Magnetosonic resonances in the magnetospheric plasma

Abstract

A problem of coupling between fast and slow magnetosonic waves in Earth’s magnetosphere (magnetosonic resonance) is examined. Propagation both slow magnetosonic wave and Alfven wave can easily be canalized along the magnetic field line direction. The main difference between the two is that slow magnetosonic waves dissipate strongly due to their interaction with the background plasma ions, whose temperature is above the electron temperature. In Earth’s magnetosphere, however, there is a region where the dissipation of slow magnetosonic waves can be weak—the inner plasmasphere. The slow magnetosonic waves generated there can be registered directly. In other regions, with strong dissipation of slow magnetosonic waves, their signature may be detected through their impact on the Alfven resonance at frequencies for which the resonant Alfven and slow magnetosonic waves exist simultaneously in the magnetosphere. Owing to their strong coupling with the background plasma ions, resonant slow magnetosonic waves can transfer the energy and impulse from the solar wind to the magnetospheric plasma ions via fast magnetosonic waves penetrating into the tail lobes. A problem of resonant conversion of fast magnetosonic waves into slow magnetosonic oscillations in a magnetosphere with dipole-like magnetic field is also examined.