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Solar-flare-induced Forbush decreases - Dependence on shock wave geometryIt is argued that the principal mechanism for the association of Forbush decreases with the passage of a solar flare shock wave is prolonged containment of cosmic ray particles behind the flare compression region, which acts as a semipermeable obstacle to particle motion along the field lines, leading to additional adiabatic cooling of the particles. Liouville's theorem is used to calculate the instantaneous distribution function at 1 AU for each particle arriving at the earth. By averaging over a large number of individual estimates, a representative estimate of the omnidirectional phase space density and the corresponding particle intensity is obtained. The energy change of individual particles at the shocks is found to be small in comparison to the energy lost by adiabatic cooling of the cosmic rays between the shock wave and the sun. The effects of particle rigidity, diffusion coefficient, and flare longitude on the magnitude of the Forbush decrease are quantitatively investigated.
Document ID
19840051846
Document Type
Reprint (Version printed in journal)
Authors
Thomas, B. T. (California Institute of Technology, Jet Propulsion Laboratory, Pasadena CA, United States)
Gall, R. (Universidad Nacional Autonoma de Mexico Mexico City, Mexico)
Date Acquired
August 12, 2013
Publication Date
May 1, 1984
Publication Information
Publication: Journal of Geophysical Research
Volume: 89
ISSN: 0148-0227
Subject Category
SPACE RADIATION
Funding Number(s)
CONTRACT_GRANT: NAS7-100
Distribution Limits
Public
Copyright
Other