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The band of solar wind variability at low heliographic latitudes near solar activity minimum: Plasma results from the Ulysses rapid latitude scan
Author(s) -
Gosling J. T.,
Bame S. J.,
Feldman W. C.,
McComas D. J.,
Phillips J. L.,
Goldstein B.,
Neugebauer M.,
Burkepile J.,
Hundhausen A. J.,
Acton L.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/95gl02163
Subject(s) - coronal hole , coronal mass ejection , physics , corona (planetary geology) , solar wind , heliosphere , solar minimum , coronal loop , helmet streamer , solar cycle 22 , astronomy , latitude , atmospheric sciences , astrophysics , solar cycle , plasma , astrobiology , quantum mechanics , venus
Near solar activity minimum large variations in the quiescent solar wind flow are confined to a narrow latitude band centered near the heliographic equator. During Ulysses' recent rapid latitude scan this band was ∼43° wide. Flow parameters poleward of the band in the opposite solar hemispheres were nearly the same. Main entry into the band of variable solar wind was via a shock disturbance most likely associated with over‐expansion of a coronal mass ejection event. Wind variability within the band was associated primarily with longitudinal structure in the solar corona and solar rotation; high‐speed streams observed there were associated with locations where the polar coronal holes extended equatorward toward the Ulysses orbit. Observations indicate that the polar coronal holes at this time occupied only ∼13% of the low corona, yet a nearly uniform high‐speed wind (average speed ∼750 km s −1 ) filled ∼63% of the heliosphere. This indicates the holes expanded by a factor of ∼4.8 from the low corona to interplanetary space. Much of this lateral expansion occurred beyond 1.74 solar radii from Sun center.