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| Titel |
Relation between substorm characteristics and rapid temporal variations of the ground magnetic field |
| VerfasserIn |
A. Viljanen, E. I. Tanskanen, A. Pulkkinen |
| 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 ; 24, no. 2 ; Nr. 24, no. 2 (2006-03-23), S.725-733 |
| Datensatznummer |
250015506
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| Publikation (Nr.) |
 copernicus.org/angeo-24-725-2006.pdf |
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| Zusammenfassung |
| Auroral substorms are one of the major causes of large geomagnetically
induced currents (GIC) in technological systems. This study deals with
different phases of the auroral substorm concerning their severity from the
GIC viewpoint. Our database consists of 833 substorms observed by the IMAGE
magnetometer network in 1997 (around sunspot minimum) and 1999 (rising phase
of the sunspot cycle), divided into two classes according to the Dst index:
non-storm (Dst>-40 nT, 696 events) and storm-time ones (Dst<-40 nT, 137
events). The key quantity concerning GIC is the time derivative of the
horizontal magnetic field vector (dH/dt) whose largest values
during substorms occur most probably at about 5 min after the onset at
stations with CGM latitude less than 72 deg. When looking at the median
time of the occurrence of the maximum dH/dt after the expansion
onset, it increases as a function of latitude from about 15 min at CGM
lat=56 deg to about 45 min at CGM lat=75 deg for non-storm substorms. For
storm-time events, these times are about 5 min longer. Based on
calculated ionospheric equivalent currents, large dH/dt occur
mostly during the substorm onset when the amplitude of the westward
electrojet increases rapidly. |
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