes research and preparing a finance program design document.

  3. Iron loss calculation for synchronous reluctance machines

    SciTech Connect (OSTI)

    Leonardi, F.; Matsuo, T.; Lipo, T.A. [Univ. of Wisconsin, Madison, WI (United States)

    1995-12-31

    A numerical method for iron loss calculation is presented in this paper. The method is suitable for any synchronous and most dc machines, especially if the current waveforms are known a priori . This technique will be principally useful for high speed machines and in particular for the synchronous reluctance machines and in particular for the synchronous reluctance machine, where the iron losses are often an important issue. The calculation is based on Finite Element Analysis, which provides the flux density waveforms in the iron, and on the Fourier Analysis of these waveforms. Several Finite Element Simulations are necessary to obtain the induced voltage versus time waveforms. To reduce the post-processing time the majority of the elements of the model are grouped together to create super elements. Also the periodicity of the motor can be used to reduce the number of required simulations. The method is applied to the calculation of the iron losses of a synchronous reluctance generator, and a number of interesting results are discussed in the paper.

  4. Loop length and magnetic field estimates from oscillations detected during an X-ray flare on AT Mic

    E-Print Network [OSTI]

    U. Mitra-Kraev; L. K. Harra

    2004-10-27

    We analyse oscillations observed in the X-ray light curve of the late-type star AT Mic. The oscillations occurred during flare maximum. We interpret these oscillations as density perturbations in the flare loop. Applying various models derived for the Sun, the loop length and the magnetic field of the flare can be estimated. We find a period of 740 s, and that the models give similar results (within a factor of 2) for the loop length (~5.4e10 cm) and the magnetic field (~100 G). For the first time, an oscillation of a stellar X-ray flare has been observed and results thus obtained for otherwise unobservable physical parameters.

  5. Efficiency loss in resource allocation games

    E-Print Network [OSTI]

    Xu, Yunjian

    2012-01-01

    The overarching goals of this thesis are to quantify the efficiency loss due to market participant strategic behavior, and to design proper pricing mechanisms that reduce the efficiency loss. The concept of efficiency loss ...

  6. Fermilab experience of post-annealing losses in SRF niobium cavities due to furnace contamination and the ways to its mitigation: a pathway to processing simplification and quality factor improvement

    E-Print Network [OSTI]

    Grassellino, A; Crawford, A; Melnychuk, O; Rowe, A; Wong, M; Cooper, C; Sergatskov, D; Bice, D; Trenikhina, Y; Cooley, L D; Ginsburg, C; Kephart, R D

    2013-01-01

    We investigate the effect of high temperature treatments followed by only high-pressure water rinse (HPR) of superconducting radio frequency (SRF) niobium cavities. The objective is to provide a cost effective alternative to the typical cavity processing sequence, by eliminating the material removal step post furnace treatment while preserving or improving the RF performance. The studies have been conducted in the temperature range 800-1000C for different conditions of the starting substrate: large grain and fine grain, electro-polished (EP) and centrifugal barrel polished (CBP) to mirror finish. An interesting effect of the grain size on the performances is found. Cavity results and samples characterization show that furnace contaminants cause poor cavity performance, and a practical solution is found to prevent surface contamination. Extraordinary values of residual resistances ~ 1 nOhm and below are then consistently achieved for the contamination-free cavities. These results lead to a more cost-effective ...

  7. SUDDEN PHOTOSPHERIC MOTION AND SUNSPOT ROTATION ASSOCIATED WITH THE X2.2 FLARE ON 2011 FEBRUARY 15

    SciTech Connect (OSTI)

    Wang, Shuo; Liu, Chang; Deng, Na; Wang, Haimin

    2014-02-20

    The Helioseismic and Magnetic Imager provides 45 s cadence intensity images and 720 s cadence vector magnetograms. These unprecedented high-cadence and high-resolution data give us a unique opportunity to study the change of photospheric flows and sunspot rotations associated with flares. By using the differential affine velocity estimator method and the Fourier local correlation tracking method separately, we calculate velocity and vorticity of photospheric flows in the flaring NOAA AR 11158, and investigate their temporal evolution around the X2.2 flare on 2011 February 15. It is found that the shear flow around the flaring magnetic polarity inversion line exhibits a sudden decrease, and both of the two main sunspots undergo a sudden change in rotational motion during the impulsive phase of the flare. These results are discussed in the context of the Lorentz-force change that was proposed by Hudson et al. and Fisher et al. This mechanism can explain the connections between the rapid and irreversible photospheric vector magnetic field change and the observed short-term motions associated with the flare. In particular, the torque provided by the horizontal Lorentz force change agrees with what is required for the measured angular acceleration.

  8. Modeling particle loss in ventilation ducts

    E-Print Network [OSTI]

    Sippola, M R; Nazaroff, William W

    2003-01-01

    m) (c) 85% ASHRAE filters at air intake high-loss ducts low-loss ducts fractional fate (-) exhausted indoors indoorssurface deposition supply & return duct deposition filtered

  9. The synchrotron peak shift during high-energy flares of blazars

    E-Print Network [OSTI]

    M. Boettcher

    1999-02-10

    A prediction for the energy shift of the synchrotron spectrum of flat-spectrum radio quasars (FSRQs) during high-energy flares is presented. If the $\\gamma$-ray emission of FSRQs is produced by Comptonization of external radiation, then the peak of the synchrotron spectrum is predicted to move to lower energies in the flare state. This is opposite to the well-known broadband spectral behavior of high-frequency peaked BL-Lac objects where the external radiation field is believed to be weak and synchrotron-self Compton scattering might be the dominant $\\gamma$-ray radiation mechanism. The synchrotron peak shift, if observed in FSRQs, can thus be used as a diagnostic to determine the dominant radiation mechanism in these objects. I suggest a few FSRQs as promising candidates to test the prediction of the external-Comptonization model.

  10. Power Laws in Solar Flares: Self-Organized Criticality or Turbulence?

    E-Print Network [OSTI]

    Guido Boffetta; Vincenzo Carbone; Paolo Giuliani; Pierluigi Veltri; Angelo Vulpiani

    1999-04-23

    We study the time evolution of Solar Flares activity by looking at the statistics of quiescent times $\\tau_{L}$ between successive bursts. The analysis of 20 years of data reveals a power law distribution with exponent $\\alpha \\simeq 2.4$ which is an indication of complex dynamics with long correlation times. The observed scaling behavior is in contradiction with the Self-Organized Criticality models of Solar Flares which predict Poisson-like statistics. Chaotic models, including the destabilization of the laminar phases and subsequent restabilization due to nonlinear dynamics, are able to reproduce the power law for the quiescent times. In the case of the more realistic Shell Model of MHD turbulence we are able to reproduce all the observed distributions.

  11. The Cause of Photospheric and Helioseismic Responses to Solar Flares: High-Energy Electrons or Protons?

    E-Print Network [OSTI]

    A. G. Kosovichev

    2007-10-03

    Analysis of the hydrodynamic and helioseismic effects in the photosphere during the solar flare of July 23, 2002, observed by Michelson Doppler Imager (MDI) on SOHO, and high-energy images from RHESSI shows that these effects are closely associated with sources of the hard X-ray emission, and that there are no such effects in the centroid region of the flare gamma-ray emission. These results demonstrate that contrary to expectations the hydrodynamic and helioseismic responses (''sunquakes") are more likely to be caused by accelerated electrons than by high-energy protons. A series of multiple impulses of high-energy electrons forms a hydrodynamic source moving in the photosphere with a supersonic speed. The moving source plays a critical role in the formation of the anisotropic wave front of sunquakes.

  12. Quasi-Periodic Formaldehyde Maser Flares in the Massive Protostellar Object IRAS18566+0408

    E-Print Network [OSTI]

    Araya, E D; Goss, W M; Kurtz, S; Richards, A M S; Linz, H; Olmi, L; Sewilo, M

    2010-01-01

    We report results of an extensive observational campaign of the 6 cm formaldehyde maser in the young massive stellar object IRAS18566+0408 (G37.55+0.20) conducted from 2002 to 2009. Using Arecibo, VLA, and GBT, we discovered quasi-periodic formaldehyde flares (P ~ 237 days). Based on Arecibo observations, we also discovered correlated variability between formaldehyde (H2CO) and methanol (CH3OH) masers. The H2CO and CH3OH masers are not spatially coincident, as demonstrated by different line velocities and high angular resolution MERLIN observations. The flares could be caused by variations in the infrared radiation field, possibly modulated by periodic accretion onto a young binary system.

  13. Statistics and Classification of the Microwave Zebra Patterns Associated with Solar Flares

    E-Print Network [OSTI]

    Tan, Baolin; Zhang, Yin; Meszarosova, H; Karlicky, M

    2013-01-01

    The microwave zebra pattern (ZP) is the most interesting, intriguing, and complex spectral structure frequently observed in solar flares. A comprehensive statistical study will certainly help us to understand the formation mechanism, which is not exactly clear now. This work presents a comprehensive statistical analysis on a big sample with 202 ZP events collected from observations at the Chinese Solar Broadband Radio Spectrometer at Huairou and the Ondrejov Radiospectrograph in Czech Republic at frequencies of 1.00 - 7.60 GHz during 2000 - 2013. After investigating the parameter properties of ZPs, such as the occurrence in flare phase, frequency range, polarization degree, duration, etc., we find that the variation of zebra stripe frequency separation with respect to frequency is the best indicator for a physical classification of ZPs. Microwave ZPs can be classified into 3 types: equidistant ZP, variable-distant ZP, and growing-distant ZP, possibly corresponding to mechanisms of Bernstein wave model, whistl...

  14. Quasi-periodic wiggles of microwave zebra structures in a solar flare

    E-Print Network [OSTI]

    Yu, Sijie; Selzer, L A; Tan, Baolin; Yan, Yihua

    2013-01-01

    Quasi-periodic wiggles of microwave zebra pattern structures with period range from about 0.5 s to 1.5 s are found in a X-class solar flare on 2006 December 13 at the 2.6-3.8 GHz with the Chinese Solar Broadband Radio Spectrometer (SBRS/Huairou). Periodogram and correlation analysis show that the wiggles have two-three significant periodicities and almost in phase between stripes at different frequency. The Alfven speed estimated from the zebra pattern structures is about 700 Km/s. We obtain the spatial size of the waveguiding plasma structure to be about 1 Mm with the detected period of about 1 s. It suggests the ZP wiggles can be associated with the fast mag- netoacoustic oscillations in the flaring active region. The lack of a significant phase shift between wiggles of different stripes suggests that the ZP wiggles are caused by a standing sausage oscillation.

  15. Numerical Study of a Propagating Non-Thermal Microwave Feature in a Solar Flare Loop

    E-Print Network [OSTI]

    T. Minoshima; T. Yokoyama

    2008-06-24

    We analytically and numerically study the motion of electrons along a magnetic loop, to compare with the observation of the propagating feature of the non-thermal microwave source in the 1999 August 28 solar flare reported by Yokoyama et al. (2002). We model the electron motion with the Fokker-Planck equation and calculate the spatial distribution of the gyrosynchrotron radiation. We find that the microwave propagating feature does not correspond to the motion of electrons with a specific initial pitch angle. This apparent propagating feature is a consequence of the motion of an ensemble of electrons with different initial pitch angles, which have different time and position to produce strong radiation in the loop. We conclude that the non-thermal electrons in the 1999 August 28 flare were isotropically accelerated and then are injected into the loop.

  16. Wetland Losses and Human Impacts

    E-Print Network [OSTI]

    Gray, Matthew

    American Wetlands Peatlands of Alaska and Canada Playa Lakes MAV Prairie Potholes Coastal Wetlands mil ha (89 mil) ·Alaska =69 mil ha United States: =127 mil haCanada: =111 mil ha Manitoba (22.5) Ontario (29.2) = 51.7 mil ha 41% 53% Loss** =238 mil ha Canada 53% Alaska 29% Lower US 18%Lower US 29

  17. Saving Lives and Mitigating Losses

    E-Print Network [OSTI]

    Duchowski, Andrew T.

    Saving Lives and Mitigating Losses Wind and Structural Engineering Research Facility #12;Clemson University's Wind and Structural Engineering Research (WiSER) Facility is a premier laboratory for the study of wind effects on structures. Testing to assess the structural performance of buildings and bridges can

  18. Sub-terahertz, microwaves and high energy emissions during the December 6, 2006 flare, at 18:40 UT

    E-Print Network [OSTI]

    Pierre Kaufmann; Gerard Trottet; C. Guillermo Gimenez de Castro; Jean-Pierre Raulin; Sam Krucker; Albert Y. Shih; Hugo Levato

    2008-12-17

    The presence of a solar burst spectral component with flux density increasing with frequency in the sub-terahertz range, spectrally separated from the well-known microwave spectral component, bring new possibilities to explore the flaring physical processes, both observational and theoretical. The solar event of 6 December 2006, starting at about 18:30 UT, exhibited a particularly well-defined double spectral structure, with the sub-THz spectral component detected at 212 and 405 GHz by SST and microwaves (1-18 GHz) observed by the Owens Valley Solar Array (OVSA). Emissions obtained by instruments in satellites are discussed with emphasis to ultra-violet (UV) obtained by the Transition Region And Coronal Explorer (TRACE), soft X-rays from the Geostationary Operational Environmental Satellites (GOES) and X- and gamma-rays from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The sub-THz impulsive component had its closer temporal counterpart only in the higher energy X- and gamma-rays ranges. The spatial positions of the centers of emission at 212 GHz for the first flux enhancement were clearly displaced by more than one arc-minute from positions at the following phases. The observed sub-THz fluxes and burst source plasma parameters were found difficult to be reconciled to a purely thermal emission component. We discuss possible mechanisms to explain the double spectral components at microwaves and in the THz ranges.

  19. MODELING OF GYROSYNCHROTRON RADIO EMISSION PULSATIONS PRODUCED BY MAGNETOHYDRODYNAMIC LOOP OSCILLATIONS IN SOLAR FLARES

    SciTech Connect (OSTI)

    Mossessian, George; Fleishman, Gregory D. [Center For Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102 (United States)

    2012-04-01

    A quantitative study of the observable radio signatures of the sausage, kink, and torsional magnetohydrodynamic (MHD) oscillation modes in flaring coronal loops is performed. Considering first non-zero order effect of these various MHD oscillation modes on the radio source parameters such as magnetic field, line of sight, plasma density and temperature, electron distribution function, and the source dimensions, we compute time-dependent radio emission (spectra and light curves). The radio light curves (of both flux density and degree of polarization) at all considered radio frequencies are then quantified in both time domain (via computation of the full modulation amplitude as a function of frequency) and in Fourier domain (oscillation spectra, phases, and partial modulation amplitude) to form the signatures specific to a particular oscillation mode and/or source parameter regime. We found that the parameter regime and the involved MHD mode can indeed be distinguished using the quantitative measures derived in the modeling. We apply the developed approach to analyze radio burst recorded by Owens Valley Solar Array and report possible detection of the sausage mode oscillation in one (partly occulted) flare and kink or torsional oscillations in another flare.

  20. Collisional relaxation of electrons in a warm plasma and accelerated nonthermal electron spectra in solar flares

    E-Print Network [OSTI]

    Kontar, E P; Emslie, A G; Bian, N H

    2015-01-01

    Extending previous studies of nonthermal electron transport in solar flares which include the effects of collisional energy diffusion and thermalization of fast electrons, we present an analytic method to infer more accurate estimates of the accelerated electron spectrum in solar flares from observations of the hard X-ray spectrum. Unlike for the standard cold-target model, the spatial characteristics of the flaring region, especially the necessity to consider a finite volume of hot plasma in the source, need to be taken into account in order to correctly obtain the injected electron spectrum from the source-integrated electron flux spectrum (a quantity straightforwardly obtained from hard X-ray observations). We show that, for a given source-integrated electron flux spectrum, the overall power in the injected electrons could be reduced by an order of magnitude or more relative to its cold-target value. Indeed, the extent of electron thermalization can be significant enough to nullify the need to introduce an...

  1. Spectral characteristics of Mrk 501 during the 2012 and 2014 flaring states

    E-Print Network [OSTI]

    Cologna, Gabriele; Mohamed, Mahmoud; Rieger, Frank; Romoli, Carlo; Taylor, Andrew; Wagner, Stefan J; Wierzcholska, Alicja; Jacholkowska, Agnieszka; Kurtanidze, Omar

    2015-01-01

    Observations at Very High Energies (VHE, E > 100 GeV) of the BL Lac object Mrk 501 taken with the High Energy Stereoscopic System (H.E.S.S.) in four distinct periods between 2004 and 2014 are presented, with focus on the 2012 and 2014 flaring states. The source is detected with high significance above $\\sim$ 2 TeV in $\\sim$ 13.1 h livetime. The observations comprise low flux states and strong flaring events, which in 2014 show a flux level comparable to the 1997 historical maximum. Such high flux states enable spectral variability and flux variability studies down to a timescale of four minutes in the 2-20 TeV energy range. During the 2014 flare, the source is clearly detected in each of these bins. The intrinsic spectrum is well described by a power law of index $\\Gamma=2.15\\pm0.06$ and does not show curvature in this energy range. Flux dependent spectral analyses show a clear harder-when-brighter behaviour. The high flux levels and the high sensitivity of H.E.S.S. allow studies in the unprecedented combinat...

  2. ESTIMATING THE PROPERTIES OF HARD X-RAY SOLAR FLARES BY CONSTRAINING MODEL PARAMETERS

    SciTech Connect (OSTI)

    Ireland, J. [ADNET Systems, Inc. at NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Tolbert, A. K.; Schwartz, R. A. [Catholic University of America at NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Holman, G. D.; Dennis, B. R. [NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States)

    2013-06-01

    We wish to better constrain the properties of solar flares by exploring how parameterized models of solar flares interact with uncertainty estimation methods. We compare four different methods of calculating uncertainty estimates in fitting parameterized models to Ramaty High Energy Solar Spectroscopic Imager X-ray spectra, considering only statistical sources of error. Three of the four methods are based on estimating the scale-size of the minimum in a hypersurface formed by the weighted sum of the squares of the differences between the model fit and the data as a function of the fit parameters, and are implemented as commonly practiced. The fourth method is also based on the difference between the data and the model, but instead uses Bayesian data analysis and Markov chain Monte Carlo (MCMC) techniques to calculate an uncertainty estimate. Two flare spectra are modeled: one from the Geostationary Operational Environmental Satellite X1.3 class flare of 2005 January 19, and the other from the X4.8 flare of 2002 July 23. We find that the four methods give approximately the same uncertainty estimates for the 2005 January 19 spectral fit parameters, but lead to very different uncertainty estimates for the 2002 July 23 spectral fit. This is because each method implements different analyses of the hypersurface, yielding method-dependent results that can differ greatly depending on the shape of the hypersurface. The hypersurface arising from the 2005 January 19 analysis is consistent with a normal distribution; therefore, the assumptions behind the three non-Bayesian uncertainty estimation methods are satisfied and similar estimates are found. The 2002 July 23 analysis shows that the hypersurface is not consistent with a normal distribution, indicating that the assumptions behind the three non-Bayesian uncertainty estimation methods are not satisfied, leading to differing estimates of the uncertainty. We find that the shape of the hypersurface is crucial in understanding the output from each uncertainty estimation technique, and that a crucial factor determining the shape of hypersurface is the location of the low-energy cutoff relative to energies where the thermal emission dominates. The Bayesian/MCMC approach also allows us to provide detailed information on probable values of the low-energy cutoff, E{sub c} , a crucial parameter in defining the energy content of the flare-accelerated electrons. We show that for the 2002 July 23 flare data, there is a 95% probability that E{sub c} lies below approximately 40 keV, and a 68% probability that it lies in the range 7-36 keV. Further, the low-energy cutoff is more likely to be in the range 25-35 keV than in any other 10 keV wide energy range. The low-energy cutoff for the 2005 January 19 flare is more tightly constrained to 107 {+-} 4 keV with 68% probability. Using the Bayesian/MCMC approach, we also estimate for the first time probability density functions for the total number of flare-accelerated electrons and the energy they carry for each flare studied. For the 2002 July 23 event, these probability density functions are asymmetric with long tails orders of magnitude higher than the most probable value, caused by the poorly constrained value of the low-energy cutoff. The most probable electron power is estimated at 10{sup 28.1} erg s{sup -1}, with a 68% credible interval estimated at 10{sup 28.1}-10{sup 29.0} erg s{sup -1}, and a 95% credible interval estimated at 10{sup 28.0}-10{sup 30.2} erg s{sup -1}. For the 2005 January 19 flare spectrum, the probability density functions for the total number of flare-accelerated electrons and their energy are much more symmetric and narrow: the most probable electron power is estimated at 10{sup 27.66{+-}0.01} erg s{sup -1} (68% credible intervals). However, in this case the uncertainty due to systematic sources of error is estimated to dominate the uncertainty due to statistical sources of error.

  3. Standing Sausage Modes In Nonuniform Magnetic Tubes: An Inversion Scheme For Inferring Flare Loop Parameters

    E-Print Network [OSTI]

    Chen, Shao-Xia; Xiong, Ming; Yu, Hui; Guo, Ming-Zhe

    2015-01-01

    Standing sausage modes in flare loops are important for interpreting quasi-periodic pulsations (QPPs) in solar flare lightcurves. We propose an inversion scheme that consistently uses their periods $P$ and damping times $\\tau$ to diagnose flare loop parameters. We derive a generic dispersion relation governing linear sausage waves in pressure-less straight tubes, for which the transverse density inhomogeneity takes place in a layer of arbitrary width $l$ and is of arbitrary form. We find that $P$ and $\\tau$ depend on the combination of $[R/v_{\\rm Ai}, L/R, l/R, \\rho_{\\rm i}/\\rho_{\\rm e}]$, where $R$ is the loop radius, $L$ is the looplength, $v_{\\rm Ai}$ is the internal Alfv\\'en speed, and $\\rho_{\\rm i}/\\rho_{\\rm e}$ is the density contrast. For all the density profiles examined, $P$ and $\\tau$ experience saturation when $L/R \\gg 1$, yielding an inversion curve in the $[R/v_{\\rm Ai}, l/R, \\rho_{\\rm i}/\\rho_{\\rm e}]$ space with a specific density profile when $L/R$ is sufficiently large. When applied to a spat...

  4. Study of multi-periodic coronal pulsations during an X-class solar flare

    E-Print Network [OSTI]

    Chowdhury, Partha; Dwivedi, B N; Sych, Robert; Moon, Y -J

    2015-01-01

    We investigate quasi-periodic coronal pulsations during the decay phase of an X 3.2 class flare on 14 May 2013, using soft X-ray data from the RHESSI satellite. Periodogram analyses of soft X-ray light curves show that 53 s and 72 s periods co-exist in the 3-6, 6-12 and 12-25 KeV energy bands. Considering the typical length of the flaring loop system and observed periodicities, we find that they are associated with multiple (first two harmonics) of fast magnetoacoustic sausage waves. The phase relationship of soft X-ray emissions in different energy bands using cross-correlation technique show that these modes are standing in nature as we do not find the phase lag. Considering the period ratio, we diagnose the local plasma conditions of the flaring region by invoking MHD seismology. The period ratio P1/2P2 is found to be 0.65, which indicates that such oscillations are most likely excited in longitudinal density stratified loops.

  5. On the 2012 October 23 circular ribbon flare: emission features and magnetic topology

    E-Print Network [OSTI]

    Yang, Kai; Ding, M D

    2015-01-01

    Circular ribbon flares are usually related to spine-fan type magnetic topology containing null-points. In this paper, we investigate an X-class circular ribbon flare on 2012 October 23, using the multi-wavelength data from the \\textit{Solar Dynamics Observatory}, \\textit{Hinode}, and the \\textit{Ramaty High Energy Solar Spectroscopic Imager}. In \\ion{Ca}{2} H emission, the flare showed three ribbons with two highly elongated ones inside and outside a quasi-circular one, respectively. A hot channel was displayed in the extreme ultraviolet (EUV) emissions that infers the existence of a magnetic flux rope. Two hard X-ray (HXR) sources in the 12--25 keV energy band were located at the footpoints of this hot channel. Using a nonlinear force-free magnetic field extrapolation, we identify three topological structures: (1) a 3D null-point, (2) a flux rope below the fan of the null-point, and (3) a large-scale quasi-separatrix layers (QSL) induced by the quadrupolar-like magnetic field of the active region. We find th...

  6. Time-Dependent Modeling of Gamma-ray Flares in Blazar PKS1510-089

    E-Print Network [OSTI]

    Saito, Shinya; Tanaka, Yasuyuki; Takahashi, Tadayuki; Sikora, Marek; Moderski, Rafal

    2015-01-01

    Here we present a new approach for constraining luminous blazars, incorporating fully time-dependent and self-consistent modeling of bright gamma-ray flares of PKS1510-089 resolved with Fermi-LAT, in the framework of the internal shock scenario. The results of our modeling imply the location of the gamma-ray flaring zone outside of the broad-line region, namely around 0.3pc from the core for a free-expanding jet with the opening angle Gamma, \\theta_\\mathrm{jet} \\simeq 1 (where Gamma is the jet bulk Lorentz factor), up to \\simeq 3pc for a collimated outflow with Gamma, \\theta_\\mathrm{jet} \\simeq 0.1. Moreover, under the Gamma, \\theta_\\mathrm{jet} \\simeq 1 condition, our modeling indicates the maximum efficiency of the jet production during the flares, with the total jet energy flux strongly dominated by protons and exceeding the available accretion power in the source. This is in contrast to the quiescence states of the blazar, characterized by lower jet kinetic power and an approximate energy equipartition be...

  7. Comparative Analysis of Non-thermal Emissions and Study of Electron Transport in a Solar Flare

    E-Print Network [OSTI]

    T. Minoshima; T. Yokoyama; N. Mitani

    2007-10-02

    We study the non-thermal emissions in a solar flare occurring on 2003 May 29 by using RHESSI hard X-ray (HXR) and Nobeyama microwave observations. This flare shows several typical behaviors of the HXR and microwave emissions: time delay of microwave peaks relative to HXR peaks, loop-top microwave and footpoint HXR sources, and a harder electron energy distribution inferred from the microwave spectrum than from the HXR spectrum. In addition, we found that the time profile of the spectral index of the higher-energy ($\\gsim 100$ keV) HXRs is similar to that of the microwaves, and is delayed from that of the lower-energy ($\\lsim 100$ keV) HXRs. We interpret these observations in terms of an electron transport model called {\\TPP}. We numerically solved the spatially-homogeneous {\\FP} equation to determine electron evolution in energy and pitch-angle space. By comparing the behaviors of the HXR and microwave emissions predicted by the model with the observations, we discuss the pitch-angle distribution of the electrons injected into the flare site. We found that the observed spectral variations can qualitatively be explained if the injected electrons have a pitch-angle distribution concentrated perpendicular to the magnetic field lines rather than isotropic distribution.

  8. A simple model of chromospheric evaporation and condensation driven conductively in a solar flare

    SciTech Connect (OSTI)

    Longcope, D. W.

    2014-11-01

    Magnetic energy released in the corona by solar flares reaches the chromosphere where it drives characteristic upflows and downflows known as evaporation and condensation. These flows are studied here for the case where energy is transported to the chromosphere by thermal conduction. An analytic model is used to develop relations by which the density and velocity of each flow can be predicted from coronal parameters including the flare's energy flux F. These relations are explored and refined using a series of numerical investigations in which the transition region (TR) is represented by a simplified density jump. The maximum evaporation velocity, for example, is well approximated by v{sub e} ? 0.38(F/?{sub co,} {sub 0}){sup 1/3}, where ?{sub co,} {sub 0} is the mass density of the pre-flare corona. This and the other relations are found to fit simulations using more realistic models of the TR both performed in this work, and taken from a variety of previously published investigations. These relations offer a novel and efficient means of simulating coronal reconnection without neglecting entirely the effects of evaporation.

  9. Adjustable Speed- A Tool for Saving Energy Losses in Pumps, Fans, Fans, Blowers and Compressors 

    E-Print Network [OSTI]

    Hickok, H. N.

    1985-01-01

    Petroleum and chemical plants of today are effectively cutting energy losses in their plants thermally, electrically, and mechanically in their process equipment. In rotating process equipment such as pumps, fans, compressors, and blowers, much...

  10. RHESSI Observations of the Solar Flare Iron-line Feature at 6.7 keV

    E-Print Network [OSTI]

    K. J. H. Phillips; C. Chifor; B. R. Dennis

    2006-07-13

    Analysis of RHESSI 3--10 keV spectra for 27 solar flares is reported. This energy range includes thermal free--free and free--bound continuum and two line features, at 6.7keV and 8keV, principally due to highly ionized iron (Fe). We used the continuum and the flux in the so-called Fe-line feature at 6.7keV to derive the electron temperature T_e, the emission measure, and the Fe-line equivalent width as functions of time in each flare. The Fe/H abundance ratio in each flare is derived from the Fe-line equivalent width as a function of T_e. To minimize instrumental problems with high count rates and effects associated with multi-temperature and nonthermal spectral components, spectra are presented mostly during the flare decay phase, when the emission measure and temperature were smoothly varying. We found flare Fe/H abundance ratios that are consistent with the coronal abundance of Fe (i.e. 4 times the photospheric abundance) to within 20% for at least 17 of the 27 flares; for 7 flares, the Fe/H abundance ratio is possibly higher by up to a factor of 2. We find evidence that the Fe XXV ion fractions are less than the theoretically predicted values by up to 60% at T_e=25 MK appear to be displaced from the most recent theoretical values by between 1 and 3 MK.

  11. Photosphere emission in the X-ray flares of swift gamma-ray bursts and implications for the fireball properties

    SciTech Connect (OSTI)

    Peng, Fang-Kun; Liang, En-Wei; Xi, Shao-Qiang; Lu, Rui-Jing; Zhang, Bing [Guangxi Key Laboratory for Relativistic Astrophysics, the Department of Physics, Guangxi University, Nanning 530004 (China); Wang, Xiang-Yu [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Hou, Shu-Jin [Institute of Physics and Electronic Engineering, Nanyang Normal College, Nanyang 473061 (China); Zhang, Jin, E-mail: lew@gxu.edu.cn, E-mail: xywang@nju.edu.cn, E-mail: zhang@physics.unlv.edu [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2014-11-10

    X-ray flares of gamma-ray bursts (GRBs) are usually observed in the soft X-ray range and the spectral coverage is limited. In this paper, we present an analysis of 32 GRB X-ray flares that are simultaneously observed by both Burst Alert Telescope and X-Ray Telescope on board the Swift mission, so that a joint spectral analysis with a wider spectral coverage is possible. Our results show that the joint spectra of 19 flares are fitted with the absorbed single power law or the Band function models. More interestingly, the joint spectra of the other 13 X-ray flares are fitted with the absorbed single power-law model plus a blackbody component. Phenomenally, the observed spectra of these 13 flares are analogous to several GRBs with a thermal component, but only with a much lower temperature of kT = 1 ? 3 keV. Assuming that the thermal emission is the photosphere emission of the GRB fireball, we derive the fireball properties of the 13 flares that have redshift measurements, such as the bulk Lorentz factor ?{sub ph} of the outflow. The derived ?{sub ph} range from 50 to 150 and a relation of ?{sub ph} to the thermal emission luminosity is found. It is consistent with the ?{sub 0} – L {sub iso} relations that are derived for the prompt gamma-ray emission. We discuss the physical implications of these results within the content of jet composition and the radiation mechanism of GRBs and X-ray flares.

  12. An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles

    E-Print Network [OSTI]

    V. V. Grechnev; V. G. Kurt; I. M. Chertok; A. M. Uralov; H. Nakajima; A. T. Altyntsev; A. V. Belov; B. Yu. Yushkov; S. N. Kuznetsov; L. K. Kashapova; N. S. Meshalkina; N. P. Prestage

    2008-06-30

    The extreme solar and SEP event of 20 January 2005 is analyzed from two perspectives. Firstly, we study features of the main phase of the flare, when the strongest emissions from microwaves up to 200 MeV gamma-rays were observed. Secondly, we relate our results to a long-standing controversy on the origin of SEPs arriving at Earth, i.e., acceleration in flares, or shocks ahead of CMEs. All emissions from microwaves up to 2.22 MeV line gamma-rays during the main flare phase originated within a compact structure located just above sunspot umbrae. A huge radio burst with a frequency maximum at 30 GHz was observed, indicating the presence of a large number of energetic electrons in strong magnetic fields. Thus, protons and electrons responsible for flare emissions during its main phase were accelerated within the magnetic field of the active region. The leading, impulsive parts of the GLE, and highest-energy gamma-rays identified with pi^0-decay emission, are similar and correspond in time. The origin of the pi^0-decay gamma-rays is argued to be the same as that of lower energy emissions. We estimate the sky-plane speed of the CME to be 2000-2600 km/s, i.e., high, but of the same order as preceding non-GLE-related CMEs from the same active region. Hence, the flare itself rather than the CME appears to determine the extreme nature of this event. We conclude that the acceleration, at least, to sub-relativistic energies, of electrons and protons, responsible for both the flare emissions and the leading spike of SEP/GLE by 07 UT, are likely to have occurred simultaneously within the flare region. We do not rule out a probable contribution from particles accelerated in the CME-driven shock for the leading GLE spike, which seemed to dominate later on.

  13. Thermochemical processing of digested sludge and its implications in the United States Jennifer Lawrence, Ruth Reed, Sara Tischhauser, Casey Zak

    E-Print Network [OSTI]

    Iglesia, Enrique

    , or biomethane) for meeting onsite heat #12;and power needs. Biogas is a methanerich byproduct of this process, or biomethane, is produced as a result of this process and can either be flared off to reduce greenhouse gas of anaerobic digestion (AD) to reduce sludge volumes as well as produce digester gas (also known as biogas

  14. Solar Magnetic Field Studies Using the 12-Micron Emission Lines. IV. Observations of a Delta-Region Solar Flare

    E-Print Network [OSTI]

    Donald E. Jennings; Drake Deming; George McCabe; Pedro Sada; Thomas Moran

    2001-12-05

    We have recently developed the capability to make solar vector (Stokes IQUV) magnetograms using the infrared line of MgI at 12.32 microns. On 24 April 2001, we obtained a vector magnetic map of solar active region NOAA 9433, fortuitously just prior to the occurrence of an M2 flare. Examination of a sequence of SOHO/MDI magnetograms, and comparison with ground-based H-alpha images, shows that the flare was produced by the cancellation of newly emergent magnetic flux outside of the main sunspot. The very high Zeeman-sensitivity of the 12-micron data allowed us to measure field strengths on a spatial scale which was not directly resolvable. At the flare trigger site, opposite polarity fields of 2700 and 1000 Gauss occurred within a single 2 arc-sec resolution element, as revealed by two resolved Zeeman splittings in a single spectrum. Our results imply an extremely high horizontal field strength gradient (5 G/km) prior to the flare, significantly greater than seen in previous studies. We also find that the magnetic energy of the cancelling fields was more than sufficient to account for the flare's X-ray luminosity.

  15. Origin of the 30 THz emission detected during the 2012 March 13 solar flare at 17:20 UT

    E-Print Network [OSTI]

    Trottet, G; MacKinnon, A; de Castro, G Giménez; Simões, P J A; Cabezas, D; de La Luz, V; Luoni, M; Kaufmann, P

    2015-01-01

    Solar observations in the infrared domain can bring important clues on the response of the low solar atmosphere to primary energy released during flares. At present the infrared continuum has been detected at 30 THz (10 $\\mu$m) in only a few flares. In this work we present a detailed multi-frequency analysis of SOL2012-03-13, including observations at radio millimeter and sub-millimeter wavelengths, in hard X-rays (HXR), gamma-rays (GR), H-alpha, and white-light. HXR/GR spectral analysis shows that the event is a GR line flare and allows estimating the numbers of and energy contents in electrons, protons and alpha particles produced during the flare. The energy spectrum of the electrons producing the HXR/GR continuum is consistent with a broken power-law with an energy break at ~800 keV. It is shown that the high-energy part (above ~800 keV) of this distribution is responsible for the high-frequency radio emission (> 20 GHz) detected during the flare. By comparing the 30 THz emission expected from semi-empiri...

  16. South Dakota Natural Gas Vented and Flared (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home PageMonthly","10/2015"4,"Ames5 Tables July 1996 Energy Information Administration Office of Coal, Nuclear,DecadeYearbyWithdrawals (MillionYearProcessedDecade Year-0 Year-1

  17. South Dakota Natural Gas Vented and Flared (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home PageMonthly","10/2015"4,"Ames5 Tables July 1996 Energy Information Administration Office of Coal, Nuclear,DecadeYearbyWithdrawals (MillionYearProcessedDecade Year-0

  18. Quantum cryptographic system with reduced data loss

    DOE Patents [OSTI]

    Lo, H.K.; Chau, H.F.

    1998-03-24

    A secure method for distributing a random cryptographic key with reduced data loss is disclosed. Traditional quantum key distribution systems employ similar probabilities for the different communication modes and thus reject at least half of the transmitted data. The invention substantially reduces the amount of discarded data (those that are encoded and decoded in different communication modes e.g. using different operators) in quantum key distribution without compromising security by using significantly different probabilities for the different communication modes. Data is separated into various sets according to the actual operators used in the encoding and decoding process and the error rate for each set is determined individually. The invention increases the key distribution rate of the BB84 key distribution scheme proposed by Bennett and Brassard in 1984. Using the invention, the key distribution rate increases with the number of quantum signals transmitted and can be doubled asymptotically. 23 figs.

  19. Quantum cryptographic system with reduced data loss

    DOE Patents [OSTI]

    Lo, Hoi-Kwong (1309, Low Block, Lei Moon House Ap Lei Chau Estate, Hong Kong, HK); Chau, Hoi Fung (Flat C, 42nd Floor, Tower 1, University Heights 23 Pokfield Road, Pokfulam, Hong Kong, HK)

    1998-01-01

    A secure method for distributing a random cryptographic key with reduced data loss. Traditional quantum key distribution systems employ similar probabilities for the different communication modes and thus reject at least half of the transmitted data. The invention substantially reduces the amount of discarded data (those that are encoded and decoded in different communication modes e.g. using different operators) in quantum key distribution without compromising security by using significantly different probabilities for the different communication modes. Data is separated into various sets according to the actual operators used in the encoding and decoding process and the error rate for each set is determined individually. The invention increases the key distribution rate of the BB84 key distribution scheme proposed by Bennett and Brassard in 1984. Using the invention, the key distribution rate increases with the number of quantum signals transmitted and can be doubled asymptotically.

  20. Flare Ribbons Observed with G-band and FeI 6302A Filters of the Solar Optical Telescope on Board Hinode

    E-Print Network [OSTI]

    H. Isobe; M. Kubo; T. Minoshima; K. Ichimoto; Y. Katsukawa; T. D. Tarbell; S. Tsuneta; T. E. Berger; B. W. Lites; S. Nagata; T. Shimizu; R. A. Shine; Y. Suematsu; A. Title

    2007-11-26

    The Solar Optical Telescope (SOT) on board Hinode satellite observed an X3.4 class flare on 2006 December 13. Typical two-ribbon structure was observed, not only in the chromospheric CaII H line but also in G-band and FeI 6302A line. The high-resolution, seeing-free images achieved by SOT revealed, for the first time, the sub-arcsec fine structures of the "white light" flare. The G-band flare ribbons on sunspot umbrae showed a sharp leading edge followed by a diffuse inside, as well as previously known core-halo structure. The underlying structures such as umbral dots, penumbral filaments and granules were visible in the flare ribbons. Assuming that the sharp leading edge was directly heated by particle beam and the diffuse parts were heated by radiative back-warming, we estimate the depth of the diffuse flare emission using the intensity profile of the flare ribbon. We found that the depth of the diffuse emission is about 100 km or less from the height of the source of radiative back-warming. The flare ribbons were also visible in the Stokes-V images of FeI 6302A, as a transient polarity reversal. This is probably related to "magnetic transient" reported in the literature. The intensity increase in Stokes-I images indicates that the FeI 6302A line was significantly deformed by the flare, which may cause such a magnetic transient.

  1. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Refinements to flare energy estimates -a follow-up to "Energy

    E-Print Network [OSTI]

    California at Berkeley, University of

    to arrive at an overall energy budget for the event. The best estimates for the energies of the variousJOURNAL OF GEOPHYSICAL RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Refinements to flare energy estimates - a follow-up to "Energy Partition in Two Solar Flare/CME Events" A. G. Emslie, 1 B. R. Dennis 2

  2. QUIESCENT RADIO EMISSION FROM SOUTHERN LATE-TYPE M DWARFS AND A SPECTACULAR RADIO FLARE FROM THE M8 DWARF DENIS 10483956

    E-Print Network [OSTI]

    Burgasser, Adam J.

