The Forbush Predecrease
Journal Article
·
· Journal of Geophysical Research
Forbush decreases observed by superneutron monitors are frequently preceded by an almost equally large predecrease. Five such events are studied here, and there are two main observational results: (1) the predecrease represents a cosmicray depletion in a narrow range of pitch angles ( plus or minus 30 deg ) around the mean interplanetary field direction and (2) the predecrease has an unusual rigidity dependence inasmuch as its amplitude inreases with rigidity, going something like R/sup 0.5 yields 1.5/up to a limit of about 80 Gv. Both these results can be accounted for by a model of the interplanetary magnetic field that generates the Forbush decrease and the predecrease by way of a propagating disturbance from the Sun. Using Barnden's (1971) work, it appears that such a model requires cosmic-ray mean free path at increases with rigidity according to R/sup 1 yields 2/.
- Research Organization:
- Univ. of Denver
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-29-013348
- OSTI ID:
- 4368358
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: 4 Vol. 78; ISSN 0148-0227
- Publisher:
- American Geophysical Union
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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