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Electron Acceleration in Solar Flares

Published online by Cambridge University Press:  12 April 2016

Wolfgang Dröge ,
Peter Meyer ,
Paul Evenson  and
Dan Moses
Wolfgang Dröge
Affiliation:
Enrico Fermi Institute, University of Chicago, 933 East 56th Street, Chicago, IL 60637, U.S.A.
Peter Meyer
Affiliation:
Enrico Fermi Institute, University of Chicago, 933 East 56th Street, Chicago, IL 60637, U.S.A.
Paul Evenson
Affiliation:
Bartol Research Institute, University of Delaware, Newark, DE 19716, U.S.A.
Dan Moses
Affiliation:
American Science and Engineering Inc., Fort Washington, Cambridge, MA 02139, U.S.A.

Abstract

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For the period September 1978 to December 1982 we have identified 55 solar flare particle events for which our instruments on board the ISEE-3 (ICE) spacecraft detected electrons above 10 MeV. Combining our data with those from the ULEWAT spectrometer (MPI Garching and University of Maryland) electron spectra in the range from 0.1 to 100 MeV were obtained. The observed spectral shapes can be divided into two classes. The spectra of the one class can be fit by a single power law in rigidity over the entire observed range. The spectra of the other class deviate from a power law, instead exhibiting a steepening at low rigidities and a flattening at high rigidities. Events with power-law spectra are associated with impulsive (< 1 hr duration) soft X-ray emission, whereas events with hardening spectra are associated with long-duration (> 1 hr) soft X-ray emission. The characteristics of long-duration events are consistent with diffusive shock acceleration taking place high in the corona. Electron spectra of short-duration flares are well reproduced by the distribution functions derived from a model assuming simultaneous second-order Fermi acceleration and Coulomb losses operating in closed flare loops.

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 104 , Issue 1: Solar and Stellar Flares , 1989 , pp. 95 - 103
Copyright
Copyright © Kluwer 1989

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