Onset of electron acceleration in a flare loop

Sharykin, I., Liu, S. and Fletcher, L. (2014) Onset of electron acceleration in a flare loop. Astrophysical Journal, 793(1), pp. 25-34. (doi: 10.1088/0004-637X/793/1/25)

98994.pdf - Accepted Version



We carried out detailed analysis of X-ray and radio observations of a simple flare loop that occurred on 12th August 2002, 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 keVs. A power-law high-energy spec- tral 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 dis- appearance of this nonthermal component. These results suggest that electron acceleration only covers a central period of a longer and more gradual energy dis- sipation 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 a quasi- steady state of the electron accelerator, 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.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Fletcher, Professor Lyndsay and Liu, Dr Siming
Authors: Sharykin, I., Liu, S., and Fletcher, L.
Subjects:Q Science > QB Astronomy
Q Science > QC Physics
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Group:Astronomy and Astrophysics
Journal Name:Astrophysical Journal
Publisher:Institute of Physics
ISSN (Online):1538-4357
Copyright Holders:Copyright © 2014 The American Astronomical Society
First Published:First published in the Astrophysical Journal 793(1):25-34
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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