HR: 1340h
AN: SM43C-1236    [Abstracts]
TI: Three-dimensional MHD simulations of Kelvin-Helmholtz instability in a magnetotail flank-like geometry
AU: * Takagi, K
EM: ktakagi@geo.titech.ac.jp
AU: Hasegawa, H
EM: hiroshih@geo.titech.ac.jp
AU: TanDokoro, R
EM: rtdokoro@geo.titech.ac.jp
AU: Nakamura, T
EM: takuma@geo.titech.ac.jp
AU: Fujimoto, M
EM: fujimoto@geo.titech.ac.jp
AB: We have performed three-dimensional MHD simulations to investigate the Kelvin-Helmholtz vortices at the interface between the tail-flank of the magnetosphere and the magnetosheath. The simulation domain is divided into three regions; plasmasheet (K-H unstable), tail lobe region (K-H stable) and magnetosheath (K-H unstable). The results show that the K-H instability can grow to form a highly rolled-up vortex even when the plasma sheet (unstable layer) thickness is as small as 1.3 times the wavelength of most unstable mode. Furthermore, we found that the low-density, plasma sheet plasma is accelerated tailward to a speed higher than the magnetosheath flow, when it penetrates into the high-density magnetosheath region within the vortex. This overshoot tailward flow is seen only when a K-H vortex is rolled up and, importantly, can be found even from single-spacecraft observations. Thus the signature can be taken as the smoking gun evidence of a rolled-up vortex in such observations. In real situations, the vortices may coalesce, so we have also performed simulations which can treat coalescence of two K-H vortices. In the same plasma sheet thickness (1.3 times the wavelength) case, it is found that two vortices can coalesce and, as a result, the low-density plasma is accelerated more strongly. In addition, the volume of the simulation domain in which the above overshoot tailward flow is detected increases when the vortices coalesce. We investigate how this volume and coalescence of vortices depend on the plasma sheet thickness, to understand the role of the coalescense in the tail flank and to see if the overshoot flow can stand as the robust indicator of the rolled-up vortex.
DE: 2724 Magnetopause and boundary layers
DE: 2740 Magnetospheric configuration and dynamics
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2753 Numerical modeling
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005