Coupling of the tearing mode instability with K-H instability at the magnetopause

The coupling of the tearing mode instability with Kelvin-Helmholtz instability (K-H) at the magnetopause is studied by performing a 2-D MHD simulation. It is found that in the case that both Reynolds and magnetic Reynolds numbers are fixed, the Alfven Mach number, MA plays an essential role in determining the linear properties and nonlinear evolution of the coupled instability. If MA<0.4, the spontaneous tearing mode is dominated in the system. When 0. 4≤MA≤1, the tearing mode is apparently modified by K-H. As 1 < MA, the coupled instability, called the vortex induced tearing mode instability (VITM), appears to be intrinsically different from the conventional tearing mode instability. The long time asymptotic quasi-static state for VITM is characterized by a large scale fluid vortex together with a concurrent magnetic island.