    QUIESCENT RADIO EMISSION FROM SOUTHERN LATE-TYPE M DWARFS AND A SPECTACULAR RADIO FLARE FROM THE M8 at the Australia Telescope Compact Array to search for quiescent and flaring emission from seven nearby Southern detected in quiescent emission at 4.80 GHz. The observed emission is consistent with optically thin

  3. Numerical examination of plasmoid-induced reconnection model for solar flares: the relation between plasmoid velocity and reconnection rate

    E-Print Network [OSTI]

    Keisuke Nishida; Masaki Shimizu; Daikou Shiota; Hiroyuki Takasaki; Tetsuya Magara; Kazunari Shibata

    2008-09-04

    The plasmoid-induced-reconnection model explaining solar flares based on bursty reconnection produced by an ejecting plasmoid suggests a possible relation between the ejection velocity of a plasmoid and the rate of magnetic reconnection. In this study, we focus on the quantitative description of this relation. We performed magnetohydrodynamic (MHD) simulations of solar flares by changing the values of resistivity and the plasmoid velocity. The plasmoid velocity has been changed by applying an additional force to the plasmoid to see how the plasmoid velocity affects the reconnection rate. An important result is that the reconnection rate has a positive correlation with the plasmoid velocity, which is consistent with the plasmoid-induced-reconnection model for solar flares. We also discuss an observational result supporting this positive correlation.

  4. Hard X-ray Spectra and Positions of Solar Flares observed by RHESSI: photospheric albedo, directivity and electron spectra

    E-Print Network [OSTI]

    J. Kasparova; E. P. Kontar; J. C. Brown

    2007-01-30

    We investigate the signature of the photospheric albedo contribution in solar flare hard X-ray spectra, the effect of low energy cutoffs in electron spectra, and the directivity of hard X-ray emission. Using Ramaty High Energy Solar Spectroscopic Imager (RHESSI) flare data we perform a statistical analysis of spatially integrated spectra and positions of solar flares. We demonstrate clear centre-to-limb variation of photon spectral indices in the 15-20 keV energy range and a weaker dependency in the 20-50 keV range which is consistent with photospheric albedo as the cause. The results also suggest that low-energy cutoffs sometimes inferred in mean electron spectra are an artefact of albedo. We also derive the anisotropy (ratio of downward/observer directed photons) of hard X-ray emission in the 15-20 keV range for various heliocentric angles.

  5. A flare observed in coronal, transition region, and helium I 10830 Å emissions

    SciTech Connect (OSTI)

    Zeng, Zhicheng; Cao, Wenda; Qiu, Jiong; Judge, Philip G.

    2014-10-01

    On 2012 June 17, we observed the evolution of a C-class flare associated with the eruption of a filament near a large sunspot in the active region NOAA 11504. We obtained high spatial resolution filtergrams using the 1.6 m New Solar Telescope at the Big Bear Solar Observatory in broadband TiO at 706 nm (bandpass: 10 Å) and He I 10830 Å narrow band (bandpass: 0.5 Å, centered 0.25 Å to the blue). We analyze the spatio-temporal behavior of the He I 10830 Å data, which were obtained over a 90''×90'' field of view with a cadence of 10 s. We also analyze simultaneous data from the Atmospheric Imaging Assembly and Extreme Ultraviolet Variability Experiment instruments on board the Solar Dynamics Observatory spacecraft, and data from the Reuven Ramaty High Energy Solar Spectroscopic Imager and GOES spacecrafts. Non-thermal effects are ignored in this analysis. Several quantitative aspects of the data, as well as models derived using the '0D' enthalpy-based thermal evolution of loops model code, indicate that the triplet states of the 10830 Å multiplet are populated by photoionization of chromospheric plasma followed by radiative recombination. Surprisingly, the He II 304 Å line is reasonably well matched by standard emission measure calculations, along with the C IV emission which dominates the Atmosphere Imaging Assembly 1600 Å channel during flares. This work lends support to some of our previous work combining X-ray, EUV, and UV data of flares to build models of energy transport from corona to chromosphere.

  6. Loss mechanisms in turbine tip clearance flows

    E-Print Network [OSTI]

    Huang, Arthur (Arthur C.)

    2011-01-01

    Numerical simulations of tip clearance ow have been carried out to dene the loss generation mechanisms associated with tip leakage in unshrouded axial turbines. Mix- ing loss between the leakage, which takes the form of a ...

  7. The "skinny" on healthy weight loss

    E-Print Network [OSTI]

    Shoubridge, Eric

    restrictions One size does not fit all Taboos lead to overconsumption #12;Disadvantages ­Yo-Yo Dieting ENERGY IN ENERGY OUT WEIGHT LOSSWEIGHT GAIN #12;What is "healthy" weight loss? Steady weight loss (1

  8. Country Music and the Expression of Loss

    E-Print Network [OSTI]

    Harmon, Marcus Desmond

    2008-01-01

    Country Music and the Expression of Loss The recipient ofLoss, and mourning in the music of Emmylou Harris by Marcusthe intersection between music and cultural practice. In my

  9. Power losses in electrical networks depending on weather conditions

    SciTech Connect (OSTI)

    Zhelezko, Yu. S.; Kostyushko, V. A.; Krylov, S. V.; Nikiforov, E. P.; Savchenko, O. V.; Timashova, L. V.; Solomonik, E. A. [Electric Power Research Institute (VNIIE) (Russian Federation)

    2005-01-15

    Specific power losses to corona and to leakage currents over overhead insulators are presented for 110 - 750-kV transmission lines with different phase design and pole types for different weather conditions. Consumption of electric energy for ice melting on conductors of various cross sections is evaluated. Meteorological data of 1372 weather stations in Russia are processed for a period of 10 years. The territory of the country is divided into 7 regions with approximately homogeneous weather conditions. Specific power losses to corona and leakage currents over overhead insulators are presented for every region.

  10. Detecting Flaring Structures in Sagittarius A* with (Sub)Millimeter VLBI

    E-Print Network [OSTI]

    Vincent L. Fish; Sheperd S. Doeleman; Avery E. Broderick; Abraham Loeb; Alan E. E. Rogers

    2008-07-15

    Multiwavelength monitoring observations of Sagittarius A* exhibit variability on timescales of minutes to hours, indicating emission regions localized near the event horizon. (Sub)Millimeter-wavelength VLBI is uniquely suited to probe the environment of the assumed black hole on these scales. We consider a range of orbiting hot-spot and accretion-disk models and find that periodicity in Sgr A* flares is detectable using closure quantities. Our methods are applicable to any model producing source structure changes near the black hole, including jets and magnetohydrodynamic disk instabilities, and suggest that (sub)millimeter VLBI will play a prominent role in investigating Sgr A* near the event horizon.

  11. Induction machine stray loss from inter-bar currents

    E-Print Network [OSTI]

    Englebretson, Steven Carl

    2009-01-01

    Stray load loss refers generally to the sources of induction machine loss not accounted for by typical calculations of primary or secondary copper loss, no load core loss, or friction and windage loss. Harmonic rotor bar ...

  12. 7, 1009710129, 2007 Chemical ozone loss

    E-Print Network [OSTI]

    ACPD 7, 10097­10129, 2007 Chemical ozone loss in the Arctic winter 1991­1992 S. Tilmes et al. Title Chemistry and Physics Discussions Chemical ozone loss in the Arctic winter 1991­1992 S. Tilmes 1 , R. M Chemical ozone loss in the Arctic winter 1991­1992 S. Tilmes et al. Title Page Abstract Introduction

  13. 4, 21672238, 2004 Ozone loss and

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    ACPD 4, 2167­2238, 2004 Ozone loss and chlorine activation in the Arctic winters 1991­2003 S Union 2004 Atmospheric Chemistry and Physics Discussions Ozone loss and chlorine activation Correspondence to: S. Tilmes (simone.tilmes@t-online.de) 2167 #12;ACPD 4, 2167­2238, 2004 Ozone loss and chlorine

  14. Loss modeling for pricing catastrophic bonds 

    E-Print Network [OSTI]

    Sircar, Jyotirmoy

    2009-05-15

    loss model in the form of a power curve with upper and lower cut-offs is developed and used in conjunction with the previously defined demand model in order to estimate loss ratios. The loss model is calibrated and validated for different types...

  15. Stochastic Fermi Acceleration of sub-Relativistic Electrons and Its Role in Impulsive Solar Flares

    E-Print Network [OSTI]

    Robert Selkowitz; Eric G. Blackman

    2004-07-23

    We reexamine stochastic Fermi acceleration (STFA) in the low energy (Newtonian) regime in the context of solar flares. The particle energization rate depends a dispersive term and a coherent gain term. The energy dependence of pitch angle scattering is important for determining the electron energy spectrum. For scattering by whistler wave turbulence, STFA produces a quasi-thermal spectrum. A second well-constrained scattering mechanism is needed for STFA to match the observed 10-100keV non-thermal spectrum. We suggest that STFA most plausibly acts as phase one of a two phase particle acceleration engine in impulsive flares: STFA can match the thermal spectrum below 10kev, and possibly the power law spectrum between 10 and 100keV, given the proper pitch angle scattering. However, a second phase, such as shock acceleration at loop tops, is likely required to match the spectrum above the observed knee at 100keV. Understanding this knee, if it survives further observations, is tricky.

  16. Stochastic Fermi Acceleration of sub-Relativistic Electrons and Its Role in Impulsive Solar Flares

    E-Print Network [OSTI]

    Selkowitz, R; Selkowitz, Robert; Blackman, Eric G.

    2004-01-01

    We reexamine stochastic Fermi acceleration (STFA) in the low energy (Newtonian) regime in the context of solar flares. The particle energization rate depends a dispersive term and a coherent gain term. The energy dependence of pitch angle scattering is important for determining the electron energy spectrum. For scattering by whistler wave turbulence, STFA produces a quasi-thermal spectrum. A second well-constrained scattering mechanism is needed for STFA to match the observed 10-100keV non-thermal spectrum. We suggest that STFA most plausibly acts as phase one of a two phase particle acceleration engine in impulsive flares: STFA can match the thermal spectrum below 10kev, and possibly the power law spectrum between 10 and 100keV, given the proper pitch angle scattering. However, a second phase, such as shock acceleration at loop tops, is likely required to match the spectrum above the observed knee at 100keV. Understanding this knee, if it survives further observations, is tricky.

  17. Broadband Quasi-Periodic Radio and X-ray Pulsations in a Solar Flare

    E-Print Network [OSTI]

    G. D. Fleishman; T. S. Bastian; D. E. Gary

    2008-04-25

    We describe microwave and hard X-ray observations of strong quasiperiodic pulsations from the GOES X1.3 solar flare on 15 June 2003. The radio observations were made jointly by the Owens Valley Solar Array (OVSA), the Nobeyama Polarimeter (NoRP), and the Nobeyama Radioheliograph (NoRH). Hard X-ray observations were made by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Using Fourier analysis, we study the frequency- and energy-dependent oscillation periods, differential phase, and modulation amplitudes of the radio and X-ray pulsations. Focusing on the more complete radio observations, we also examine the modulation of the degree of circular polarization and of the radio spectral index. The observed properties of the oscillations are compared with those derived from two simple models for the radio emission. In particular, we explicitly fit the observed modulation amplitude data to the two competing models. The first model considers the effects of MHD oscillations on the radio emission. The second model considers the quasi-periodic injection of fast electrons. We demonstrate that quasiperiodic acceleration and injection of fast electrons is the more likely cause of the quasiperiodic oscillations observed in the radio and hard X-ray emission, which has important implications for particle acceleration and transport in the flaring sources.

  18. Magnetic structure and nonthermal electrons in the X6.9 flare on 2011 August 9

    SciTech Connect (OSTI)

    Hwangbo, Jung-Eun; Lee, Dae-Young [Department of Astronomy and Space Science, Chungbuk National University, Cheongju (Korea, Republic of); Lee, Jeongwoo [Physics Department, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Park, Sung-Hong; Kim, Sujin; Bong, Su-Chan; Kim, Yeon-Han; Cho, Kyung-Suk; Park, Young-Deuk [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)

    2014-12-01

    The 2011 August 9 flare is one of the largest X-ray flares of sunspot cycle 24, but spatial information is rather limited due to its position close to the western limb. This paper presents information about the location of high-energy electrons derived from hard X-ray and microwave spectra obtained with the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and the Korean Solar Radio Burst Locator (KSRBL), respectively. The KSRBL microwave spectrum shows significant fluxes at low frequencies, implying that the high-energy electrons reside in a coronal volume highly concentrated at strong magnetic fields, and rapidly expanding with decreasing magnetic fields. After a simple modeling of the microwave spectrum, we found that the microwave source should be located above the inner pair of magnetic poles in a large quadrupolar configuration. The time-dependent evolution of the magnetic field distribution and total nonthermal energy derived from the microwave spectra is also consistent with the standard picture of multiple magnetic reconnections recurring at a magnetic null point that forms above the magnetic quadrupoles and moves up with time.

  19. RESIK observations of He-like Ar X-ray line emission in solar flares

    E-Print Network [OSTI]

    J. Sylwester; B. Sylwester; K. J. H. Phillips

    2008-06-09

    The Ar XVII X-ray line group principally due to transitions 1s2 - 1s2l (l=s, p) near 4 Anstroms was observed in numerous flares by the RESIK bent crystal spectrometer aboard CORONAS-F between 2001 and 2003. The three line features include the Ar XVII w (resonance line), a blend of x and y (intercombination lines), and z (forbidden line), all of which are blended with Ar XVI dielectronic satellites. The ratio G, equal to [I(x+y) + I(z)]/I(w), varies with electron temperature Te mostly because of unresolved dielectronic satellites. With temperatures estimated from GOES X-ray emission, the observed G ratios agree fairly well with those calculated from CHIANTI and other data. With a two-component emission measure, better agreement is achieved. Some S XV and S XVI lines blend with the Ar lines, the effect of which occurs at temperatures greater than 8MK, allowing the S/Ar abundance ratio to be determined. This is found to agree with coronal values. A nonthermal contribution is indicated for some spectra in the repeating-pulse flare of 2003 February 6.

