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| Titel |
MHD aspect of current sheet oscillations related to magnetic field gradients |
| VerfasserIn |
N. V. Erkaev, V. S. Semenov, I. V. Kubyshkin, M. V. Kubyshkina, H. K. Biernat |
| 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 ; 27, no. 1 ; Nr. 27, no. 1 (2009-01-23), S.417-425 |
| Datensatznummer |
250016382
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| Publikation (Nr.) |
 copernicus.org/angeo-27-417-2009.pdf |
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| Zusammenfassung |
| One-fluid ideal MHD model is applied for description of
current sheet flapping disturbances appearing due to a gradient
of the normal magnetic field component. The wave modes are
studied which are associated to the flapping waves observed in
the Earth's magnetotail current sheet. In a linear
approximation, solutions are obtained for model profiles of the
electric current and plasma densities across the current sheet,
which are described by hyperbolic functions. The flapping
eigenfrequency is found as a function of wave number. For the
Earth's magnetotail conditions, the estimated wave group speed
is of the order of a few tens kilometers per second. The
current sheet can be stable or unstable in dependence on the
direction of the gradient of the normal magnetic field
component. The obtained dispersion function is used for
calculation of the flapping wave disturbances, which are
produced by the given initial Gaussian perturbation at the
center of the current sheet and propagating towards the flanks.
The propagating flapping pulse has a smooth leading front, and
a small scale oscillating trailing front, because the short
wave oscillations propagate much slower than the long wave
ones. |
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