 |
| Titel |
The presence of large sunspots near the central solar meridian at the times of major geomagnetic storms |
| VerfasserIn |
D. M. Willis, R. Henwood, F. R. Stephenson |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 27, no. 1 ; Nr. 27, no. 1 (2009-01-13), S.185-197 |
| Datensatznummer |
250016365
|
| Publikation (Nr.) |
 copernicus.org/angeo-27-185-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| A further study is made of the validity of a technique
developed by the authors to identify historical occurrences of intense
geomagnetic storms, which is based on finding approximately coincident
observations of sunspots and aurorae recorded in East Asian histories.
Previously, the validity of this technique was corroborated using scientific
observations of aurorae in Japan during the interval 1957–2004 and
contemporaneous white-light images of the Sun obtained by the Royal
Greenwich Observatory, the Big Bear Solar Observatory, the Debrecen
Heliophysical Observatory, and the Solar and Heliospheric Observatory
spacecraft. The present investigation utilises a list of major geomagnetic
storms in the interval 1868–2008, which is based on the magnitude of the
AA* magnetic index, and reconstructed solar images based on the sunspot
observations acquired by the Royal Greenwich Observatory during the shorter
interval 1874–1976. It is found that a sunspot large enough to be seen
with the unaided eye by an "experienced" observer was located reasonably
close to the central solar meridian for almost 90% of these major
geomagnetic storms. Even an "average" observer would easily achieve a
corresponding success rate of 70% and this success rate increases to
about 80% if a minority of ambiguous situations are interpreted
favourably. The use of information on major geomagnetic storms, rather than
modern auroral observations from Japan, provides a less direct corroboration
of the technique for identifying historical occurrences of intense
geomagnetic storms, if only because major geomagnetic storms do not
necessarily produce auroral displays over East Asia. Nevertheless, the
present study provides further corroboration of the validity of the original
technique for identifying intense geomagnetic storms. This additional
corroboration of the original technique is important because early
unaided-eye observations of sunspots and aurorae provide the only possible
means of identifying individual geomagnetic storms during the greater part
of the past two millennia. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|