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Dependence of 50-keV upstream ion events at IMP 7 and 8 upon magnetic field bow shock geometryResults are presented for a statistical study of four years (1972-1976) of IMP 7 and 8 observations at approximately 40 R(E) of 50-200 keV upstream ion events measured with the Energetic Particle Experiment. A monotonic increase in the probability of observing upstream particle events is found with a decrease in the angle (theta-Bn) between the interplanetary magnetic field (IMF) and the local shock normal at the point where the IMF intersects the bow shock, independent of the length of time of bow shock connections exceeding approximately 10 min. Approximately equal probabilities are found for observing an event above a given flux from any portion of the bow shock with the same value of theta-Bn, a growth time of the 50-200 keV events of approximately 10 min, a maximum attainable flux of approximately 25,000/sq cm s sr, and a positive correlation between the probability of exceeding a given flux and the 3 hr Kp index. It is concluded that the local structure of the bow shock in the immediate vicinity of the field line connection is the dominant influence in the generation process of energetic upstream particle events and that wave-particle interactions produce a self-throttling mechanism that limits the maximum flux of ions escaping the upstream foreshock.
Document ID
19830056370
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Mitchell, D. G.
(Johns Hopkins Univ. Silver Spring, MD, United States)
Roelof, E. C.
(Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States)
Date Acquired
August 11, 2013
Publication Date
July 1, 1983
Publication Information
Publication: Journal of Geophysical Research
Volume: 88
ISSN: 0148-0227
Subject Category
Astrophysics
Accession Number
83A37588
Funding Number(s)
CONTRACT_GRANT: NSG-7055
CONTRACT_GRANT: N00024-83-C-5301
Distribution Limits
Public
Copyright
Other

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