  20. Recovery Act: ArcelorMittal USA Blast Furnace Gas Flare Capture

    SciTech Connect (OSTI)

    Seaman, John

    2013-01-14

    The U.S. Department of Energy (DOE) awarded a financial assistance grant under the American Recovery and Reinvestment Act of 2009 (Recovery Act) to ArcelorMittal USA, Inc. (ArcelorMittal) for a project to construct and operate a blast furnace gas recovery boiler and supporting infrastructure at ArcelorMittal’s Indiana Harbor Steel Mill in East Chicago, Indiana. Blast furnace gas (BFG) is a by-product of blast furnaces that is generated when iron ore is reduced with coke to create metallic iron. BFG has a very low heating value, about 1/10th the heating value of natural gas. BFG is commonly used as a boiler fuel; however, before installation of the gas recovery boiler, ArcelorMittal flared 22 percent of the blast furnace gas produced at the No. 7 Blast Furnace at Indiana Harbor. The project uses the previously flared BFG to power a new high efficiency boiler which produces 350,000 pounds of steam per hour. The steam produced is used to drive existing turbines to generate electricity and for other requirements at the facility. The goals of the project included job creation and preservation, reduced energy consumption, reduced energy costs, environmental improvement, and sustainability.

  1. Evolution and Flare Activity of Delta-Sunspots in Cycle 23

    E-Print Network [OSTI]

    Takizawa, Kan

    2015-01-01

    The emergence and magnetic evolution of solar active regions (ARs) of beta-gamma-delta type, which are known to be highly flare-productive, were studied with the SOHO/MDI data in Cycle 23. We selected 31 ARs that can be observed from their birth phase, as unbiased samples for our study. From the analysis of the magnetic topology (twist and writhe), we obtained the following results. i) Emerging beta-gamma-delta ARs can be classified into three topological types as "quasi-beta", "writhed" and "top-to-top". ii) Among them, the "writhed" and "top-to-top" types tend to show high flare activity. iii) As the signs of twist and writhe agree with each other in most cases of the "writhed" type (12 cases out of 13), we propose a magnetic model in which the emerging flux regions in a beta-gamma-delta AR are not separated but united as a single structure below the solar surface. iv) Almost all the "writhed"-type ARs have downward knotted structures in the mid portion of the magnetic flux tube. This, we believe, is the es...

  2. Imaging and Spectral Observations of Quasi-Periodic Pulsations in a Solar Flare

    E-Print Network [OSTI]

    Li, D; Zhang, Q M

    2015-01-01

    We explore the Quasi-Periodic Pulsations (QPPs) in a solar flare observed by Fermi Gamma-ray Burst Monitor (GBM), Solar Dynamics Observatory (SDO), Solar Terrestrial Relations Observatory (STEREO), and Interface Region Imaging Spectrograph (IRIS) on 2014 September 10. QPPs are identified as the regular and periodic peaks on the rapidly-varying components, which are the light curves after removing the slowly-varying components. The QPPs display only three peaks at the beginning on the hard X-ray (HXR) emissions, but ten peaks on the chromospheric and coronal line emissions, and more than seven peaks (each peak is corresponding to a type III burst on the dynamic spectra) at the radio emissions. An uniform quasi-period about 4 minutes are detected among them. AIA imaging observations exhibit that the 4-min QPPs originate from the flare ribbon, and tend to appear on the ribbon front. IRIS spectral observations show that each peak of the QPPs tends to a broad line width and a red Doppler velocity at C I, O IV, Si ...

  3. Low-energy cutoffs in electron spectra of solar flares: statistical survey

    E-Print Network [OSTI]

    E. P. Kontar; E. Dickson; J. Kasparova

    2008-05-21

    The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) X-ray data base (February 2002 -- May 2006) has been searched to find solar flares with weak thermal components and flat photon spectra. Using a regularised inversion technique, we determine the mean electron flux distribution from count spectra of a selection of events with flat photon spectra in the 15--20 keV energy range. Such spectral behaviour is expected for photon spectra either affected by photospheric albedo or produced by electron spectra with an absence of electrons in a given energy range, e.g. a low-energy cutoff in the mean electron spectra of non-themal particles. We have found 18 cases which exhibit a statistically significant local minimum (a dip) in the range of 10--20 keV. The positions and spectral indices of events with low-energy cutoff indicate that such features are likely to be the result of photospheric albedo. It is shown that if the isotropic albedo correction was applied, all low-energy cutoffs in the mean electron spectrum were removed and hence the low energy cutoffs in the mean electron spectrum of solar flares above $\\sim$12 keV cannot be viewed as real features in the electron spectrum. If low-energy cutoffs exist in the mean electron spectra, the energy of low energy cutoffs should be less than $\\sim$12 keV.

  4. LOSS ANALYSIS OF BACK-CONTACT BACK-JUNCTION THIN-FILM MONOCRYSTALLINE SILICON SOLAR CELLS

    E-Print Network [OSTI]

    LOSS ANALYSIS OF BACK-CONTACT BACK-JUNCTION THIN-FILM MONOCRYSTALLINE SILICON SOLAR CELLS F. Haase losses in back-contact back- junction monocrystalline thin-film silicon solar cells. The cells are made for back-contact back- junction (BC BJ) monocrystalline thin-film silicon solar cells using the PSI process

  5. THE EFFECT OF A SELF-INDUCED ELECTRIC FIELD ON ELECTRON BEAM DIFFERENTIAL SPECTRA IN FLARING ATMOSPHERES

    E-Print Network [OSTI]

    Zharkova, Valentina V.

    THE EFFECT OF A SELF-INDUCED ELECTRIC FIELD ON ELECTRON BEAM DIFFERENTIAL SPECTRA IN FLARING field decrease with depth reduces the electron decelera- tion that allows beam electrons to precipitate. INTRODUCTION The effect of the induced electric field on the dynam- ics of non-thermal electron beams

  6. Physics of ion acceleration in the solar flare on 2005 September 7 determines c-ray and neutron production

    E-Print Network [OSTI]

    California at Berkeley, University of

    by the neutron monitors at Mt. Chacaltaya and Mexico City and by the solar neutron telescopes at ChacaltayaPhysics of ion acceleration in the solar flare on 2005 September 7 determines c-ray and neutron-sur-Yvette, France g Konan University, Nada-ku, Kobe 657-0000, Japan h Solar-Terrestrial Environment Laboratory

  7. A Two-ribbon White-light Flare Associated with a Failed Solar Eruption Observed by ONSET, SDO, and IRIS

    E-Print Network [OSTI]

    Cheng, X; Ding, M D; Liu, K; Chen, P F; Fang, C; Liu, Y D

    2015-01-01

    Two-ribbon brightenings are one of the most remarkable characteristics of an eruptive solar flare and are often used for predicting the occurrence of coronal mass ejections (CMEs). Nevertheless, it was called in question recently whether all two-ribbon flares are eruptive. In this paper, we investigate a two ribbon-like white-light (WL) flare that is associated with a failed magnetic flux rope (MFR) eruption on 2015 January 13, which has no accompanying CME in the WL coronagraph. Observations by \\textit{Optical and Near-infrared Solar Eruption Tracer} and \\textit{Solar Dynamics Observatory} reveal that, with the increase of the flare emission and the acceleration of the unsuccessfully erupting MFR, two isolated kernels appear at the WL 3600 {\\AA} passband and quickly develop into two elongated ribbon-like structures. The evolution of the WL continuum enhancement is completely coincident in time with the variation of \\textit{Fermi} hard X-ray 26--50 keV flux. Increase of continuum emission is also clearly visi...

  8. Statistics of X-ray flares of Sgr A*: evidence for solar-like self-organized criticality phenomenon

    E-Print Network [OSTI]

    Li, Ya-Ping; Yuan, Qiang; Wang, Q Daniel; Chen, P F; Neilsen, Joseph; Fang, Taotao; Zhang, Shuo; Dexter, Jason

    2015-01-01

    X-ray flares have routinely been observed from the supermassive black hole, Sgr A*, at our Galactic center. The nature of these flares remains largely unclear, despite of many theoretical models,. In this paper, we study the statistical properties of the Sgr A* X-ray flares, by fitting the count rate (CR) distribution and the structure function (SF) of the light curve with a Markov Chain Monte Carlo (MCMC) method. With the 3 million second \\textit{Chandra} observations accumulated in the Sgr A* X-ray Visionary Project, we construct the theoretical light curves through Monte Carlo simulations. We find that the $2-8$ keV X-ray light curve can be decomposed into a quiescent component with a constant count rate of $ 6\\times10^{-3} $count s$^{-1}$ and a flare component with a power-law fluence distribution $dN/dE\\propto E^{-\\alpha_{\\rm E}}$ with $\\alpha_{\\rm E}=1.65\\pm0.17$. The duration-fluence correlation can also be modelled as a power-law $T\\propto E^{\\alpha_{\\rm ET}}$ with $\\alpha_{\\rm ET} < 0.55$ ($95\\%$ ...

  9. An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles

    E-Print Network [OSTI]

    Grechnev, V V; Chertok, I M; Uralov, A M; Nakajima, H; Altyntsev, A T; Belov, A V; Yushkov, B Yu; Kuznetsov, S N; Kashapova, L K; Meshalkina, N S; Prestage, N P

    2008-01-01

    The extreme solar and SEP event of 20 January 2005 is analyzed from two perspectives. Firstly, we study features of the main phase of the flare, when the strongest emissions from microwaves up to 200 MeV gamma-rays were observed. Secondly, we relate our results to a long-standing controversy on the origin of SEPs arriving at Earth, i.e., acceleration in flares, or shocks ahead of CMEs. All emissions from microwaves up to 2.22 MeV line gamma-rays during the main flare phase originated within a compact structure located just above sunspot umbrae. A huge radio burst with a frequency maximum at 30 GHz was observed, indicating the presence of a large number of energetic electrons in strong magnetic fields. Thus, protons and electrons responsible for flare emissions during its main phase were accelerated within the magnetic field of the active region. The leading, impulsive parts of the GLE, and highest-energy gamma-rays identified with pi^0-decay emission, are similar and correspond in time. The origin of the pi^0...

  10. A close-up of the Sun (shown in ultraviolet light) reveals a mottled surface, bright flares,

    E-Print Network [OSTI]

    Christian, Eric

    #12;#12;A close-up of the Sun (shown in ultraviolet light) reveals a mottled surface, bright flares, and tongues of hot gas leaping into space. Though they look like burns in the face of the Sun, sunspots circle in the center of the photo--allows scientists to see the solar wind streaming away from the Sun

  11. First detection of >100 MeV gamma rays associated with a behind-the-limb solar flare

    E-Print Network [OSTI]

    Pesce-Rollins, Melissa; Petrosian, Vahe'; Liu, Wei; da Costa, Fatima Rubio; Allafort, Alice; Chen, Qingrong

    2015-01-01

    We report the first detection of >100 MeV gamma rays associated with a behind-the-limb solar flare, which presents a unique opportunity to probe the underlying physics of high-energy flare emission and particle acceleration. On 2013 October 11 a GOES M1.5 class solar flare occurred ~ 9.9 degrees behind the solar limb as observed by STEREO-B. RHESSI observed hard X-ray emission above the limb, most likely from the flare loop-top, as the footpoints were occulted. Surprisingly, the Fermi Large Area Telescope (LAT) detected >100 MeV gamma-rays for ~30 minutes with energies up to GeV. The LAT emission centroid is consistent with the RHESSI hard X-ray source, but its uncertainty does not constrain the source to be located there. The gamma-ray spectra can be adequately described by bremsstrahlung radiation from relativistic electrons having a relatively hard power-law spectrum with a high-energy exponential cutoff, or by the decay of pions produced by accelerated protons and ions with an isotropic pitch-angle distri...

  12. Near Infrared Observations at 1.56 m of the 2003 October 29 X10 White-Light Flare

    E-Print Network [OSTI]

    -infrared (NIR) continuum at 1.56 µm. This is the first report of a white-light flare observed in the NIR a newly developed high order adaptive optics (AO) system and a state-of-the-art NIR complex metal oxide) onboard the Solar and Heliospheric Observatory (SoHO) with the NIR continuum images. Since the NIR data

  13. PUBLISHED ONLINE: 15 AUGUST 2010 | DOI: 10.1038/NPHYS1741 The effect of flares on total solar irradiance

    E-Print Network [OSTI]

    Loss, Daniel

    from relatively moderate solar flares in total solar irradiance data. We find that the total energy, 4Solar Influences Data Analysis Centre / Royal Observatory of Belgium, Circular Avenue 3, B-1180 solar irradiance Matthieu Kretzschmar1 *, Thierry Dudok de Wit1 , Werner Schmutz2 , Sabri Mekaoui3

  14. Millimeter, Microwave, Hard X--ray and Soft X--ray Observations of Energetic Electron Populations in Solar Flares

    E-Print Network [OSTI]

    White, Stephen

    Millimeter, Microwave, Hard X--ray and Soft X--ray Observations of Energetic Electron Populations in Solar Flares M. R. Kundu 1 , S. M. White 1 , N. Gopalswamy 1 and J. Lim 1,2 1 Dept. of Astronomy, Univ. of Maryland, College Park MD 20742 2 Solar Astronomy 264--33, Caltech, Pasadena CA 91125 Submitted

  15. Stellar flares observed by LOFT: implications for the physics of coronae and for the "space weather" environment of extrasolar planets

    E-Print Network [OSTI]

    Drake, S A; Doyle, J G; Güdel, M; Hamaguchi, K; Kowalski, A F; Maccarone, T; Osten, R A; Peretz, U; Wolk, S J

    2015-01-01

    This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of stellar flares. For a summary, we refer to the paper.

  16. CAUSE AND EXTENT OF THE EXTREME RADIO FLUX DENSITY REACHED BY THE SOLAR FLARE OF 2006 DECEMBER 06

    E-Print Network [OSTI]

    are the reports of widespread effects on Global Positioning System (GPS) receivers. The potential for such effectsCAUSE AND EXTENT OF THE EXTREME RADIO FLUX DENSITY REACHED BY THE SOLAR FLARE OF 2006 DECEMBER 06 Dale E. Gary Center for Solar-Terrestrial Research, Physics Department, New Jersey Institute

  17. Minimize Boiler Short Cycling Losses | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Minimize Boiler Short Cycling Losses Minimize Boiler Short Cycling Losses This tip sheet on minimizing boiler short cycling losses provides how-to advice for improving industrial...

