Field-aligned structure of poloidal Alfvén waves in a finite pressure plasma

Abstract

This paper is devoted to analytical and numerical studies of the parallel structure of poloidal Alfvén waves in a finite pressure plasma. The effects of finite-beta plasma are especially essential near the magnetospheric equator, where an opaque (non-transparent) region for Alfvén waves can be formed. This region is bounded by two turning points which restrain penetration of the wave energy far from the ionosphere, and an Alfvén resonator appears on a part of the field line adjacent to the ionosphere. Due to this effect the ULF pulsations in the Northern and Southern Hemispheres can be non-conjugated. Another result is a peculiar field-aligned structure of the wave magnetic field: its fundamental harmonic must have three nodes, rather than one node as is the case in cold plasma.