MAGNETOSPHERIC CAVITY RESONANCE OSCILLATIONS WITH ENERGY-FLOW ACROSS THE MAGNETOPAUSE

We discuss the condition for the presence of a magnetospheric global o scillation having the properties of a cavity resonance oscillation by using a numerical method and assuming that the magnetopause is not a p erfect reflector. The cavity resonance oscillation occurs when there i s a plasmaspheric trough of the Alfven speed. The plasmaspheric cavity resonance oscillation is evanescent in the outer magnetosphere, where the Alfven speed is larger than in the plasmasphere. The plasmaspheri c mod is not completely confined within the plasmasphere, but can tunn el into the outer magnetosphere and have finite amplitude at the magne topause. The nonzero electromagnetic field perturbation at the magneto pause leads to leakage of the Poynting flux across the magnetopause, a nd the plasmaspheric cavity resonance oscillation is damped by the esc aping flux. The perturbations of the damped cavity resonance oscillati on exhibit phase shift toward the magnetopause, which does not imply p ropagation of the wave.