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| Titel |
The solar and interplanetary causes of the recent minimum in geomagnetic activity (MGA23): a combination of midlatitude small coronal holes, low IMF BZ variances, low solar wind speeds and low solar magnetic fields |
| VerfasserIn |
B. T. Tsurutani, E. Echer, W. D. Gonzalez |
| 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 ; 29, no. 5 ; Nr. 29, no. 5 (2011-05-16), S.839-849 |
| Datensatznummer |
250017018
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| Publikation (Nr.) |
 copernicus.org/angeo-29-839-2011.pdf |
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| Zusammenfassung |
| Minima in geomagnetic activity (MGA) at Earth at the ends of SC23 and SC22
have been identified. The two MGAs (called MGA23 and MGA22, respectively)
were present in 2009 and 1997, delayed from the sunspot number minima in
2008 and 1996 by ~1/2–1 years. Part of the solar and interplanetary
causes of the MGAs were exceptionally low solar (and thus low
interplanetary) magnetic fields. Another important factor in MGA23 was the
disappearance of equatorial and low latitude coronal holes and the
appearance of midlatitude coronal holes. The location of the holes relative
to the ecliptic plane led to low solar wind speeds and low IMF (Bz)
variances (σBz2) and normalized variances (σBz2/B02) at Earth, with concomitant reduced solar
wind-magnetospheric energy coupling. One result was the lowest ap indices in
the history of ap recording. The results presented here are used to comment
on the possible solar and interplanetary causes of the low geomagnetic
activity that occurred during the Maunder Minimum. |
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