Collisional relaxation of electrons in a warm plasma and accelerated nonthermal electron spectra in solar flares

Kontar, E. P. , Jeffrey, N. L. S. , Emslie, A. G. and Bian, N. H. (2015) Collisional relaxation of electrons in a warm plasma and accelerated nonthermal electron spectra in solar flares. Astrophysical Journal, 809(1), 35. (doi: 10.1088/0004-637X/809/1/35)

Abstract

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 the effect of electron thermalization can be significant enough to nullify the need to introduce an ad hoc low-energy cutoff to the injected electron spectrum in order to keep the injected power in non-thermal electrons at a reasonable value. Rather, the suppression of the inferred low-energy end of the injected spectrum compared to that deduced from a cold-target analysis allows the inference from hard X-ray observations of a more realistic energy in injected non-thermal electrons in solar flares.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Jeffrey, Dr Natasha and Bian, Dr Nicolas Horace and Kontar, Professor Eduard
• Authors: Kontar, E. P., Jeffrey, N. L. S., Emslie, A. G., and Bian, N. H.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Astrophysical Journal
• Publisher: IOP Publishing
• ISSN: 0004-637X
• ISSN (Online): 1538-4357
• Copyright Holders: Copyright © 2015 IOP Publishing
• First Published: First published in Astrophysical Journal 809(1):35
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher.

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