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Title: ON THE RELATIONSHIP BETWEEN A HOT-CHANNEL-LIKE SOLAR MAGNETIC FLUX ROPE AND ITS EMBEDDED PROMINENCE

Abstract

A magnetic flux rope (MFR) is a coherent and helical magnetic field structure that has recently been found likely to appear as an elongated hot channel prior to a solar eruption. In this Letter, we investigate the relationship between the hot channel and the associated prominence through analysis of a limb event on 2011 September 12. In the early rise phase, the hot channel was initially cospatial with the prominence. It then quickly expanded, resulting in a separation of the top of the hot channel from that of the prominence. Meanwhile, they both experienced an instantaneous morphology transformation from a Λ shape to a reversed-Y shape and the top of these two structures showed an exponential increase in height. These features are a good indication of the occurrence of kink instability. Moreover, the onset of kink instability is found to coincide in time with the impulsive enhancement of flare emission underneath the hot channel, suggesting that ideal kink instability likely also plays an important role in triggering fast flare reconnection besides initiating the impulsive acceleration of the hot channel and distorting its morphology. We conclude that the hot channel is most likely the MFR system and the prominence only correspondsmore » to the cool materials that are collected in the bottom of the helical field lines of the MFR against gravity.« less

Authors:
; ; ; ; ;  [1];  [2]
  1. School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)
  2. Department of Physics, Indian Institute of Technology (IIT)-BHU, Varanasi-221005 (India)
Publication Date:
OSTI Identifier:
22365658
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 789; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; FILAMENTS; GRAVITATION; HOT CHANNEL; KINK INSTABILITY; MAGNETIC FIELDS; MAGNETIC FLUX; MASS; MORPHOLOGY; SOLAR CORONA; SOLAR PROMINENCES; SUN; TRANSFORMATIONS

