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| Titel |
Study of the longitudinal expansion velocity of the substorm current wedge |
| VerfasserIn |
A. Belehaki, I. Tsagouri, H. Mavromichalaki |
| 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 ; 16, no. 11 ; Nr. 16, no. 11, S.1423-1433 |
| Datensatznummer |
250013539
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| Publikation (Nr.) |
 copernicus.org/angeo-16-1423-1998.pdf |
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| Zusammenfassung |
In this work we examine simultaneous
observations from the two geosynchronous satellites GOES-5 and GOES-6 located at
282°E and 265°E respectively, and from middle and low latitude ground
observatories located within 250°E and 294°E geographic longitude, during
isolated substorms of moderate activity. The spatial distribution of our
observation points allows us to make a detailed study of the azimuthal expansion
of the substorm current wedge. The data analysis shows evidence that the
substorm initiation and development mechanism include the cross-tail current
diversion/ disruption, the substorm current wedge formation and the azimuthal
expansion of the inner plasma sheet. The triggering mechanism is initially
confined in a longitudinally narrow sector, estimated to be less than 15° and
located very close to local midnight to the east or to the west. The current
disruption region expands both eastward and westward in the magnetotail, so that
the location of major field-aligned currents flowing into the ionosphere shifts
successively eastward, and the location of the currents flowing out of the
ionosphere shifts successively westward. Evidence was found that the
perturbation travels toward the west with velocities greater than those
expanding the wedge eastward. The drastic decrease of the velocity with the
azimuthal distance from the location of the disturbance initiation, i.e., the
onset sector, indicates that the energy release is a very localized phenomenon.
Finally, the transient D perturbation observed by the geosynchronous satellites
suggests that the field-aligned currents forming the wedge have a longitudunally
limited extent.
Key words. Magnetospheric physics (current systems;
magnetosphere-ionosphere interactions) |
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