The Great Geomagnetic Storm of 9 November 1991: Origin in a Disappearing Solar Filament
Abstract
The largest geomagnetic storms are characteristically associated with major solar flares. The great storm of 9 November 1991 (Dst = -375 nT) provides an exception to this rule of thumb. It is ranked tenth of the largest Dst storms from 1932-2002, surpassing in intensity such well known events as 14 July 1982 and 16 July 2000. The November 1991 storm can be traced to a large disappearing solar filament from the southeast quadrant late on 5 November. The filament was located outside of an active region and its disappearance was well observed in both H-alpha and soft X-rays. The associated long-duration 1-8 Angstrom event had a C5 peak. This solar-terrestrial event indicates that neither a large complex active region nor an intense solar flare is a requirement for even first rank geomagnetic storms, thus providing insight to the physics of such events while making their prediction more difficult.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2006
- Bibcode:
- 2006AGUSMSH43A..06C
- Keywords:
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- 7513 Coronal mass ejections (2101);
- 7519 Flares;
- 7531 Prominence eruptions;
- 7954 Magnetic storms (2788)