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| Titel |
Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study |
| VerfasserIn |
P. T. I. Eriksson, L. G. Blomberg, A. D. M. Walker, K.-H. Glassmeier |
| 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 ; 23, no. 7 ; Nr. 23, no. 7 (2005-10-14), S.2679-2686 |
| Datensatznummer |
250015340
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| Publikation (Nr.) |
 copernicus.org/angeo-23-2679-2005.pdf |
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| Zusammenfassung |
Three ULF wave events, all occurring in the dayside magnetopshere
during magnetically quiet times, are studied using the Cluster
satellites. The multi-point measurements obtained from Cluster are
used to determine the azimuthal wave number for the events by
means of the phase shift and the azimuthal separation between the
satellites. Also, the polarisation of the electric and magnetic
fields is examined in a field-aligned coordinate system, which, in
turn, gives the mode of the oscillations. The large-inclination
orbits of Cluster allow us to examine the phase relationship
between the electric and magnetic fields along the field lines.
The events studied have large azimuthal wave numbers (m~100),
two of them have eastward propagation and all are in the
poloidal mode, consistent with the large wave numbers. We also use
particle data from geosynchronous satellites to look for
signatures of proton injections, but none of the events show any
sign of enhanced proton flux. Thus, the drift-bounce resonance
instability seems unlikely to have played any part in the
excitation of these pulsations. As for the drift-mirror
instability we conclude that it would require an unreasonably high
plasma pressure for the instability criterion to be satisfied.
Keywords. Ionosphere (Wave propagation) – Magnetospheric
physics (Plasma waves and instabilities; Instruments
and techniques) |
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