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| Titel |
Low-frequency magnetic field fluctuations in Earth's plasma environment observed by THEMIS |
| VerfasserIn |
L. Guicking, K.-H. Glassmeier, H.-U. Auster, Y. Narita, G. Kleindienst |
| 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 ; 30, no. 8 ; Nr. 30, no. 8 (2012-08-27), S.1271-1283 |
| Datensatznummer |
250017260
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1271-2012.pdf |
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| Zusammenfassung |
| Low-frequency magnetic wave activity in Earth's plasma environment was
determined based on a statistical analysis of THEMIS magnetic field data. We
observe that the spatial distribution of low-frequency magnetic field
fluctuations reveals highest values in the magnetosheath, but the
observations differ qualitatively from observations at Venus presented in a
previous study since significant wave activity at Earth is also observed in
the nightside magnetosheath. Outside the magnetosheath the low-frequency wave
activity level is generally very low. By means of an analytical streamline
model for the magnetosheath plasma flow, we are able to investigate the
spatial and temporal evolution of wave intensity along particular streamlines
in order to characterise possible wave generation mechanisms. We observe a
decay of wave intensity along the streamlines, but contrary to the situation
at Venus, we obtain good qualitative agreement with the theoretical concept
of freely evolving/decaying turbulence. Differences between the dawn region
and the dusk region can be observed only further away from the magnetopause.
We conclude that wave generation mechanisms may be primarily attributed to
processes at or in the vicinity of the bow shock. The difference with the
observations of the Venusian magnetosheath we interpret to be the result of
the different types of solar wind interaction processes since the Earth
possesses a global magnetic field while Venus does not, and therefore the
observed magnetic wave activities may be caused by diverse magnetic field
controlled characteristics of wave generation processes. |
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