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Energetic-particle abundances in impulsive solar flare eventsWe report on the abundances of energetic particles from impulsive solar flares, including those from a survey of 228 He-3 rich events, with He-3/He-4 is greater than 0.1, observed by the International Sun Earth Explorer (ISEE) 3 spacecraft from 1978 August through 1991 April. The rate of occurrence of these events corresponds to approximately 1000 events/yr on the solar disk at solar maximum. Thus the resonant plasma processes that enhance He-3 and heavy elements are a common occurrence in impulsive solar flares. To supply the observed fluence of He-3 in large events, the acceleration must be highly efficient and the source region must be relatively deep in the atmosphere at a density of more than 10(exp 10) atoms/cu cm. He-3/He-4 may decrease in very large impulsive events because of depletion of He-3 in the source region. The event-to-event variations in He-3/He-4, H/He-4, e/p, and Fe/C are uncorrelated in our event sample. Abundances of the elements show a pattern in which, relative to coronal composition, He-4, C, N, and O have normal abundance ratios, while Ne, Mg, and Si are enhanced by a factor approximately 2.5 and Fe by a factor approximately 7. This pattern suggests that elements are accelerated from a region of the corona with an electron temperature of approximately 3-5 MK, where elements in the first group are fully ionized (Q/A = 0.5), those in the second group have two orbital electrons (Q/A approximately 0.43), and Fe has Q/A approximately 0.28. Ions with the same gyrofrequency absorb waves of that frequency and are similarly accelerated and enhanced. Further stripping may occur after acceleration as the ions begin to interact with the streaming electrons that generated the plasma waves.
Document ID
19950035972
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Reames, D. V.
(NASA Goddard Space Flight Center Greenbelt, MD, US, United States)
Meyer, J. P.
(NASA Goddard Space Flight Center Greenbelt, MD, US, United States)
Von Rosenvinge, T. T.
(NASA Goddard Space Flight Center Greenbelt, MD, US, United States)
Date Acquired
August 16, 2013
Publication Date
February 1, 1994
Publication Information
Publication: Astrophysical Journal Supplement Series
Volume: 90
Issue: 2
ISSN: 0067-0049
Subject Category
Solar Physics
Accession Number
95A67571
Distribution Limits
Public
Copyright
Other

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