Linear and nonlinear Alfven wave propagation in compressible MHD plasmas

Evolution of both low-frequency harmonic Alfven wave train and Alfven solitary wave is studied by using the compressible MHD fluid model. A critical point is found at which linear wave theory should be replaced by a nonlinear one. A small, but finite amplitude Alfven solitary wave is numerically found. The head-on collision between an Alfven wave train and an Alfven solitary wave is also numerically investigated. An interesting result is that there is no phase shift for both colliding waves which is different from that between two KdV solitary waves.