  18. Multilayer Platform for Ultra-Low-Loss Waveguide Applications

    E-Print Network [OSTI]

    2012-01-01

    1, 2012 Multilayer Platform for Ultra-Low-Loss Waveguidepreviously demonstrated ultra-low-loss technologies. Groupet al. : MULTILAYER PLATFORM FOR ULTRA-LOW-LOSS WAVEGUIDE

  19. Fe K emission and absorption features in XMM-Newton spectra of Mkn 766 - evidence for reprocessing in flare ejecta

    E-Print Network [OSTI]

    K. A. Pounds; J. N. Reeves; K. L. Page; G. A. Wynn; P. T. O'Brien

    2003-02-07

    We report on the analysis of a long XMM-Newton EPIC observation in 2001 May of the Narrow Line Seyfert 1 galaxy Mkn 766. The 3-11 keV spectrum exhibits a moderately steep power law continuum, with a broad emission line at ~6.7 keV, probably blended with a narrow line at ~6.4 keV, and a broad absorption trough above ~8.7 keV. We identify both broad spectral features with reprocessing in He-like Fe. An earlier XMM-Newton observation of Mkn 766 in 2000 May, when the source was a factor ~2 fainter, shows a similar broad emission line, but with a slightly flatter power law and absorption at a lower energy. In neither observation do we find a requirement for the previously reported broad 'red wing' to the line and hence of reflection from the innermost accretion disc. More detailed examination of the longer XMM-Newton observation reveals evidence for rapid spectral variability in the Fe K band, apparently linked with the occurrence of X-ray 'flares'. A reduction in the emission line strength and increased high energy absorption during the X-ray flaring suggests that these transient effects are due to highly ionised ejecta associated with the flares. Simple scaling from the flare avalanche model proposed for the luminous QSO PDS 456 (Reeves etal. 2002) confirms the feasibility of coherent flaring being the cause of the strong peaks seen in the X-ray light curve of \\mkn.

  20. Analysis of TPV Network Losses (a Presentation)

    SciTech Connect (OSTI)

    DM DePoy; MW Dashiell; DD Rahner; LR Danielson; JE Oppenlander; JL Vell; RJ Wehrer

    2004-12-08

    This talk focuses on the theoretical analysis of electrical losses associated with electrically networking large numbers of TPV cells to produce high power TPV power generators.

  1. Loan Loss Reserves: Lessons from the Field

    Broader source: Energy.gov [DOE]

    This webinar, held on Sept. 20, 2010, provides in formation on loan loss reserve funds and lessons from the field on their use.

  2. SIMULATION OF DESCENDING MULTIPLE SUPRA-ARCADE RECONNECTION OUTFLOWS IN SOLAR FLARES

    SciTech Connect (OSTI)

    Cecere, M.; Schneiter, M.; Costa, A.; Elaskar, S.; Maglione, S.

    2012-11-10

    After recent Atmospheric Imaging Assembly observations by Savage, McKenzie, and Reeves, we revisit the scenario proposed by us in previous papers. We have shown that sunward, generally dark plasma features that originated above posteruption flare arcades are consistent with a scenario where plasma voids (which we identify as supra-arcade reconnection outflows, SAROs) generate the bouncing and interfering of shocks and expansion waves upstream of an initial localized deposition of energy that is collimated in the magnetic field direction. In this paper, we analyze the multiple production and interaction of SAROs and their individual structures that make them relatively stable features while moving. We compare our results with observations and with the scenarios proposed by other authors.

  3. Tidal Disruption Flares as the Source of Ultra-high Energy Cosmic Rays

    E-Print Network [OSTI]

    Glennys R. Farrar

    2012-10-03

    The optical spectral energy distributions of two tidal disruption flares identified by van Velzen et al. (2011) in archival SDSS data, are found to be well-fit by a thin-accretion-disk model. Furthermore, the inferred Supermassive Black Hole mass values agree well with the SMBH masses estimated from the host galaxy properties. Integrating the model SEDs to include shorter wavelength contributions provides an estimate of the bolometric luminosities of the accretion disks. The resultant bolometric luminosities are well in excess of the minimum required for accelerating UHECR protons. In combination with the recent observational estimate of the TDF rate (van Velzen and Farrar, these Proceedings), the results presented here strengthen the case that transient jets formed in tidal disruption events may be responsible for accelerating all or most UHECRs.

  4. Tidal Disruption Flares as the Source of Ultra-high Energy Cosmic Rays

    E-Print Network [OSTI]

    Farrar, Glennys R

    2012-01-01

    The optical spectral energy distributions of two tidal disruption flares identified by van Velzen et al. (2011) in archival SDSS data, are found to be well-fit by a thin-accretion-disk model. Furthermore, the inferred Supermassive Black Hole mass values agree well with the SMBH masses estimated from the host galaxy properties. Integrating the model SEDs to include shorter wavelength contributions provides an estimate of the bolometric luminosities of the accretion disks. The resultant bolometric luminosities are well in excess of the minimum required for accelerating UHECR protons. In combination with the recent observational estimate of the TDF rate (van Velzen and Farrar, these Proceedings), the results presented here strengthen the case that transient jets formed in tidal disruption events may be responsible for accelerating all or most UHECRs.

  5. A scaled gradient projection method for the X-ray imaging of solar flares

    E-Print Network [OSTI]

    Bonettini, S

    2013-01-01

    In this paper we present a new optimization algorithm for the reconstruction of X-ray images of solar flares by means of the data collected by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The imaging concept of the satellite is based of rotating modulation collimator instruments, which allow the use of both Fourier imaging approaches and reconstruction techniques based on the straightforward inversion of the modulated count profiles. Although in the last decade a greater attention has been devoted to the former strategies due to their very limited computational cost, here we consider the latter model and investigate the effectiveness of a scaled gradient projection method for the solution of the corresponding constrained minimization problem. Moreover, regularization is introduced through either an early stopping of the iterative procedure, or a Tikhonov term added to the discrepancy function, by means of a discrepancy principle accounting for the Poisson nature of the noise affecting th...

  6. Astrophysical Explosions: From Solar Flares to Cosmic Gamma-ray Bursts

    E-Print Network [OSTI]

    Wheeler, J Craig

    2011-01-01

    Astrophysical explosions result from the release of magnetic, gravitational, or thermonuclear energy on dynamical timescales, typically the sound-crossing time for the system. These explosions include solar and stellar flares, eruptive phenomena in accretion disks, thermonuclear combustion on the surfaces of white dwarfs and neutron stars, violent magnetic reconnection in neutron stars, thermonuclear and gravitational collapse supernovae and cosmic gamma-ray bursts, each representing a different type and amount of energy release. This paper summarizes the properties of these explosions and describes new research on thermonuclear explosions and explosions in extended circumstellar media. Parallels are drawn between studies of terrestrial and astrophysical explosions, especially the physics of the transition from deflagration to detonation. Keywords: neutron stars, black holes, supernovae, gamma-ray bursts, deflagration, detonation.

  7. Modelling of Reflective Propagating Slow-mode Wave in a Flaring Loop

    E-Print Network [OSTI]

    Fang, X; Van Doorsselaere, T; Keppens, R; Xia, C

    2015-01-01

    Quasi-periodic propagating intensity disturbances have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. We perform a 2.5D magnetohydrodynamic simulation to imitate the chromospheric evaporation and the following reflected patterns in a flare loop. Our model encompasses the corona, transition region, and chromosphere. We demonstrate that the quasi periodic propagating intensity variations captured by the synthesized \\textit{Solar Dynamics Observatory}/Atmospheric Imaging Assembly (AIA) 131, 94~\\AA~emission images match the previous observations well. With particle tracers in the simulation, we confirm that these quasi periodic propagating intensity variations consist of reflected slow mode waves and mass flows with an average speed of 310 km/s in an 80 Mm length loop with an average temperatu...

  8. UFCORIN: A Fully Automated Predictor of Solar Flares in GOES X-Ray Flux

    E-Print Network [OSTI]

    Muranushi, Takayuki; Muranushi, Yuko Hada; Isobe, Hiroaki; Nemoto, Shigeru; Komazaki, Kenji; Shibata, Kazunari

    2015-01-01

    We have developed UFCORIN, a platform for studying and automating space weather prediction. Using our system we have tested 6,160 different combinations of SDO/HMI data as input data, and simulated the prediction of GOES X-ray flux for 2 years (2011-2012) with one-hour cadence. We have found that direct comparison of the true skill statistics (TSS) is ill-posed, and used the standard scores ($z$) of the TSS to compare the performance of the various prediction strategies. The best strategies we have found for predicting X, $\\geq$M and $\\geq$C class flares are better than the average of the 6,160 strategies by 2.3$\\sigma$, 2.1$\\sigma$, 3.8$\\sigma$ confidence levels, respectively. The best three's TSS values were $0.745\\pm0.072$, $0.481\\pm0.017$, and $0.557\\pm0.043$, respectively.

  9. Hard X-Ray Imaging of Individual Spectral Components in Solar Flares

    E-Print Network [OSTI]

    Caspi, Amir; McTiernan, James M; Krucker, Säm

    2015-01-01

    We present a new analytical technique, combining Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) high-resolution imaging and spectroscopic observations, to visualize solar flare emission as a function of spectral component (e.g., isothermal temperature) rather than energy. This computationally inexpensive technique is applicable to all spatially-invariant spectral forms and is useful for visualizing spectroscopically-determined individual sources and placing them in context, e.g., comparing multiple isothermal sources with nonthermal emission locations. For example, while extreme ultraviolet images can usually be closely identified with narrow temperature ranges, due to the emission being primarily from spectral lines of specific ion species, X-ray images are dominated by continuum emission and therefore have a broad temperature response, making it difficult to identify sources of specific temperatures regardless of the energy band of the image. We combine RHESSI calibrated X-ray visibilities wi...

  10. Faint Coronal Hard X-rays From Accelerated Electrons in Solar Flares

    E-Print Network [OSTI]

    Glesener, Lindsay Erin

    2012-01-01

    loss to jet kinetic and potential energies (dotted lines).and the jet kinetic and potential energies goes into heatinggoes into jet kinetic and potential energy, as discussed

  11. Corporate Energy Management Process 

    E-Print Network [OSTI]

    Geiger, T.

    2013-01-01

    Guideline 2000 Geismar Cogeneration ? AOG Fuel Utilization 2001 Freeport Cogeneration Project 2002 Portsmouth Site Energy Team 2003 Freeport ISBL Energy Audits 2004 Energy Management Group (EM) 2004 Geismar Flare Best Practice 2005 Site Energy...

  12. Loss characterization in microLoss characterization in micro--cavitiescavities using the thermalusing the thermal bistabilitybistability effecteffect

    E-Print Network [OSTI]

    Loss characterization in microLoss characterization in micro--cavitiescavities using Scattering limited Q #12;Quick Test for Loss CharacterizationQuick Test for Loss Characterization #12 to characterize different loss mechanisms in these structuresdifferent loss mechanisms in these structures nn

  13. Modeling particle loss in ventilation ducts

    SciTech Connect (OSTI)

    Sippola, Mark R.; Nazaroff, William W.

    2003-04-01

    Empirical equations were developed and applied to predict losses of 0.01-100 {micro}m airborne particles making a single pass through 120 different ventilation duct runs typical of those found in mid-sized office buildings. For all duct runs, losses were negligible for submicron particles and nearly complete for particles larger than 50 {micro}m. The 50th percentile cut-point diameters were 15 {micro}m in supply runs and 25 {micro}m in return runs. Losses in supply duct runs were higher than in return duct runs, mostly because internal insulation was present in portions of supply duct runs, but absent from return duct runs. Single-pass equations for particle loss in duct runs were combined with models for predicting ventilation system filtration efficiency and particle deposition to indoor surfaces to evaluate the fates of particles of indoor and outdoor origin in an archetypal mechanically ventilated building. Results suggest that duct losses are a minor influence for determining indoor concentrations for most particle sizes. Losses in ducts were of a comparable magnitude to indoor surface losses for most particle sizes. For outdoor air drawn into an unfiltered ventilation system, most particles smaller than 1 {micro}m are exhausted from the building. Large particles deposit within the building, mostly in supply ducts or on indoor surfaces. When filters are present, most particles are either filtered or exhausted. The fates of particles generated indoors follow similar trends as outdoor particles drawn into the building.

  14. Excessive loss of information by the power-law ansatz for complex systems

    E-Print Network [OSTI]

    Tsai, Sun-Ting; Chang, Ching-Hao; Tsai, Meng-Xue; Hsu, Nan-Jung; Hong, Tzay-Ming

    2015-01-01

    Physicists love simple laws and uncovering common causes among seemingly unrelated phenomena. An example is the connection between earthquakes and crumpling of a paper, built through the simple power law (SPL) believed to exist between the occurrence rate of their crackling noise and the pulse intensity. We provide, however, evidence to weaken such a link by showing that both systems in fact obey different and more complex laws. Our analyses are based on the Akaike information criterion (AIC) that is a direct measurement of information loss and emphasizes the need to strike a balance between model simplicity and goodness of fit. AIC found that a shifted power law retains more information than SPL in the cases of crumpling sound, duration-time frequency of solar flare, web link, protein-domain frequency, and stock-market fluctuations. In the mean time, double power laws (DPL) should replace the Gutenberg-Richter law for earthquake, and the scale-free model for brain functional network, two-dimensional sandpile...

