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Microstructure of the interplanetary magnetic field near 4 and 5 AUInterplanetary magnetic field fluctuations near 4 and 5 AU are investigated on the basis of Pioneer 10 and 11 vector magnetic field measurements in order to identify extant wave modes and propagation directions as functions of frequency in the range 0.00004 to 0.009 Hz. Analysis of the approximately 500 spectral matrices as functions of frequency obtained from each spacecraft indicates the distributions of maximum variance directions to be peaked along the normal to the plane of the minimum variance direction and the mean magnetic field, as would be expected for a planar, small-amplitude Alfven wave with a minimum variance direction close to the wave vector. It is thus inferred that single small-amplitude Alfven waves are occasionally present in the temporal and frequency bands analyzed, however waves with wave vectors not well approximated by the minimum variance direction, Alfven wave ensembles, finite-amplitude waves and nonplanar fluctuations may also be present. Observations are also noted to suggest the predominance of the Alfven mode over the fast and slow modes, however do not support theoretical models of outward propagating plane Alfven waves of solar origin.
Document ID
19800065027
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Parker, G. D.
(Norwich University Northfield, Vt., United States)
Date Acquired
August 10, 2013
Publication Date
August 1, 1980
Publication Information
Publication: Journal of Geophysical Research
Volume: 85
Subject Category
Astrophysics
Accession Number
80A49197
Funding Number(s)
CONTRACT_GRANT: NSG-07024
CONTRACT_GRANT: NSF ATM-79-11109
Distribution Limits
Public
Copyright
Other

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