Determination of the total accelerated electron rate and power using solar flare hard X-ray spectra

Kontar, E. P. , Jeffrey, N. L.S. and Emslie, A. G. (2019) Determination of the total accelerated electron rate and power using solar flare hard X-ray spectra. Astrophysical Journal, 871(2), 225. (doi:10.3847/1538-4357/aafad3)

193502.pdf - Accepted Version



Solar flare hard X-ray (HXR) spectroscopy serves as a key diagnostic of the accelerated electron spectrum. However, the standard approach using the collisional cold thick-target model poorly constrains the lower-energy part of the accelerated electron spectrum, hence the overall energetics of the accelerated electrons are typically constrained only to within one or two orders of magnitude. Here, we develop and apply a physically self-consistent, warm-target approach that involves the use of both HXR spectroscopy and imaging data. This approach allows an accurate determination of the electron distribution low-energy cutoff, and hence the electron acceleration rate and the contribution of accelerated electrons to the total energy released, by constraining the coronal plasma parameters. Using a solar flare observed in X-rays by RHESSI, we demonstrate that using the standard cold-target methodology, the low-energy cutoff (hence the energy content in electrons) is essentially undetermined. However, the warm-target methodology can determine the low-energy electron cutoff with ~7% uncertainty at the 3σ level, hence it permits an accurate quantitative study of the importance of accelerated electrons in solar flare energetics.

Item Type:Articles
Additional Information:A.G.E. was supported by grant NNX17AI16G from NASA's Heliophysics Supporting Research program.
Glasgow Author(s) Enlighten ID:Kontar, Professor Eduard and Jeffrey, Dr Natasha
Authors: Kontar, E. P., Jeffrey, N. L.S., and Emslie, A. G.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
Publisher:IOP Publishing
ISSN (Online):1538-4357
Published Online:04 February 2019
Copyright Holders:Copyright © 2019 The American Astronomical Society
First Published:First published in Astrophysical Journal 871(2):225
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
728901Consolidated Grant in Solar PhysicsLyndsay FletcherScience & Technology Facilities Council (STFC)ST/P000533/1S&E P&A - PHYSICS & ASTRONOMY