MHD WAVE CONVERSION IN PLASMA WAVE-GUIDES

A theoretical approach to the consideration of coupling between Alfven and compressional modes in two-dimensionally inhomogeneous plasma has been developed. The conversion of a compressional mode, propagating a long a high-density layer perpendicular to the magnetic field, into le aking shear Alfven waves has been considered. The wave spatial structu re along the layer is described in WKB approximation. A compressional- type disturbance effectively emitts Alfven waves when a local resonant condition within the layer is fulfilled. In contrast with the common field line resonance theory, the excited Alfven modes are assumed to b e running away waves but not standing oscillations. The physical situa tions that correspond to the considered model can be met in the outer near-equatorial magnetosphere, in the exterior cusp region, and in the other magnetospheres such as Jupiter and Saturn.