THE HIGH-LATITUDE SOLAR-WIND NEAR SUNSPOT MAXIMUM

Citation
Ym. Wang et Nr. Sheeley, THE HIGH-LATITUDE SOLAR-WIND NEAR SUNSPOT MAXIMUM, Geophysical research letters, 24(24), 1997, pp. 3141-3144
Citations number
13
ISSN journal
00948276
Volume
24
Issue
24
Year of publication
1997
Pages
3141 - 3144
Database
ISI
SICI code
0094-8276(1997)24:24<3141:THSNSM>2.0.ZU;2-K
Abstract
We use an empirical relation between solar wind speed and coronal flux -tube expansion to predict what Ulysses might have seen had it flown o ver the solar poles during 1989-1991 instead of 1994-1996. The wind sp eed patterns, derived from solar magnetograph data, show the following characteristics: (1) high-speed streams having recurrence rates of 28 -29 days and originating from midlatitude extensions of the polar coro nal holes dominate the rising phase of the sunspot cycle (1987-1989); (2) the persistent high-speed polar wind disappears and low-speed wind is found at all latitudes during 1989-1990; (3) very fast, episodic ' 'polar jets'' are generated as active region fields surge to the poles at the time of polar field reversal (1990-1991). The wind speed patte rns that Ulysses encounters during its second polar orbit are expected to show the same general characteristics.