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| Titel |
Climatology of rapid geomagnetic variations at high latitudes over two solar cycles |
| VerfasserIn |
A. Viljanen, E. Tanskanen |
| 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. 10 ; Nr. 29, no. 10 (2011-10-11), S.1783-1792 |
| Datensatznummer |
250017106
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| Publikation (Nr.) |
 copernicus.org/angeo-29-1783-2011.pdf |
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| Zusammenfassung |
| We investigate the characteristics of rapid geomagnetic variations at high
latitudes based on the occurrence of large time derivatives of the horizontal
magnetic field (dH/dt exceeding 1 nT s−1). Analysis of IMAGE
magnetometer data from North Europe in 1983–2010, covering more than two
solar cycles, confirms and specifies several previous findings. We show that
dH/dt activity is high around the midnight and early morning
hours, and nearly vanishes at noon and early afternoon. This happens during
all seasons, although the midnight maximum is nearly invisible during summer.
As indicated by modelled ionospheric equivalent currents, large
dH/dt values occur predominantly during westward ionospheric
electrojets. Before and around midnight, dH/dt tends to be
north-south oriented, whereas in the morning hours, its direction is more
west-east directed. dH/dt tends to be more strictly north-south
oriented during winter than other seasons. The seasonal occurrence of large
dH/dt values is similar to the variation of the maximum amplitude
of westward equivalent currents. The yearly fraction of east-west directed
large dH/dt vectors at the Kilpisjärvi station (MLAT 65.88) varies
from 31 to 47 % without any clear correlation with the general geomagnetic
activity nor with the yearly averages of solar wind parameters. |
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