Ponderomotive modification of multicomponent magnetospheric plasma due to electromagnetic ion cyclotron waves

TL;DR

This paper derives a detailed expression for the ponderomotive force in multicomponent magnetospheric plasma, analyzing its effects on ion density distributions near the equator, especially considering heavy ions like helium.

Contribution

It introduces a comprehensive model for the ponderomotive force in multicomponent plasma, including heavy ions and magnetic moments, and numerically analyzes its impact on ion density in the magnetosphere.

Findings

Ponderomotive force causes ion density peaks near the equator for frequencies below helium gyrofrequency.

Heavy ions reduce the magnitude of proton density modifications caused by the ponderomotive force.

Differences are observed between dipole and dayside magnetosphere configurations.

Abstract

We derive the expression for the ponderomotive force in the real multicomponent magnetospheric plasma containing heavy ions. The ponderomotive force considered includes the induced magnetic moment of all the species and arises due to inhomogeneity of the traveling low-frequency electromagnetic wave amplitude in the nonuniform medium. The nonlinear stationary force balance equation is obtained taking into account the gravitational and centrifugal forces for the plasma consisting of the electrons, protons and heavy ions (He$^{+}$). The background geomagnetic field is taken for the dayside of the magnetosphere, where the magnetic field have magnetic "holes" (Antonova and Shabansky 1968). The balance equation is solved numerically to obtain the nonlinear density distribution of ions (H$^{+}$) in the presence of heavy ions (He$^{+}$). It is shown that for frequencies less than the helium gyrofrequency at the equator the nonlinear plasma density perturbations are peaked in the vicinity of the equator due to the action of the ponderomotive force. A comparison of the cases of the dipole and dayside magnetosphere is provided. It is obtained that the presence of heavy ions leads to decrease of the proton density modification.