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| Titel |
The correlation between solar and geomagnetic activity – Part 2: Long-term trends |
| VerfasserIn |
Z. L. Du |
| 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. 8 ; Nr. 29, no. 8 (2011-08-05), S.1341-1348 |
| Datensatznummer |
250017068
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| Publikation (Nr.) |
 copernicus.org/angeo-29-1341-2011.pdf |
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| Zusammenfassung |
| Using lag-correlation function analysis, the correlation
coefficient at zero lag (r0), the maximum (rm)
and the corresponding lag time (Lm) between solar
(Rz) and geomagnetic (aa) activity for a 528-month
(44-year) running time window are shown to vary in a declining,
declining and rising secular trend, respectively, before 1958.
However, these trends changed since 1958 with a rising secular
trend in both r0 and rm and without a significant
trend in Lm, probably related to a periodicity
longer than 140 years. An odd-numbered solar cycle tends to show a
higher correlation and a shorter lag time between Rz
and aa than the previous even-numbered one, suggesting a 2-cycle
periodicity superimposed on secular trends. An even-numbered Hale
cycle tends to show a higher correlation and a shorter lag time
between Rz and aa than the previous odd-numbered
one, suggesting a 4-cycle periodicity superimposed on secular
trends. The variations in the correlations may be related to the
non-linearity between Rz and aa, and the
decreasing trend in the correlation (r0) is not exclusively
caused by the increasing trend in the lag time of aa to
Rz. These results represent an observational
constraint on solar-dynamo models and can help us gain a better
understanding of the long-term evolution of solar activities. In
applications, therefore, cautions must be taken when using the
correlation for molding the dynamical process of the Sun and for
predicting solar activities. |
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