A strongly nonlinear Alfvenic pulse in a transversely inhomogeneous medium

We investigate the interaction of a plane, linearly polarized, Alfvenic pulse with a one-dimensional, perpendicular to the magnetic field, plasma density inhomogeneity in the strongly nonlinear regime. Our numerical study of the full MHD equations shows that: (i) Plasma density inhomogeneity substantially enhances (by about a factor of 2) the generation of longitudinal compressive waves. (ii) Attained maximal values of the generated transverse compressive perturbations are insensitive to the strength of the plasma density inhomogeneity, plasma beta and the initial amplitude of the Alfven wave. Typically, they reach about 40% of the initial Alfven wave amplitude. (iii) Attained maximal values of the generated relative density perturbations are within 20-40% for 0.5 less than or equal to beta less than or equal to 2.0. They depend upon plasma beta strongly; and scale almost linearly with the initial Alfven wave amplitude.