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Balloon observations of Galactic cosmic ray helium before and during a Forbush decreaseThe energy spectrum of Galactic cosmic ray helium was measured in two different balloon experiments launched four days apart from Canada: SMILI-I on Sept 1, 1989 and MASS on Sept 5, 1989. A slow Forbush decrease began on Sept 4, 1989 and had not reached its maximum at the time of the MASS flight. Comparison of the balloon measurements shows a fractional decrease of 0.37 to 0.15 in the Helium flux between 200 and 450 MeV/nucleon (1.2-2.0 GV). The rigidity dependence is analyzed in two models and found to be steeper than previous observations. Interplanetary particle data and ground-based Neutron Monitor results are consistent with the balloon observations. Probable sources for this Forbush decrease are discussed.
Document ID
19940035196
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Clem, J. M.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Guzik, T. G.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Lijowski, M.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Wefel, J. P.
(Louisiana State Univ. Baton Rouge, United States)
Beatty, J. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Ficenec, D. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Tobias, S.
(Washington Univ. Saint Louis, MO, United States)
Mitchell, J. W.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Mckee, S.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Nutter, S.
(Michigan Univ. Ann Arbor, United States)
Date Acquired
August 16, 2013
Publication Date
September 3, 1993
Publication Information
Publication: Geophysical Research Letters
Volume: 20
Issue: 17
ISSN: 0094-8276
Subject Category
Space Radiation
Accession Number
94A11851
Funding Number(s)
CONTRACT_GRANT: NAGW-1032
CONTRACT_GRANT: NAGW-1642
CONTRACT_GRANT: NAGW-1035
CONTRACT_GRANT: NAGW-2990
CONTRACT_GRANT: NAGW-1027
CONTRACT_GRANT: NAGW-2138
Distribution Limits
Public
Copyright
Other

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