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Title: CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITH IRIS AND EIS

Abstract

Chromospheric evaporation refers to dynamic mass motions in flare loops as a result of rapid energy deposition in the chromosphere. These motions have been observed as blueshifts in X-ray and extreme-ultraviolet (EUV) spectral lines corresponding to upward motions at a few tens to a few hundreds of km s{sup −1}. Past spectroscopic observations have also revealed a dominant stationary component, in addition to the blueshifted component, in emission lines formed at high temperatures (∼10 MK). This is contradictory to evaporation models predicting predominant blueshifts in hot lines. The recently launched Interface Region Imaging Spectrograph (IRIS) provides high-resolution imaging and spectroscopic observations that focus on the chromosphere and transition region in the UV passband. Using the new IRIS observations, combined with coordinated observations from the EUV Imaging Spectrometer, we study the chromospheric evaporation process from the upper chromosphere to the corona during an X1.0 flare on 2014 March 29. We find evident evaporation signatures, characterized by Doppler shifts and line broadening, at two flare ribbons that are separating from each other, suggesting that chromospheric evaporation takes place in successively formed flaring loops throughout the flare. More importantly, we detect dominant blueshifts in the high-temperature Fe xxi line (∼10 MK), in agreementmore » with theoretical predictions. We also find that, in this flare, gentle evaporation occurs at some locations in the rise phase of the flare, while explosive evaporation is detected at some other locations near the peak of the flare. There is a conversion from gentle to explosive evaporation as the flare evolves.« less

Authors:
;  [1];  [2];  [3]
  1. School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)
  2. Department of Physics, Montana State University, Bozeman, MT 59717 (United States)
  3. Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China)
Publication Date:
OSTI Identifier:
22525431
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 811; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHROMOSPHERE; DOPPLER EFFECT; ENERGY ABSORPTION; ENERGY LOSSES; EXTREME ULTRAVIOLET RADIATION; FLARING; IRON IONS; LINE BROADENING; MASS; RESOLUTION; SOLAR CORONA; SOLAR FLARES; SUN; X RADIATION

