Theory of azimuthally small-scale hydromagnetic waves in the axisymmetric magnetosphere with ®nite plasma pressure


The structure of monochromatic MHD-waves with large azimuthal wave number m 1 in a twodimensional model of the magnetosphere has been investigated. A joint action of the ®eld line curvature, ®nite plasma pressure, and transversal equilibrium current leads to the phenomenon that waves, standing along the ®eld lines, are travelling across the magnetic shells. The wave propagation region, the transparency region, is bounded by the poloidal magnetic surface on one side and by the resonance surface on the other. In their meaning these surfaces correspond to the usual and singular turning points in the WKB-approximation, respectively. The wave is excited near the poloidal surface and propagates toward the resonance surface where it is totally absorbed due to the ionospheric dissipation. There are two transparency regions in a ®nite-beta magnetosphere, one of them corresponds to the Alfve n mode and the other to the slow magnetosound mode.


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