Citation Formats

Cheng, X., Ding, M. D., Zhang, J., Guo, Y., Chen, P. F., Sun, J. Q., and Srivastava, A. K., E-mail: xincheng@nju.edu.cn. ON THE RELATIONSHIP BETWEEN A HOT-CHANNEL-LIKE SOLAR MAGNETIC FLUX ROPE AND ITS EMBEDDED PROMINENCE. United States: N. p., 2014. Web. doi:10.1088/2041-8205/789/2/L35.
Cheng, X., Ding, M. D., Zhang, J., Guo, Y., Chen, P. F., Sun, J. Q., & Srivastava, A. K., E-mail: xincheng@nju.edu.cn. ON THE RELATIONSHIP BETWEEN A HOT-CHANNEL-LIKE SOLAR MAGNETIC FLUX ROPE AND ITS EMBEDDED PROMINENCE. United States. doi:10.1088/2041-8205/789/2/L35.
Cheng, X., Ding, M. D., Zhang, J., Guo, Y., Chen, P. F., Sun, J. Q., and Srivastava, A. K., E-mail: xincheng@nju.edu.cn. Thu . "ON THE RELATIONSHIP BETWEEN A HOT-CHANNEL-LIKE SOLAR MAGNETIC FLUX ROPE AND ITS EMBEDDED PROMINENCE". United States. doi:10.1088/2041-8205/789/2/L35.
@article{osti_22365658,
title = {ON THE RELATIONSHIP BETWEEN A HOT-CHANNEL-LIKE SOLAR MAGNETIC FLUX ROPE AND ITS EMBEDDED PROMINENCE},
author = {Cheng, X. and Ding, M. D. and Zhang, J. and Guo, Y. and Chen, P. F. and Sun, J. Q. and Srivastava, A. K., E-mail: xincheng@nju.edu.cn},
abstractNote = {A magnetic flux rope (MFR) is a coherent and helical magnetic field structure that has recently been found likely to appear as an elongated hot channel prior to a solar eruption. In this Letter, we investigate the relationship between the hot channel and the associated prominence through analysis of a limb event on 2011 September 12. In the early rise phase, the hot channel was initially cospatial with the prominence. It then quickly expanded, resulting in a separation of the top of the hot channel from that of the prominence. Meanwhile, they both experienced an instantaneous morphology transformation from a Λ shape to a reversed-Y shape and the top of these two structures showed an exponential increase in height. These features are a good indication of the occurrence of kink instability. Moreover, the onset of kink instability is found to coincide in time with the impulsive enhancement of flare emission underneath the hot channel, suggesting that ideal kink instability likely also plays an important role in triggering fast flare reconnection besides initiating the impulsive acceleration of the hot channel and distorting its morphology. We conclude that the hot channel is most likely the MFR system and the prominence only corresponds to the cool materials that are collected in the bottom of the helical field lines of the MFR against gravity.},
doi = {10.1088/2041-8205/789/2/L35},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 789,
place = {United States},
year = {Thu Jul 10 00:00:00 EDT 2014},
month = {Thu Jul 10 00:00:00 EDT 2014}
}
  • Hot channels (HCs), high-temperature erupting structures in the lower corona of the Sun, have been proposed as a proxy of magnetic flux ropes (MFRs) since their initial discovery. However, it is difficult to provide definitive proof given the fact that there is no direct measurement of the magnetic field in the corona. An alternative method is to use the magnetic field measurement in the solar wind from in situ instruments. On 2012 July 12, an HC was observed prior to and during a coronal mass ejection (CME) by the Atmospheric Imaging Assembly high-temperature images. The HC is invisible in themore » EUVI low-temperature images, which only show the cooler leading front (LF). However, both the LF and an ejecta can be observed in the coronagraphic images. These are consistent with the high temperature and high density of the HC and support that the ejecta is the erupted HC. Meanwhile, the associated CME shock was identified ahead of the ejecta and the sheath through the COR2 images, and the corresponding ICME was detected by the Advanced Composition Explorer, showing the shock, sheath, and magnetic cloud (MC) sequentially, which agrees with the coronagraphic observations. Further, the MC average Fe charge state is elevated, containing a relatively low-ionization-state center and a high-ionization-state shell, consistent with the preexisting HC observation and its growth through magnetic reconnection. All of these observations support that the MC detected near the Earth is the counterpart of the erupted HC in the corona for this event. The study provides strong observational evidence of the HC as an MFR.« less
  • We describe and use novel techniques to analyze a striking and distinct solar wind event observed by two spacecraft. We show that the event is consistent with an interpretation as a torsional Alfven wave embedded within a small, nearly radially aligned, magnetic flux rope of total width {approx}10{sup 6} km. It seems likely that the torsional wave was generated by distortions produced within a pre-existing flux rope that erupted from the Sun. Our examination of many events previously identified as flux ropes in the solar wind indicates that torsional Alfven waves are extremely rare in such events.
  • The magnetic configuration hosting prominences and their surrounding coronal structure is a key research topic in solar physics. Recent theoretical and observational studies strongly suggest that a helical magnetic flux rope is an essential ingredient to fulfill most of the theoretical and observational requirements for hosting prominences. To understand flux rope formation details and obtain magnetic configurations suitable for future prominence formation studies, we here report on three-dimensional isothermal magnetohydrodynamic simulations including finite gas pressure and gravity. Starting from a magnetohydrostatic corona with a linear force-free bipolar magnetic field, we follow its evolution when introducing vortex flows around the mainmore » polarities and converging flows toward the polarity inversion line near the bottom of the corona. The converging flows bring the feet of different loops together at the polarity inversion line, where magnetic reconnection and flux cancellation happen. Inflow and outflow signatures of the magnetic reconnection process are identified, and thereby the newly formed helical loops wind around preexisting ones so that a complete flux rope grows and ascends. When a macroscopic flux rope is formed, we switch off the driving flows and find that the system relaxes to a stable state containing a helical magnetic flux rope embedded in an overlying arcade structure. A major part of the formed flux rope is threaded by dipped field lines that can stably support prominence matter, while the total mass of the flux rope is in the order of 4-5× 10{sup 14} g.« less
  • We present the analysis of an unusual failed eruption captured in high cadence and in many wavelengths during the observing campaign in support of the Very high Angular resolution Ultraviolet Telescope ( VAULT2.0 ) sounding rocket launch. The refurbished VAULT2.0 is a Ly α ( λ 1216 Å) spectroheliograph launched on 2014 September 30. The campaign targeted active region NOAA AR 12172 and was closely coordinated with the Hinode and IRIS missions and several ground-based observatories (NSO/IBIS, SOLIS, and BBSO). A filament eruption accompanied by a low-level flaring event (at the GOES C-class level) occurred around the VAULT2.0 launch. Nomore » coronal mass ejection was observed. The eruption and its source region, however, were recorded by the campaign instruments in many atmospheric heights ranging from the photosphere to the corona in high cadence and spatial resolution. This is a rare occasion that enabled us to perform a comprehensive investigation on a failed eruption. We find that a rising Magnetic Flux Rope (MFR)-like structure was destroyed during its interaction with the ambient magnetic field, creating downflows of cool plasma and diffuse hot coronal structures reminiscent of “cusps.” We employ magnetofrictional simulations to show that the magnetic topology of the ambient field is responsible for the destruction of the MFR. Our unique observations suggest that the magnetic topology of the corona is a key ingredient for a successful eruption.« less
  • Corona structures and processes during the pre-impulsive stage of solar eruption are crucial to understanding the physics leading to the subsequent explosive energy release. Here we present the first microwave imaging study of a hot flux rope structure during the pre-impulsive stage of an eruptive M7.7 solar flare, with the Nobeyama Radioheliograph at 17 GHz. The flux rope is also observed by the SDO/AIA in its hot passbands of 94 and 131 Å. In the microwave data, it is revealed as an overall arcade-like structure consisting of several intensity enhancements bridged by generally weak emissions, with brightness temperatures (T{sub B})more » varying from ∼10,000 K to ∼20,000 K. Locations of microwave intensity enhancements along the structure remain relatively fixed at certain specific parts of the flux rope, indicating that the distribution of emitting electrons is affected by the large-scale magnetic configuration of the twisted flux rope. Wavelet analysis shows a pronounced 2 minute period of the microwave T{sub B} variation during the pre-impulsive stage of interest. The period agrees well with that reported for AIA sunward-contracting loops and upward ejective plasmoids (suggested to be reconnection outflows). This suggests that both periodicities are controlled by the same reconnection process that takes place intermittently at a 2 minute timescale. We infer that at least a part of the emission is excited by non-thermal energetic electrons via the gyro-synchrotron mechanism. The study demonstrates the potential of microwave imaging in exploring the flux rope magnetic geometry and relevant reconnection process during the onset of solar eruption.« less