The transformation of magnetoacoustic waves into Alfvén waves inside the magnetosphere

Abstract. A mechanism for the transformation of a magnetoacoustic wave into an Alfvén wave is proposed. During the compression of the magnetosphere by the solar wind the inner edge of the plasma sheet and the contours of B=const move in different ways. In the case of asymmetrical compression, the contours of B=const will cross the inner edge of the plasma sheet. To close the drift currents - that flow in the plasma sheet along the contours of B=const - the appearance of the field-aligned currents is necessary. This appearance corresponds to the generation of the Alfvén wave.