HR: 1340h
AN: SM43C-1237    [Abstracts]
TI: Three-dimensional nonlinear evolution of the Kelvin-Helmholtz instability as an energy transport mechanism from the solar wind to the ionosphere
AU: * Matsumoto, Y
EM: ymatumot@stelab.nagoya-u.ac.jp
AF: The 21st Century COE Program, Graduate School of Environmental Studies, Nagoya University, Honohara 3-13, Toyokawa, 442-8507 Japan
AU: Seki, K
EM: seki@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Honohara 3-13, Toyokawa, 442-8507 Japan
AB: The Kelvin-Helmholtz instability (KHI) has been considered to be a direct transport mechanism of the solar wind plasma across the low-latitude magnetopause (e.g., Matsumoto and Hoshino, 2004). The observational evidences indicate that the low latitude boundary of the flanks are KH unstable and the KHI must be an important process for transferring energy, momentum and particles to the magnetotail during times of prolonged northward IMF. In addition, the ground-based and the satellite observations have shown the vortical patterns of aurora and have indicated that the energy transport from the solar wind to the ionosphere has been also operative in association with the mass transport to the magnetosphere. Motivated by those observational requirements, the three-dimensional ideal MHD simulation of the KHI has been conducted for understanding the solar wind energy transfer to the ionosphere simultaneously to the magnetosphere.
The set of ideal MHD equations are solved by the fractional step approach which consists of the advection phase by CIP method (Yabe et al., 1991) and the non-advection phase by the 3rd order Adams-Moulton predictor-corrector method. The resultant three-dimensional evolution of the KHI possesses new signatures that cannot be obtained in the two dimensional evolution. It was shown that the vortex core was susceptible to the three-dimensional secondary instability even for a strong transverse magnetic field case (β=0.1). To understand its nature, we modeled the one-dimensional axisymmetric vortex core, where the centrifugal force was balanced with the gradient in the total pressure. Then we analyzed the linear response of the system. The resultant dispersion relation had a form similar to that of the Balbus-Hawley instability (Balbus and Hawley, 1991), while some differences arose due to the assumption of the strong magnetic field and the compressibility in the present study. The dispersion relation indicated that the KH vortex core was unstable to the instability whose growth rate and the wave length of the fastest growing mode were the order of those of the KHI. We will present the possibility of the energy transport mechanism from the solar wind to the ionosphere through this secondary instability.

References
Y. Matsumoto and M.Hoshino, Geophys. Res. Lett., 2004
T. Yabe et al., Comput. Phys. Commun., 1991
S. A. Balbus and J. F. Hawley, ApJ, 1991
DE: 2724 Magnetopause and boundary layers
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2753 Numerical modeling
DE: 2784 Solar wind/magnetosphere interactions
DE: 7863 Turbulence (4490)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005