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| Titel |
Formation of a broad plasma mixing layer by forward and inverse energy cascades of the Kelvin-Helmholtz instability |
| VerfasserIn |
Yosuke Matsumoto, Kanako Seki |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034863
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| Zusammenfassung |
| The formation mechanism of the LLBL in the magnetosphere is a long standing issue in the
magnetospheric physics and the Kelvin-Helmholtz instability (KHI) is one of the candidate
mechanisms responsible for its formation. In this presentation, 2D MHD simulation of the
KHI in a highly asymmetric density layer shows that rapid formation of a broad plasma
mixing layer can be achieved by forward and inverse energy cascades of the KHI. The
forward cascade is triggered by the growth of the secondary Rayleigh-Taylor instability
[Matsumoto and Hoshino, JGR, 2006] excited during the nonlinear evolution of the KHI. The
resultant turbulent evolution enhances the mixing process. The inverse cascade is
accomplished by nonlinear mode couplings among the KH unstable modes. Due
to the nonlinear mode couplings, the growth of the largest vortex allowed in the
system reached 3.7 times the linear growth rate. By a combination of the secondary
instability and the rapid growth of the large scale vortex, we show that a plasma mixing
layer of a spatial scale of 7 RE is formed within 10 minutes, when 1000 km and
400 km s-1 are adopted for the shear half width and the solar wind flow speed,
respectively. The results suggest that the mechanism proposed here can be responsible
for the formation of the LLBL in the magnetosphere for a purely northward IMF
case. |
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