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| Titel |
Severe geomagnetic storms and Forbush decreases: interplanetary relationships reexamined |
| VerfasserIn |
R. P. Kane |
| 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 ; 28, no. 2 ; Nr. 28, no. 2 (2010-02-09), S.479-489 |
| Datensatznummer |
250016778
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| Publikation (Nr.) |
 copernicus.org/angeo-28-479-2010.pdf |
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| Zusammenfassung |
| Severe storms (Dst) and Forbush decreases (FD)
during cycle 23 showed that maximum negative Dst magnitudes usually occurred
almost simultaneously with the maximum negative values of the Bz component
of interplanetary magnetic field B, but the maximum magnitudes of negative
Dst and Bz were poorly correlated (+0.28). A parameter Bz(CP) was calculated
(cumulative partial Bz) as sum of the hourly negative values of Bz from the
time of start to the maximum negative value. The correlation of negative Dst
maximum with Bz(CP) was higher (+0.59) as compared to that of Dst with Bz
alone (+0.28). When the product of Bz with the solar wind speed V (at the
hour of negative Bz maximum) was considered, the correlation of negative Dst
maximum with VBz was +0.59 and with VBz(CP), 0.71. Thus, including V
improved the correlations. However, ground-based Dst values have a
considerable contribution from magnetopause currents (several tens of nT,
even exceeding 100 nT in very severe storms). When their contribution is
subtracted from Dst(nT), the residue Dst* representing true ring current
effect is much better correlated with Bz and Bz(CP), but not with VBz or
VBz(CP), indicating that these are unimportant parameters and the effect of
V is seen only through the solar wind ram pressure causing magnetopause
currents. Maximum negative Dst (or Dst*) did not occur at the same hour as
maximum FD. The time evolutions of Dst and FD were very different. The
correlations were almost zero. Basically, negative Dst (or Dst*) and FDs are
uncorrelated, indicating altogether different mechanism. |
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