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Collisionless shock formation and the prompt acceleration of solar flare ionsThe formation mechanisms of collisionless shocks in solar flare plasmas are investigated. The priamry flare energy release is assumed to arise in the coronal portion of a flare loop as many small regions or 'hot spots' where the plasma beta locally exceeds unity. One dimensional hybrid numerical simulations show that the expansion of these 'hot spots' in a direction either perpendicular or oblique to the ambient magnetic field gives rise to collisionless shocks in a few Omega(i), where Omega(i) is the local ion cyclotron frequency. For solar parameters, this is less than 1 second. The local shocks are then subsequently able to accelerate particles to 10 MeV in less than 1 second by a combined drift-diffusive process. The formation mechanism may also give rise to energetic ions of 100 keV in the shock vicinity. The presence of these energetic ions is due either to ion heating or ion beam instabilities and they may act as a seed population for further acceleration. The prompt acceleration of ions inferred from the Gamma Ray Spectrometer on the Solar Maximum Mission can thus be explained by this mechanism.
Document ID
Document Type
Reprint (Version printed in journal)
Cargill, P. J.
(Maryland Univ. College Park, MD, United States)
Goodrich, C. C.
(Maryland, University College Park, United States)
Vlahos, L.
(Salonika, University Greece)
Date Acquired
August 13, 2013
Publication Date
January 1, 1988
Publication Information
Publication: Astronomy and Astrophysics
Volume: 189
Issue: 1-2
ISSN: 0004-6361
Subject Category
Solar Physics
Funding Number(s)
Distribution Limits
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