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| Titel |
The use of interplanetary scintillation maps in the prediction of geomagnetic activity |
| VerfasserIn |
E. A. Lucek, T. D. G. Clark |
| 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 ; 14, no. 2 ; Nr. 14, no. 2, S.131-138 |
| Datensatznummer |
250012163
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| Publikation (Nr.) |
 copernicus.org/angeo-14-131-1996.pdf |
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| Zusammenfassung |
| Interplanetary scintillation (IPS), the
twinkling of small angular diameter radio sources, arises from the interaction
of the signal with small-scale plasma irregularities in the solar wind. The
technique may be used to sense remotely the near-Earth heliosphere and has
potential for tracking large-scale interplanetary disturbances from close to the
Sun to the Earth. Such observations might be useful within routine geomagnetic
forecasts, and we use data from the Mullard Radio Astronomy Observatory to test
this suggestion. A forecast was based on the visual evaluation of each daily
map. If an IPS event was observed then we proposed that any associated
geomagnetic activity would occur either on that day, or during the following two
days. We consider the success of these forecasts in predicting days when either
an SSC/SI or an Ap value exceeding 30 were recorded. The identification
of IPS events is necessarily subjective and so two observers compiled
independent events lists, and the results were compared. Approximately half of
the IPS events in each list were followed by a geomagnetic signature but
comparison of the two lists showed that different days were being chosen. We
also found that the forecasts had very high false alarm rates. Since IPS is
sensitive to a volume we did not expect all events to be associated with a
geomagnetic signature. However, the technique failed to forecast a large
proportion of geomagnetic events and the association between IPS events and
geomagnetic activity is not much better than would be expected by chance.
Comparing the IPS forecasts with forecasts of Ap released by the Space
Environment Services Center (SESC) we found that SESC correctly predicted a
similar proportion of days when Ap\geq30, but that the performance was
significantly better than would be expected by chance, and had a much lower
false alarm rate. We conclude that these IPS data cannot be used alone to
produce reliable geomagnetic activity forecasts. |
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