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Electron acceleration in solar flaresFor the period Spetember 1978 to December 1982, 55 solar flare particle events for which the instruments on board the ISEE-3 spacecraft detected electrons above 10 MeV. Combining data with those from the ULEWAT spectrometer 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 (less than 1 hr duration) soft X-ray emission, whereas events with hardening spectra are associated with long-duration (more than 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.
Document ID
19900027752
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Droge, Wolfgang
(Chicago Univ. Chicago, IL, United States)
Meyer, Peter
(Chicago, University IL, United States)
Evenson, Paul
(Delaware, University Newark, United States)
Moses, Dan
(American Science and Engineering, Inc. Cambridge, MA, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1989
Publication Information
Publication: Solar Physics
Volume: 121
Issue: 2-Jan
ISSN: 0038-0938
Subject Category
Solar Physics
Accession Number
90A14807
Funding Number(s)
CONTRACT_GRANT: NAS5-25496
CONTRACT_GRANT: NAS5-28500
Distribution Limits
Public
Copyright
Other

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