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| Titel |
Westward moving dynamic substorm features observed with the IMAGE magnetometer network and other ground-based instruments |
| VerfasserIn |
H. Lühr, A. Aylward, S. C. Bucher, A. Pajunpää, K. Pajunpää, T. Holmboe, S. M. Zalewski |
| 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. 4 ; Nr. 16, no. 4, S.425-440 |
| Datensatznummer |
250013244
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| Publikation (Nr.) |
 copernicus.org/angeo-16-425-1998.pdf |
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| Zusammenfassung |
We present the ground signatures of dynamic
substorm features with particular emphasis on the event interpretation
capabilities provided by the IMAGE magnetometer network. This array covers the
high latitudes from the sub-auroral to the cusp/cleft region. An isolated
substorm on 11 Oct. 1993 during the late evening hours exhibited many of
well-known features such as the Harang discontinuity, westward travelling surge
and poleward leap, but also discrete auroral forms, known as auroral streamers,
appeared propagating westward along the centre of the electrojet. Besides the
magnetic field measurements, there were auroral observations and plasma flow and
conductivity measurements obtained by EISCAT. The data of all three sets of
instruments are consistent with the notion of upward field-aligned currents
associated with the moving auroral patches. A detailed analysis of the
electrodynamic parameters in the ionosphere, however, reveals that they do not
agree with the expectations resulting from commonly used simplifying
approximations. For example, the westward moving auroral streamers which are
associated with field-aligned current filaments, are not collocated with the
centres of equivalent current vortices. Furthermore, there is a clear
discrepancy between the measured plasma flow direction and the obtained
equivalent current direction. All this suggests that steep conductivity
gradients are associated with the transient auroral forms. Also self-induction
effects in the ionosphere may play a role for the orientation of the plasma
flows. This study stresses the importance of multi-instrument observation for a
reliable interpretation of dynamic auroral processes.
Keywords. Ionosphere (Auroral ionosphere; Electric
fields and currents; Ionosphere-magnetosphere interactions). |
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