The compressible evolution of the super-Alfvenic magnetized wake

The effects of compressibility on the linear and nonlinear properties of th e magnetized wake are examined, with an emphasis on the high speed flow sit uation. It is found that compressibility can modify properties of this syst em previously identified for the incompressible case. Of particular interes t is an investigation of how the properties of the magnetized wake vary wit h the sonic Mach number. It is found that, in general, the growth rates of the unstable sinuous and varicose modes decrease with increasing Mach numbe r and with increasing Alfven number. However, at high sonic Mach numbers th e varicose modes can have a growth rate which increases as the spanwise wav e number increases, a significant difference from the incompressible case. The linear compressible equations are solved by a Chebyshev collocation tec hnique. Nonlinear computations based on a finite volume method are also pre sented. Growth rates computed by both codes in the linear regime are in exc ellent agreement. At long times the system relaminarizes to an overall acce lerated and broadened wake channel. It is found that variations in the Mach and Alfven numbers have a strong affect on the evolution of the magnetized wake, e.g., for high M fast magnetosonic shocks are observed to develop. ( C) 2001 American Institute of Physics.