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Ulysses at 50° south: constant immersion in the high‐speed solar wind
Author(s) -
Phillips J. L.,
Balogh A.,
Bame S. J.,
Goldstein B. E.,
Gosling J. T.,
Hoeksema J. T.,
McComas D. J.,
Neugebauer M.,
Sheeley N. R.,
Wang Y.M.
Publication year - 1994
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 - 10.1029/94gl01065
Subject(s) - coronal hole , solar wind , physics , coronal mass ejection , polar , latitude , wind speed , atmospheric sciences , astrophysics , astronomy , corona (planetary geology) , plasma , meteorology , astrobiology , quantum mechanics , venus
We present speed observations from the Ulysses solar wind plasma experiment through 50° south latitude. The pronounced speed modulation arising from solar rotation and the tilt of the heliomagnetic current sheet has nearly disappeared. Ulysses is now observing wind speeds in the 700 to 800 km s −1 range, with a magnetic polarity indicating an origin in the large south polar coronal hole. The strong compressions, rarefactions, and shock waves previously seen have weakened or disappeared. Occasional coronal mass ejections characterized by low plasma density caused by radial expansion have been observed. The coronal configuration was simple and stable in 1993, indicating that the observed solar wind changes were caused by increasing spacecraft latitude. Trends in prevailing speed with increasing latitude support previous findings. A decrease in peak speed southward of 40° latitude may indicate that the fastest solar wind comes from the equatorial extensions of the polar coronal holes.