Citation Formats

Li, Y., Ding, M. D., Qiu, J., and Cheng, J. X., E-mail: yingli@nju.edu.cn. CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITH IRIS AND EIS. United States: N. p., 2015. Web. doi:10.1088/0004-637X/811/1/7.
Li, Y., Ding, M. D., Qiu, J., & Cheng, J. X., E-mail: yingli@nju.edu.cn. CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITH IRIS AND EIS. United States. doi:10.1088/0004-637X/811/1/7.
Li, Y., Ding, M. D., Qiu, J., and Cheng, J. X., E-mail: yingli@nju.edu.cn. 2015. "CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITH IRIS AND EIS". United States. doi:10.1088/0004-637X/811/1/7.
@article{osti_22525431,
title = {CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITH IRIS AND EIS},
author = {Li, Y. and Ding, M. D. and Qiu, J. and Cheng, J. X., E-mail: yingli@nju.edu.cn},
abstractNote = {Chromospheric evaporation refers to dynamic mass motions in flare loops as a result of rapid energy deposition in the chromosphere. These motions have been observed as blueshifts in X-ray and extreme-ultraviolet (EUV) spectral lines corresponding to upward motions at a few tens to a few hundreds of km s{sup −1}. Past spectroscopic observations have also revealed a dominant stationary component, in addition to the blueshifted component, in emission lines formed at high temperatures (∼10 MK). This is contradictory to evaporation models predicting predominant blueshifts in hot lines. The recently launched Interface Region Imaging Spectrograph (IRIS) provides high-resolution imaging and spectroscopic observations that focus on the chromosphere and transition region in the UV passband. Using the new IRIS observations, combined with coordinated observations from the EUV Imaging Spectrometer, we study the chromospheric evaporation process from the upper chromosphere to the corona during an X1.0 flare on 2014 March 29. We find evident evaporation signatures, characterized by Doppler shifts and line broadening, at two flare ribbons that are separating from each other, suggesting that chromospheric evaporation takes place in successively formed flaring loops throughout the flare. More importantly, we detect dominant blueshifts in the high-temperature Fe xxi line (∼10 MK), in agreement with theoretical predictions. We also find that, in this flare, gentle evaporation occurs at some locations in the rise phase of the flare, while explosive evaporation is detected at some other locations near the peak of the flare. There is a conversion from gentle to explosive evaporation as the flare evolves.},
doi = {10.1088/0004-637X/811/1/7},
journal = {Astrophysical Journal},
number = 1,
volume = 811,
place = {United States},
year = 2015,
month = 9
}
  • With observations from the Interface Region Imaging Spectrograph, we track the complete evolution of ∼11 MK evaporation flows in an M1.1 flare on 2014 September 6 and an X1.6 flare on 2014 September 10. These hot flows, as indicated by the blueshifted Fe xxi 1354.08 Å line, evolve smoothly with a velocity decreasing exponentially from ∼200 km s{sup −1} to almost stationary within a few minutes. We find a good correlation between the flow velocity and energy deposition rate as represented by the hard X-ray flux observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager, or time derivative ofmore » the soft X-ray flux observed with the Geostationary Operational Environmental Satellites and the HINODE X-ray Telescope, which is in general agreement with models of nonthermal electron heating. The maximum blueshift of Fe xxi appears approximately at the same time as or slightly after the impulsive enhancement of the ultraviolet continuum and the Mg ii 2798.8 Å line emission, demonstrating that the evaporation flow is closely related to heating of the lower chromosphere. Finally, while the hot Fe xxi 1354.08 Å line is entirely blueshifted with no obvious rest component, cool chromospheric and transition region lines like Si iv 1402.77 Å are often not entirely redshifted but just reveal an obvious red wing enhancement at the ribbons, suggesting that the speed of chromospheric condensation might be larger than previously thought.« less
  • The dynamics of hot chromospheric plasma of solar flares is a key to understanding the mechanisms of flare energy release and particle acceleration. A moderate M1.0 class flare of 2014 June 12, (SOL2014-06-12T21:12) was simultaneously observed by NASA's Interface Region Imaging Spectrograph (IRIS) and other spacecraft, and also by the New Solar Telescope at the BBSO. This paper presents the first part of our investigation focused on analysis of the IRIS data. Our analysis of the IRIS data in different spectral lines reveals a strong redshifted jet-like flow with a speed of ∼100 km s{sup −1} of the chromospheric material beforemore » the flare. Strong nonthermal emission of the C ii k 1334.5 Å line, formed in the chromosphere–corona transition region, is observed at the beginning of the impulsive phase in several small (with a size of ∼1″) points. It is also found that the C ii k line is redshifted across the flaring region before, during, and after the impulsive phase. A peak of integrated emission of the hot (1.1 · 10{sup 7} K) plasma in the Fe xxi 1354.1 Å line is detected approximately five minutes after the integrated emission peak of the lower temperature C ii k. A strong blueshift of the Fe xxi line across the flaring region corresponds to evaporation flows of the hot chromospheric plasma with a speed of 50 km s{sup −1}. Additional analysis of the RHESSI data supports the idea that the upper chromospheric dynamics observed by IRIS has features of “gentle” evaporation driven by heating of the solar chromosphere by accelerated electrons and by a heat flux from the flare energy release site.« less
  • We have observed the flare of 1980 May 7 1456 UT with several Solar Meaximum Mission instruments, in coordination with the Sacramento Peak Observatory vacuum tower telescope. From the X-ray data we are able to determine the total emission measure of all material at T>2 x 10/sup 6/ K, commonly attributed to chromospheric evaporation. Volume estimates from X-ray and H..cap alpha.. images lead to an estimate of the number of electrons in the soft X-ray plasma. Comparison of theoretical calculations of the H..cap alpha.. signature of an evaporated state of the chromosphere to H..cap alpha.. line profile observations shows thatmore » chromospheric evaporation indeed has taken place concurrently with the appearance of the X-ray plasma. We have determined the amount of material that has been evaporated from the chromosphere, relative to the preflare state. This leads us to the conclusion that more than enough material has been evaporated from the chromosphere to account for the material in the X-ray plasma. Taken together, the H..cap alpha.., soft, and hard X-ray images suggest that chromospheric evaporation is driven by two mechanisms. During the impulsive phase, there is evidence that chromospheric evaporation is due to flare-accelerated electrons. During the thermal phase, it appears to be driven by thermal conduction from the hot coronal plasma created earlier in the flare.« less
  • From the Solar Maximum Mission (SMM) and Sacramento Peak Observatory (SPO) we observed the compact solar flare of 1980 May 7, previously studied by Acton et al. (1982) and Simnett (1983), with spatial, spectral, and temporal resolution in both X-rays and H..cap alpha.. profiles based on physical models of chromospheric flare processes and model parameters inferred from the X-ray observations.
  • The entire profile of the Fe XXIII line at 263.8 A, formed at temperature Almost-Equal-To 14 MK, was blueshifted by an upward velocity -122 {+-} 33 km s{sup -1} when it was first detected by the Extreme-ultraviolet Imaging Spectrometer operating in rapid cadence (11.18 s) stare mode during a C1 solar flare. The entire profile became even more blueshifted over the next two exposures, when the upward velocity reached its maximum of -208 {+-} 14 km s{sup -1} before decreasing to zero over the next 12 exposures. After that, a weak, secondary blueshifted component appeared for five exposures, reached amore » maximum upward velocity of -206 {+-} 33 km s{sup -1}, and disappeared after the maximum line intensity (stationary plus blueshifted) was achieved. Velocities were measured relative to the intense stationary profile observed near the flare's peak and early during its decline. The initial episode during which the entire profile was blueshifted lasted about 156 s, while the following episode during which a secondary blueshifted component was detected lasted about 56 s. The first episode likely corresponds to chromospheric evaporation in a single loop strand, while the second corresponds to evaporation in an additional strand, as described in multi-strand flare loop models proposed by Hori et al. and Warren and Doschek. Line emission from progressively cooler ions (Fe XVII, XVI, and XIV) brightened at successively later times, consistent with cooling of flare-heated plasma.« less