Standing Alfvén waves with m ≫ 1 in an axisymmetric magnetosphere excited by a non-stationary source

Abstract. As a continuation of our earlier paper, we consider here the case of the excitation of standing Alfvén waves by a source of the type of sudden impulse. It is shown that, following excitation by such a source, a given magnetic shell will exhibit oscillations with a variable frequency which increases from the shell's poloidal to toroidal frequency. Simultaneously, the oscillations will also switch over from poloidally (radially) to toroidally (azimuthally) polarized. With a reasonably large attenuation, only the start of this process, the stage of poloidal oscillations, will be observed in the ionosphere.

Key words. Ionosphere-magnetosphere interactions · Wave propagation · MHD waves and instabilities