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Solar wind and coronal structure near sunspot minimum - Pioneer and SMM observations from 1985-1987Changes in solar wind speed and magnetic polarity observed at the Pioneer spacecraft are discussed here in terms of the changing magnetic geometry implied by SMM coronagraph observations over the period 1985-1987. The pattern of recurrent solar wind streams, the long-term average speed, and the sector polarity of the interplanetary magnetic field all changed in a manner suggesting both a temporal variation, and a changing dependence on heliographic latitude. Coronal observations during this epoch show a systematic variation in coronal structure and the magnetic structure imposed on the expanding solar wind. These observations suggest interpretation of the solar wind speed variations in terms of the familiar model where the speed increases with distance from a nearly flat interplanetary current sheet, and where this current sheet becomes aligned with the solar equatorial plane as sunspot minimum approaches, but deviates rapidly from that orientation after minimum.
Document ID
Document Type
Reprint (Version printed in journal)
Mihalov, J. D. (NASA Ames Research Center Moffett Field, CA, United States)
Barnes, A. (NASA Ames Research Center Moffett Field, CA, United States)
Hundhausen, A. J. (High Altitude Observatory Boulder, CO, United States)
Smith, E. J. (JPL Pasadena, CA, United States)
Date Acquired
August 14, 2013
Publication Date
June 1, 1990
Publication Information
Publication: Journal of Geophysical Research
Volume: 95
ISSN: 0148-0227
Subject Category
Distribution Limits