TRANSMISSION OF MAGNETOHYDRODYNAMIC WAVES THROUGH THE ROTATIONAL DISCONTINUITY AT THE EARTHS MAGNETOPAUSE

Reflection and transmission of small-amplitude magnetohydrodynamic (MHD) waves of solar-wind origin through the earth's open magnetopause are studied. The open magnetopause with a nonzero normal component of magnetic field is assumed to be a rotational discontinuity. For any of the incident waves, there is one reflected wave (fast magnetosonic wave) and five transmitted waves (one fast magnetosonic wave, two slow magnetosonic waves, one Alfven wave, and one entropy wave). In this paper, cases with different incident waves, i. e. , Alfven wave, fast magnetosonic wave, forward slow magnetosonic wave and entropy wave are studied. It is found that depending on the type of incident wave, the incident angle and the orientation of the ambient magnetic field, the amplitudes of the emanating waves can be amplified. The research findings also suggest that the transmission of MHD waves across the rotational discontinuity at the earth's magnetopause can be an important mechanism for the energy transfer from the solar wind into the magnetosphere.