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Propagation of a Forbush decrease in cosmic ray intensity to 15.9 AUBy observation of the large Forbush decrease in cosmic-ray intensity of April-May 1978 at heliocentric radial distances of 1.01, 6.97, and 15.91 AU, it is found that the causative magnetized plasma cloud moved outward from the sun at an apparent radial speed of about 960 km/s, independent of radial distance over this range. Recovery from the impulsive decrease in intensity was markedly slower at the larger distances. On the basis of this fact and other considerations, several tentative suggestions are made as to the large-scale nature of Forbush decreases and their relationship to the 11-year solar modulation of galactic cosmic-ray intensity.
Document ID
19790061869
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Van Allen, J. A.
(Iowa, University Iowa City, Iowa, United States)
Date Acquired
August 9, 2013
Publication Date
July 1, 1979
Publication Information
Publication: Geophysical Research Letters
Volume: 6
Subject Category
Space Radiation
Report/Patent Number
AD-A075850
Accession Number
79A45882
Funding Number(s)
CONTRACT_GRANT: NAS2-6553
Distribution Limits
Public
Copyright
Other

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