Compressional MHD wave transport in the magnetosphere 1. Reflection and transmission across the plasmapause

Magnetohydrodynamic (MHD) wave properties in inhomogeneous plasmas such as the magnetosphere are complicated by existence of local cutoff, coupling, and dissipation. We study the transport of MHD waves when compressional waves are assumed to propagate into the plasmasphere from the outer magnetosphere. By assuming a region of the Alfven speed crest, which approximates the plasmapause region, we investigate how the initial compressional MHD wave energy is reflected, absorbed, and delivered across the plasmapause. Our results present the exact reflection, transmission, and absorption coefficients without any theoretical approximations for given frequencies and wave numbers. It is found that relatively strong absorption of compressional waves occurs where the frequency ranges from the local resonant condition to the cutoff condition at the maximum of the Alfven speed crest. We compare and discuss the behavior of compressional waves in our results with previous observations.