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| Titel |
Are our ideas about Dst correct? |
| VerfasserIn |
A. Grafe |
| 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 ; 17, no. 1 ; Nr. 17, no. 1, S.1-10 |
| Datensatznummer |
250013640
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| Publikation (Nr.) |
 copernicus.org/angeo-17-1-1999.pdf |
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| Zusammenfassung |
The idea of two separate storm time ring
currents, a symmetric and an asymmetric one has accepted since the 1960s. The
existence of a symmetric equatorial ring current was concluded from Dst.
However, the asymmetric development of the low-latitude geomagnetic disturbance
field during storms lead to the assumption of the real existence of an
asymmetric ring current. I think it is time to inquire whether this conception
is correct. Thus, I have investigated the development of the low-latitude
geomagnetic field during all the magnetic local times under disturbed and quiet
conditions. The storm on February 6–9, 1986 and a statistical analysis of many
storms has shown that the asymmetry does not vanish during the storm recovery
phase. The ratio between the recovery phase asymmetry and the main phase
asymmetry is low only for powerful storms. Storms of moderate intensity show the
opposite. The global picture of the field evolution of the February storm shows
clear differences at different local times. For instance the main phase and
recovery phase start time does not coincide with Dst. Also the ring
current decay is not the same at different local times. Therefore, Dst
gives an incorrect picture of the field development. Moreover, asymmetry does
not disappear during international quiet days as the investigation of the
low-latitude geomagnetic field shows. Considering all these observations, I
think we must revise our ideas about the ring current. In my opinion only one
ring current exists and this is an asymmetric one. This asymmetry increases
during storms and develops rather fast to more or less symmetric conditions.
However, in no case is it justified to conclude from Dst that a symmetric
ring current exists.
Key words. Magnetospheric physics (current systems;
magnetospheric configuration and dynamics; storms and substorms) |
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