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| Titel |
Plasma mixing and transport caused by the three-dimensional development of the Kelvin-Helmholtz instability |
| VerfasserIn |
Takuma Nakamura, William Daughton, Homa Karimabadi, Stefan Eriksson |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103833
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| Publikation (Nr.) |
 EGU/EGU2015-3249.pdf |
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| Zusammenfassung |
| The Kelvin-Helmholtz instability (KHI) is a key process for the transport of solar wind
plasma into the Earth’s magnetosphere across the magnetopause. When both magnetic and
velocity shears coexists within a boundary as commonly seen at the magnetopause, the
resulting KHI leads to generation of vortices and subsequent triggering of magnetic
reconnection. Our recent 3D fully kinetic simulations of this vortex-induced reconnection
(VIR) process for symmetric boundary layers demonstrated the copious formation of oblique
magnetic flux ropes, which leads to a rapid mixing of the plasma within the vortex layer.
THEMIS observations at the dusk-flank magnetopause indeed show similar features of
flux ropes between observed KH vortices. More recently, we performed additional
3D fully kinetic simulations considering the effects of density and temperature
asymmetries, which also commonly exist across the magnetopause. Past 2D simulations
have shown that such asymmetries can lead to an excitation of secondary KH and
Rayleigh-Taylor (RT) instabilities along the edge of the vortex in the absence of a
finite magnetic field component (Bk) parallel to the k-vector of the KHI. Since
Bk is expected to be finite at the magnetopause, here we explore the effect of Bk
on the secondary KH/RT instabilities in 3D. We find that the suppression of the
secondary instabilities due to Bk is an artifact of the 2D simulations, whereas in
3D the instabilities can grow over a range of oblique angles even when there is a
finite Bk. These secondary instabilities give rise to turbulence, which gradually
transports the solar wind plasma originally stored within the flow vortices deep into the
magnetosphere. Simple estimates suggest that the reconnection-induced rapid mixing and the
turbulent-induced gradual transport processes may contribute significantly to the formation of
the Earth’s low-latitude boundary layer (LLBL) and the cold-dense plasma sheet
(CDPS) during prolonged periods of northward interplanetary-magnetic-field (IMF). |
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