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A hybrid thermal/nonthermal model for the energetic emissions from solar flaresWe present an alternative interpretation of the high-resolution solar flare spectra obtained in 1981 by Lin et al. In our interpretation electron heating and acceleration are simultaneous and physically linked, rather than heating being a secondary effect of particle acceleration. We show that the observed properties of solar flare X-ray emission can in general be explained through the Joule heating and electric field acceleration of runaway electrons in current channels. We have fitted a hybrid thermal/nonthermal electron distribution, consisting of hot isothermal electrons with a nonthermal tail of runaway electrons, to representative spectra obtained by Lin et al. The hybrid model relaxes the electron number and energy flux requirements for the hard X-ray emission over those of a purely nonthermal model. The low-energy 'cutoff' to the nonthermal part of the X-ray spectrum is determined by the critical velocity in the electron distribution above which runaway acceleration occurs. We relate the fit parameters to the physical properties (such as the electric field strength in the current channels) of the acceleration region.
Document ID
19930032466
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Holman, Gordon D.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Benka, Stephen G.
(U.S. Navy, Naval Research Lab. Washington, United States)
Date Acquired
August 15, 2013
Publication Date
December 1, 1992
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 400
Issue: 2
ISSN: 0004-637X
Subject Category
Solar Physics
Accession Number
93A16463
Funding Number(s)
PROJECT: RTOP 170-38-53-16
Distribution Limits
Public
Copyright
Other

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