  15. Variation of the broad X-ray iron line in MCG-6-30-15 during a flare

    E-Print Network [OSTI]

    K. Iwasawa; A. C. Fabian; A. J. Young; H. Inoue; C. Matsumoto

    1999-04-07

    We report results on the broad iron emission line of the Seyfert galaxy MCG-6-30-15, obtained from the second long ASCA observation in 1997. The time-averaged profile of the broad line is very similar to that seen with ASCA in 1994, so confirming the detailed model fit then obtained. A bright flare is seen in the light curve, during which the continuum was soft. At that time the emission line peaks around 5 keV and most of its emission is shifted below 6 keV with no component detected at 6.4 keV (EW<60 eV). This can be interpreted as the result of an extraordinarily large gravitational redshift due to a dominant flare occurring very close to the black hole at a radius of <5m.

  16. XMM-Newton observations of SGR 1806-20 over seven years following the 2004 Giant Flare

    E-Print Network [OSTI]

    Younes, G; Kaspi, V M

    2015-01-01

    We report on the study of 14 XMM-Newton observations of the magnetar SGR 1806-20 spread over a period of 8 years, starting in 2003 and extending to 2011. We find that in mid 2005, a year and a half after a giant flare (GF), the torques on the star increased to the largest value yet seen, with a long term average rate between 2005 and 2011 of $\\lvert\\dot{\

  17. Compton backscattered and primary X-rays from solar flares: angle dependent Green's function correction for photospheric albedo

    E-Print Network [OSTI]

    Eduard P. Kontar; Alec L. MacKinnon; Richard A. Schwartz; John C. Brown

    2005-10-06

    The observed hard X-ray (HXR) flux spectrum $I(\\epsilon)$ from solar flares is a combination of primary bremsstrahlung photons $I_P(\\epsilon)$ with a spectrally modified component from photospheric Compton backscatter of downward primary emission. The latter can be significant, distorting or hiding the true features of the primary spectrum which are key diagnostics for acceleration and propagation of high energy electrons and of their energy budget. For the first time in solar physics, we use a Green's function approach to the backscatter spectral deconvolution problem, constructing a Green's matrix including photoelectric absorption. This approach allows spectrum-independent extraction of the primary spectrum for several HXR flares observed by the {\\it Ramaty High Energy Solar Spectroscopic Imager} (RHESSI). We show that the observed and primary spectra differ very substantially for flares with hard spectra close to the disk centre. We show in particular that the energy dependent photon spectral index $\\gamma (\\epsilon)=-d \\log I/d \\log \\epsilon$ is very different for $I_P(\\epsilon)$ and for $I(\\epsilon)$ and that inferred mean source electron spectra ${\\bar F}(E)$ differ greatly. Even for a forward fitting of a parametric ${\\bar F}(E)$ to the data, a clear low-energy cutoff required to fit $I(\\epsilon)$ essentially disappears when the fit is to $I_P(\\epsilon)$ - i.e. when albedo correction is included. The self-consistent correction for backscattered photons is thus shown to be crucial in determining the energy spectra of flare accelerated electrons, and hence their total number and energy.

  18. Optimization of quantum interferometric metrological sensors in the presence of photon loss

    E-Print Network [OSTI]

    Tae-Woo Lee; Sean D. Huver; Hwang Lee; Lev Kaplan; Steven B. McCracken; Changjun Min; Dmitry B. Uskov; Christoph F. Wildfeuer; Georgios Veronis; Jonathan P. Dowling

    2009-08-20

    We optimize two-mode, entangled, number states of light in the presence of loss in order to maximize the extraction of the available phase information in an interferometer. Our approach optimizes over the entire available input Hilbert space with no constraints, other than fixed total initial photon number. We optimize to maximize the Fisher information, which is equivalent to minimizing the phase uncertainty. We find that in the limit of zero loss the optimal state is the so-called N00N state, for small loss, the optimal state gradually deviates from the N00N state, and in the limit of large loss the optimal state converges to a generalized two-mode coherent state, with a finite total number of photons. The results provide a general protocol for optimizing the performance of a quantum optical interferometer in the presence of photon loss, with applications to quantum imaging, metrology, sensing, and information processing.

  19. Measurement of the mechanical loss of a cooled reflective coating for gravitational wave detection

    E-Print Network [OSTI]

    Kazuhiro Yamamoto; Shinji Miyoki; Takashi Uchiyama; Hideki Ishitsuka; Masatake Ohashi; Kazuaki Kuroda; Takayuki Tomaru; Nobuaki Sato; Toshikazu Suzuki; Tomiyoshi Haruyama; Akira Yamamoto; Takakazu Shintomi; Kenji Numata; Koichi Waseda; Kazuhiko Ito; Koji Watanabe

    2006-07-22

    We have measured the mechanical loss of a dielectric multilayer reflective coating (ion-beam sputtered SiO$_2$ and Ta$_2$O$_5$) in cooled mirrors. The loss was nearly independent of the temperature (4 K $\\sim$ 300 K), frequency, optical loss, and stress caused by the coating, and the details of the manufacturing processes. The loss angle was $(4 \\sim 6) \\times 10^{-4}$. The temperature independence of this loss implies that the amplitude of the coating thermal noise, which is a severe limit in any precise measurement, is proportional to the square root of the temperature. Sapphire mirrors at 20 K satisfy the requirement concerning the thermal noise of even future interferometric gravitational wave detector projects on the ground, for example, LCGT.

  20. Internal energy dissipation of gamma-ray bursts observed with Swift: Precursors, prompt gamma-rays, extended emission, and late X-ray flares

    SciTech Connect (OSTI)

    Hu, You-Dong; Liang, En-Wei; Xi, Shao-Qiang; Peng, Fang-Kun; Lu, Rui-Jing; Lü, Lian-Zhong [Department of Physics and GXU-NAOC Center for Astrophysics and Space Sciences, Guangxi University, Nanning 530004 (China); Zhang, Bing, E-mail: lew@gxu.edu.cn, E-mail: Zhang@physics.unlv.edu [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

    2014-07-10

    We jointly analyze the gamma-ray burst (GRB) data observed with Burst Alert Telescope (BAT) and X-ray Telescope on board the Swift mission to present a global view on the internal energy dissipation processes in GRBs, including precursors, prompt gamma-ray emission, extended soft gamma-ray emission, and late X-ray flares. The Bayesian block method is utilized to analyze the BAT light curves to identify various emission episodes. Our results suggest that these emission components likely share the same physical origin, which is the repeated activation of the GRB central engine. What we observe in the gamma-ray band may be a small part of more extended underlying activities. The precursor emission, which is detected in about 10% of Swift GRBs, is preferably detected in those GRBs that have a massive star core-collapse origin. The soft extended emission tail, on the other hand, is preferably detected in those GRBs that have a compact star merger origin. Bright X-ray emission is detected during the BAT quiescent phases prior to subsequent gamma-ray peaks, implying that X-ray emission may be detectable prior the BAT trigger time. Future GRB alert instruments with soft X-ray capability are essential for revealing the early stages of GRB central engine activities, and shedding light on jet composition and the jet launching mechanism in GRBs.

  1. Hydrogen H$?$ line polarization in solar flares. Theoretical investigation of atomic polarization by proton beams considering self-consistent NLTE polarized radiative transfer

    E-Print Network [OSTI]

    Jiri Stepan; Petr Heinzel; Sylvie Sahal-Brechot

    2007-01-22

    Context. We present a theoretical review of the effect of impact polarization of a hydrogen H$\\alpha$ line due to an expected proton beam bombardment in solar flares. Aims. Several observations indicate the presence of the linear polarization of the hydrogen H$\\alpha$ line observed near the solar limb above 5% and preferentially in the radial direction. We theoretically review the problem of deceleration of the beam originating in the coronal reconnection site due to its interaction with the chromospheric plasma, and describe the formalism of the density matrix used in our description of the atomic processes and the treatment of collisional rates. Methods. We solve the self-consistent NLTE radiation transfer problem for the particular semiempirical chromosphere models for both intensity and linear polarization components of the radiation field. Results. In contrast to recent calculations, our results show that the energy distribution of the proton beam at H$\\alpha$ formation levels and depolarizing collisions by background electrons and protons cause a significant reduction of the effect below 0.1%. The radiation transfer solution shows that tangential resonance-scattering polarization dominates over the impact polarization effect in all considered models. Conclusions. In the models studied, proton beams are unlikely to be a satisfying explanation for the observed linear polarization of the H$\\alpha$ line.

  2. Study of the properties of Cosmic rays and solar X-Ray Flares by balloon borne experiments

    E-Print Network [OSTI]

    Chakrabarti, S K; Chakraborty, S; Palit, S; Mondal, S K; Bhattacharya, A; Midya, S; Chakrabarti, S

    2013-01-01

    Indian Centre for Space Physics is engaged in pioneering balloon borne experiments with typical payloads less than ~ 3.5kg. Low cost rubber balloons are used to fly them to a height of about 40km. In a double balloon system, the booster balloon lifts the orbiter balloon to its cruising altitude where data is taken for a longer period of time. In this Paper, we present our first scientific report on the variation of Cosmic Rays and muons with altitude and detection of several solar flares in X-rays between 20keV and 100keV. We found the altitude of the Pfotzer maximum at Tropic of Cancer for cosmic rays and muons and catch several solar flares in hard X-rays. We find that the hard X-ray (> 40keV) sky becomes very transparent above Pfotzer maximum. We find the flare spectrum to have a power-law distribution. From these studies, we infer that valuable scientific research could be carried out in near space using low cost balloon borne experiments. Published in Online version of Indian Journal of Physics.

  3. Destabilization of a Solar Prominence/Filament Field System by a Series of Eight Homologous Eruptive Flares

    E-Print Network [OSTI]

    Panesar, Navdeep K; Innes, Davina E; Moore, Ronald L

    2015-01-01

    Homologous flares are flares that occur repetitively in the same active region, with similar structure and morphology. A series of at least eight homologous flares occurred in active region NOAA 11237 over 16 - 17 June 2011. A nearby prominence/filament was rooted in the active region, and situated near the bottom of a coronal cavity. The active region was on the southeast solar limb as seen from SDO/AIA, and on the disk as viewed from STEREO/EUVI-B. The dual perspective allows us to study in detail behavior of the prominence/filament material entrained in the magnetic field of the repeatedly-erupting system. Each of the eruptions was mainly confined, but expelled hot material into the prominence/filament cavity system (PFCS). The field carrying and containing the ejected hot material interacted with the PFCS and caused it to inflate, resulting in a step-wise rise of the PFCS approximately in step with the homologous eruptions. The eighth eruption triggered the PFCS to move outward slowly, accompanied by a we...

  4. Observation of 2011-02-15 X2.2 flare in Hard X-ray and Microwave

    E-Print Network [OSTI]

    Kuroda, Natsuha; Gary, Dale E

    2015-01-01

    Previous studies have shown that the energy release mechanism of some solar flares follow the Standard magnetic-reconnection model, but the detailed properties of high-energy electrons produced in the flare are still not well understood. We conducted a unique, multi-wavelength study that discloses the spatial, temporal and energy distributions of the accelerated electrons in the X2.2 solar flare on 2011, Feb. 15. We studied the source locations of seven distinct temporal peaks observed in hard X-ray (HXR) and microwave (MW) lightcurves using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in 50 to 75 keV channels and Nobeyama Radioheliograph (NoRH) in 34 GHz, respectively. We found that the seven emission peaks did not come from seven spatially distinct sites in HXR and MW, but rather in HXR we observed a sudden change in location only between the second and the third peak, with the same pattern occurring, but evolving more slowly in MW. Comparison between the HXR lightcurve and the temporal...

  5. Telling Absence: War Widows, Loss and Memory 

    E-Print Network [OSTI]

    Loipponen, Jaana

    2009-01-01

    This thesis concerns feminist sociological analysis of war loss and its consequences as experienced and told by Finnish Karelian war widows of World War 2. They lost their partners and had to leave their homes by force, ...

  6. High temperature elemental losses and mineralogical

    E-Print Network [OSTI]

    Thy, P.; Jenkins, B. M.; Grundvig, S.; Shiraki, R.; Lesher, C. E.

    2006-01-01

    ashes. The K 2 O loss for wood ash commences at 900–1000 8C.Carbonate is detected in the wood ashes to about 700–800 8Cphases detected in the wood ashes (pericline and larnite)

  7. Assessing Phosphorous Loss to Protect Surface Water 

    E-Print Network [OSTI]

    Garcia, Raul

    2005-01-01

    programs. It is an integrated approach that considers soil and landscape features in order tx H2O | pg. 10 Assessing Phosphorus Loss to Protect Surface Water to find appropriate phosphorus management practices by estimating phosphorus delivery...

  8. PHYSICAL PROCESSES SHAPING GAMMA-RAY BURST X-RAY AFTERGLOW LIGHT CURVES: THEORETICAL IMPLICATIONS FROM THE SWIFT X-RAY TELESCOPE OBSERVATIONS

    E-Print Network [OSTI]

    Zhang, Bing

    PHYSICAL PROCESSES SHAPING GAMMA-RAY BURST X-RAY AFTERGLOW LIGHT CURVES: THEORETICAL IMPLICATIONS August 15; accepted 2005 December 19 ABSTRACT With the successful launch of the Swift Gamma-Ray Burst component is consistent with the tail emission of the prompt gamma-ray bursts and/or the X-ray flares

  9. A Systematic Study of X-Ray Flares from Low-Mass Young Stellar Objects in the Rho Ophiuchi Star-Forming Region with Chandra

    E-Print Network [OSTI]

    K. Imanishi; H. Nakajima; M. Tsujimoto; K. Koyama; Y. Tsuboi

    2003-05-10

    We report on the results of a systematic study of X-ray flares from low-mass young stellar objects, using Chandra observations of the main region of the Rho Oph. From 195 X-ray sources, including class I-III sources and some young brown dwarfs, we detected a total of 71 X-ray flares. Most of the flares have the typical profile of solar and stellar flares, fast rise and slow decay. We derived the time-averaged temperature (kT), luminosity (L_X), rise and decay timescales (tau_r and tau_d) of the flares, finding that (1) class I-II sources tend to have a high kT, (2) the distribution of L_X during flares is nearly the same for all classes, and (3) positive and negative log-linear correlations are found between tau_r and tau_d, and kT and tau_r. In order to explain these relations, we used the framework of magnetic reconnection model to formulate the observational parameters as a function of the half-length of the reconnected magnetic loop (L) and magnetic field strength (B). The estimated L is comparable to the typical stellar radius of these objects (10^{10-11} cm), which indicates that the observed flares are triggered by solar-type loops, rather than larger ones (10^{12} cm) connecting the star with its inner accretion disk. The higher kT observed for class I sources may be explained by a higher magnetic field strength (about 500 G) than for class II-III sources (200-300 G).

