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| Titel |
Statistical analysis of long-duration low-density solar wind events |
| VerfasserIn |
S. Watari, T. Watanabe, K. Marubashi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 19, no. 1 ; Nr. 19, no. 1, S.17-23 |
| Datensatznummer |
250014173
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| Publikation (Nr.) |
 copernicus.org/angeo-19-17-2001.pdf |
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| Zusammenfassung |
Low solar wind density
with long duration was measured by in situ observation between 11 and 12 May
1999. As a result of this low-density solar wind condition, the magnetosphere of
the Earth expanded considerably. We used a database of one-hour-averaged solar
wind (1963–1999) near 1 AU to determine whether or not the observed
low-density event was extremely abnormal. As a result it was found that this
event has the longest duration in approximately 36 years of solar wind
observations. There are three events with density 0.5 cm-3 or less and
duration ten hours or longer. They were observed on 4 and 31 July 1979, and 11–12
May 1999. The 4 July 1979 event recurred on 31 July 1979. The events were
characterized by low-beta, low Alfven Mach number (MA ), and low dynamic
pressure. The occurrence rate of low-density solar wind with density 0.5 cm-3
or less shows several peaks near solar maxima. However, it is difficult to find
a clear relationship between the sunspot number and the occurrence rate.
Key words. Interplanetary physics (flare and stream
dynamics; solar wind plasma; sources of the solar wind) |
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