On the spatial structure and dispersion of slow magnetosonic modes coupled with Alfven modes in planetary magnetospheres due to field line curvature

摘要

The structure of the slow mode coupled with Alfven mode in the axially symmetric magnetosphere is studied in the paper. Due to the coupling, the siow magnetosonic wave gets dispersion across magnetic shells and becomes not strictly guided. The slow mode is found to be captured between the resonant and cutoff surfaces, where the wave vector radial component goes to infinity and to zero, accordingly. The resonant surface is farther from the Earth than the cutoff surface. The slow mode resonance frequency is much lower than the Alfven resonance frequency due to small value of the sound velocity near the equator. The maximum of the slow mode amplitude expressed in terms of the parallel magnetic field is concentrated near the equator, but expressed in hydromagnetic terms is concentrated near the ionospheres.