  10. RAPID ENHANCEMENT OF SHEARED EVERSHED FLOW ALONG THE NEUTRAL LINE ASSOCIATED WITH AN X6.5 FLARE OBSERVED BY HINODE

    SciTech Connect (OSTI)

    Deng Na; Choudhary, Debi Prasad; Liu Chang; Wang Haimin E-mail: debiprasad.choudhary@csun.edu E-mail: haimin@flare.njit.edu

    2011-05-20

    We present G-band and Ca II H observations of NOAA AR 10930 obtained by Hinode/SOT on 2006 December 6 covering an X6.5 flare. The Local Correlation Tracking technique was applied to the foreshortening-corrected G-band image series to acquire horizontal proper motions in this complex {beta}{gamma}{delta} active region. With the continuous high-quality, spatial and temporal resolution G-band data, we not only confirm the rapid decay of outer penumbrae and darkening of the central structure near the flaring neutral line, but also unambiguously detect for the first time the enhancement of the sheared Evershed flow (average horizontal flow speed increased from 330 {+-} 3.1 to 403 {+-} 4.6 m s{sup -1}) along the neutral line right after the eruptive white-light flare. Post-flare Ca II H images indicate that the originally fanning out field lines at the two sides of the neutral line get connected. Since penumbral structure and Evershed flow are closely related to photospheric magnetic inclination or horizontal field strength, we interpret the rapid changes of sunspot structure and surface flow as the result of flare-induced magnetic restructuring down to the photosphere. The magnetic fields turn from fanning out to inward connection causing outer penumbrae decay, meanwhile those near the flaring neutral line become more horizontal leading to stronger Evershed flow there. The inferred enhancement of horizontal magnetic field near the neutral line is consistent with recent magnetic observations and theoretical predictions of flare-invoked photospheric magnetic field change.

  11. Dynamics of double layers, ion acceleration, and heat flux suppression during solar flares

    SciTech Connect (OSTI)

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2014-09-20

    Observations of flare-heated electrons in the corona typically suggest confinement of electrons. The confinement mechanism, however, remains unclear. The transport of coronal hot electrons into ambient plasma was recently investigated by particle-in-cell (PIC) simulations. Electron transport was significantly suppressed by the formation of a highly localized, nonlinear electrostatic potential in the form of a double layer (DL). In this work large-scale PIC simulations are performed to explore the dynamics of DLs in larger systems where, instead of a single DL, multiple DLs are generated. The primary DL accelerates return current electrons, resulting in high velocity electron beams that interact with ambient ions. This forms a Buneman unstable system that spawns more DLs. Trapping of heated return current electrons between multiple DLs strongly suppresses electron transport. DLs also accelerate ambient ions and produce strong ion flows over an extended region. This clarifies the mechanism by which hot electrons in the corona couple to and accelerate ions to form the solar wind. These new dynamics in larger systems reveal a more likely picture of DL development and their impact on the ambient plasma in the solar corona. They are applicable to the preparation for in situ coronal space missions like the Solar Probe Plus.

  12. On the variation of solar flare coronal X-ray source sizes with energy

    SciTech Connect (OSTI)

    Jeffrey, Natasha L. S.; Kontar, Eduard P.; Bian, Nicolas H. [School of Physics and Astronomy, University of Glasgow, G12 8QQ Glasgow (United Kingdom); Emslie, A. Gordon, E-mail: n.jeffrey@physics.gla.ac.uk [Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)

    2014-05-20

    Observations with RHESSI have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of non-thermal particles in a one-dimensional cold target model and the results used to constrain both the physical extent of, and density within, the electron acceleration region. Here, we extend this investigation to a more physically realistic model of electron transport that takes into account the finite temperature of the ambient plasma, the initial pitch angle distribution of the accelerated electrons, and the effects of collisional pitch angle scattering. The finite temperature results in the thermal diffusion of electrons, which leads to the observationally inferred value of the acceleration region volume being an overestimate of its true value. The different directions of the electron trajectories, a consequence of both the non-zero injection pitch angle and scattering within the target, cause the projected propagation distance parallel to the guiding magnetic field to be reduced, so that a one-dimensional interpretation can overestimate the actual density by a factor of up to ?6. The implications of these results for the determination of acceleration region properties (specific acceleration rate, filling factor, etc.) are discussed.

  13. KAPPA DISTRIBUTION MODEL FOR HARD X-RAY CORONAL SOURCES OF SOLAR FLARES

    SciTech Connect (OSTI)

    Oka, M.; Ishikawa, S.; Saint-Hilaire, P.; Krucker, S.; Lin, R. P. [Space Sciences Laboratory, University of California Berkeley (United States)] [Space Sciences Laboratory, University of California Berkeley (United States)

    2013-02-10

    Solar flares produce hard X-ray emission, the photon spectrum of which is often represented by a combination of thermal and power-law distributions. However, the estimates of the number and total energy of non-thermal electrons are sensitive to the determination of the power-law cutoff energy. Here, we revisit an 'above-the-loop' coronal source observed by RHESSI on 2007 December 31 and show that a kappa distribution model can also be used to fit its spectrum. Because the kappa distribution has a Maxwellian-like core in addition to a high-energy power-law tail, the emission measure and temperature of the instantaneous electrons can be derived without assuming the cutoff energy. Moreover, the non-thermal fractions of electron number/energy densities can be uniquely estimated because they are functions of only the power-law index. With the kappa distribution model, we estimated that the total electron density of the coronal source region was {approx}2.4 Multiplication-Sign 10{sup 10} cm{sup -3}. We also estimated without assuming the source volume that a moderate fraction ({approx}20%) of electrons in the source region was non-thermal and carried {approx}52% of the total electron energy. The temperature was 28 MK, and the power-law index {delta} of the electron density distribution was -4.3. These results are compared to the conventional power-law models with and without a thermal core component.

  14. Swift J1112.2-8238: A Candidate Relativistic Tidal Disruption Flare

    E-Print Network [OSTI]

    Brown, G C; Stanway, E R; Tanvir, N R; Cenko, S B; Berger, E; Chornock, R; Cucchiaria, A

    2015-01-01

    We present observations of Swift J1112.2-8238, and identify it as a candidate relativistic tidal disruption flare (rTDF). The outburst was first detected by Swift/BAT in June 2011 as an unknown, long-lived (order of days) $\\gamma$-ray transient source. We show that its position is consistent with the nucleus of a faint galaxy for which we establish a likely redshift of $z=0.89$ based on a single emission line that we interpret as the blended [OII]$\\lambda3727$ doublet. At this redshift, the peak X/$\\gamma$-ray luminosity exceeded $10^{47}$ ergs s$^{-1}$, while a spatially coincident optical transient source had $i^{\\prime} \\sim 22$ (M$_g \\sim -21.4$ at $z=0.89$) during early observations, $\\sim 20$ days after the Swift trigger. These properties place Swift J1112.2-8238 in a very similar region of parameter space to the two previously identified members of this class, Swift J1644+57 and Swift J2058+0516. As with those events the high-energy emission shows evidence for variability over the first few days, while...

  15. The formation of kappa-distribution accelerated electron populations in solar flares

    SciTech Connect (OSTI)

    Bian, Nicolas H.; Stackhouse, Duncan J.; Kontar, Eduard P. [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Emslie, A. Gordon, E-mail: n.bian@physics.gla.ac.uk, E-mail: d.stackhouse.1@research.gla.ac.uk, E-mail: eduard@astro.gla.ac.uk, E-mail: emslieg@wku.edu [Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)

    2014-12-01

    Driven by recent RHESSI observations of confined loop-top hard X-ray sources in solar flares, we consider stochastic acceleration of electrons in the presence of Coulomb collisions. If electron escape from the acceleration region can be neglected, the electron distribution function is determined by a balance between diffusive acceleration and collisions. Such a scenario admits a stationary solution for the electron distribution function that takes the form of a kappa distribution. We show that the evolution toward this kappa distribution involves a 'wave front' propagating forward in velocity space, so that electrons of higher energy are accelerated later; the acceleration timescales with energy according to ?{sub acc} ? E {sup 3/2}. At sufficiently high energies escape from the finite-length acceleration region will eventually dominate. For such energies, the electron velocity distribution function is obtained by solving a time-dependent Fokker-Planck equation in the 'leaky-box' approximation. Solutions are obtained in the limit of a small escape rate from an acceleration region that can effectively be considered a thick target.

  16. Bulk Energization of Electrons in Solar Flares by Alfv\\'en Waves

    E-Print Network [OSTI]

    Melrose, D B

    2013-01-01

    Bulk energization of electrons to $10\\,-\\,20\\,$keV in solar flares is attributed to dissipation of Alfv\\'en waves that transport energy and potential downward to an acceleration region near the chromosphere. The acceleration involves the parallel electric field that develops in the limit of inertial Alfv\\'en waves (IAWs). A two-potential model for IAWs is used to relate the parallel potential to the cross-field potential transported by the waves. We identify a maximum parallel potential in terms of a maximum current density that corresponds to the threshold for the onset of anomalous resistivity. This maximum is of order $10\\,$kV when the threshold is that for the Buneman instability. We argue that this restricts the cross-field potential in an Alfv\\'en wave to about $10\\,$kV. Effective dissipation requires a large number of up- and down-current paths associated with multiple Alfv\\'en waves. The electron acceleration occurs in localized, transient, anomalously-conducting regions (LTACRs) and is associated wit...

  17. On the variation of solar flare coronal x-ray source sizes with energy

    E-Print Network [OSTI]

    Jeffrey, Natasha L S; Bian, Nicolas H; Emslie, A Gordon

    2014-01-01

    Observations with {\\em RHESSI} have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of non-thermal particles in a one-dimensional cold-target model, and the results used to constrain both the physical extent of, and density within, the electron acceleration region. Here we extend this investigation to a more physically realistic model of electron transport that takes into account the finite temperature of the ambient plasma, the initial pitch-angle distribution of the accelerated electrons, and the effects of collisional pitch-angle scattering. The finite temperature results in the thermal diffusion of electrons, that leads to the observationally-inferred value of the acceleration region volume being an overestimate of its true value. The different directions of the electron trajectories, a consequence of both the non-zero injection pitch-angle and scattering with...

  18. Optical polarization map of the Polaris Flare with RoboPol

    E-Print Network [OSTI]

    Panopoulou, G V; Blinov, D; Pavlidou, V; King, O G; Paleologou, E; Ramaprakash, A; Angelakis, E; Balokovic, M; Das, H K; Feiler, R; Hovatta, T; Khodade, P; Kiehlmann, S; Kus, A; Kylafis, N; Liodakis, I; Modi, D; Myserlis, I; Papadakis, I; Papamastorakis, I; Pazderska, B; Pazderski, E; Pearson, T J; Rajarshi, C; Readhead, A C S; Reig, P; Zensus, J A

    2015-01-01

    The stages before the formation of stars in molecular clouds are poorly understood. Insights can be gained by studying the properties of quiescent clouds, such as their magnetic field structure. The plane-of-the-sky orientation of the field can be traced by polarized starlight. We present the first extended, wide-field ($\\sim$10 $\\rm deg^2$) map of the Polaris Flare cloud in dust-absorption induced optical polarization of background stars, using the RoboPol polarimeter at the Skinakas Observatory. This is the first application of the wide-field imaging capabilities of RoboPol. The data were taken in the R-band and analysed with the automated reduction pipeline of the instrument. We present in detail optimizations in the reduction pipeline specific to wide-field observations. Our analysis resulted in reliable measurements of 648 stars with median fractional linear polarization 1.3%. The projected magnetic field shows a large scale ordered pattern. At high longitudes it appears to align with faint striations se...

  19. Measurements and Modeling of Total Solar Irradiance in X-Class Solar Flares

    E-Print Network [OSTI]

    Moore, Christopher Samuel; Hock, Rachel

    2015-01-01

    The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment (SORCE) can detect changes in the Total Solar Irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-Class solar ares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar ares presented in Woods et al. (2006), as well as an additional are measured on 2006 December 6. The radiative outputs for both phases of these five ares are then compared to the Vacuum Ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-Class ares. This model provides the basis for the bolometric energy estimates for the solar ares analyzed in the Emslie et al. (2012) study.

  20. Triggering an eruptive flare by emerging flux in a solar active-region complex

    E-Print Network [OSTI]

    Louis, Rohan E; Ravindra, B; Chintzoglou, Georgios

    2015-01-01

    A flare and fast coronal mass ejection originated between solar active regions NOAA 11514 and 11515 on July 1, 2012 in response to flux emergence in front of the leading sunspot of the trailing region 11515. Analyzing the evolution of the photospheric magnetic flux and the coronal structure, we find that the flux emergence triggered the eruption by interaction with overlying flux in a non-standard way. The new flux neither had the opposite orientation nor a location near the polarity inversion line, which are favorable for strong reconnection with the arcade flux under which it emerged. Moreover, its flux content remained significantly smaller than that of the arcade (approximately 40 %). However, a loop system rooted in the trailing active region ran in part under the arcade between the active regions, passing over the site of flux emergence. The reconnection with the emerging flux, leading to a series of jet emissions into the loop system, caused a strong but confined rise of the loop system. This lifted th...