HR: 08:00h
AN: SM21C-01    [Abstracts]
TI: Nonlinear Evolution of Kelvin-Helmholtz Instability in MHD Plasma
AU: Lai, S
EM: lucky@jupiter.ss.ncu.edu.tw
AF: National Central University, Institute of Space Science, National Central University , Chung-Lu, 320-01 Taiwan
AU: * Lyu, L
EM: lyu@jupiter.ss.ncu.edu.tw
AF: National Central University, Institute of Space Science, National Central University , Chung-Lu, 320-01 Taiwan
AB: Kelvin-Helmholtz (K-H) instabilities at a magnetohydrodynamic (MHD) tangential discontinuity (TD) are studied by means of two-dimensional MHD simulation. Our simulation results indicate that nonlinear evolution of MHD surface wave at TD depends on the fast-mode Mach numbers of the surface wave on two sides of the TD. When the fast-mode Mach numbers of the surface wave on both sides of the TD are less than 1, K-H instability can grow into vortices or kink-type surface wave, depending on the orientation of the ambient magnetic field. When the fast-mode Mach number on either side of the TD is greater than 1, nonlinear fast-mode plane waves are developed from the ridges on the surface wave. A theoretical model based on magnetosonic-cone formation is proposed to explain the formation of these nonlinear plane waves in high-Mach-number K-H instability. Mach angle of magnetosonic cone is derived as a function of Mach number, orientation of ambient magnetic field, and plasma beta of the background medium. Flaring angles of these nonlinear plane waves obtained in our simulations are in good agreement with the Mach angles predicted by our theoretical model. Nonlinear evolution of K-H instability generated by a fast jet flow after magnetic reconnection will also be presented. Application of our results to magnetopause and nonlinear waves in magnetosheath and magnetosphere will be discussed.
DE: 7839 Nonlinear phenomena
DE: 7843 Numerical simulation studies
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2728 Magnetosheath
DE: 2752 MHD waves and instabilities
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting