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| Titel |
Radial dependence of foreshock cavities: a case study |
| VerfasserIn |
D. G. Sibeck, K. Kudela, T. Mukai, Z. Nemecek, J. Safrankova |
| 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 ; 22, no. 12 ; Nr. 22, no. 12 (2004-12-22), S.4143-4151 |
| Datensatznummer |
250015080
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| Publikation (Nr.) |
 copernicus.org/angeo-22-4143-2004.pdf |
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| Zusammenfassung |
We present a case study of Geotail, Interball-1, IMP-8, and
Wind observations of density and magnetic field strength cavities excavated
by the enhanced pressures associated with bursts of energetic ions in the
foreshock. Consistent with theoretical predictions, the pressure of the
energetic ions diminishes rapidly with upstream distance due to a decrease
in the flux of energetic ions and a transition from near-isotropic to
streaming pitch angle distributions. Consequently, the cavities can only be
observed immediately upstream from the bow shock. A comparison of conditions
upstream from the pre- and post-noon bow shock demonstrates that foreshock
cavities introduce perturbations into the oncoming solar wind flow with
dimensions smaller than those of the magnetosphere. Dayside geosynchronous
magnetic field strength variations observed by GOES-8 do not track the
density variations seen by any of the spacecraft upstream from the bow shock
in a one-to-one manner, indicating that none of these spacecraft observed
the precise sequence of density variations that actually struck the subsolar
magnetopause.
Key words. Interplanetary physics (energetic particles;
planetary bow shocks) – Magnetospheric physics (solar
wind-magnetosphere interactions) |
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