Effects of equatorial chorus wave normal azimuthal distribution on wave propagation

Abstract

The non-ducted propagation characteristics of the VLF waves in the inner magnetosphere were studied with respect to their frequency, source localization, and initial polar angle between the wave-normal and the background magnetic field and azimuthal angle. The ray tracing software based on multi-components cold plasma approach was developed by use of the Olson-Pfitzer magnetic field model and the GCPM model of plasma density. We described dynamics of the wave-normals direction during its propagation and magnetospheric reflection. We showed that whistler waves can be reflected when lower hybrid resonance frequency becomes greater than the wave frequency: ωLH > ω. It corresponds to magnetic latitude λ ∼ 50°. The simulation results confirmed the inapplicability of the quasi-longitudinal approximation to describe the propagation of magnetospheric whistlers. The simulation results of chorus emissions propagation, which use realistic distributions of waves on the initial parameters are presented. Particularly, we obtained distributions of chorus emission waves in dependence on the wave-normal directions for different magnetic latitudes, with respect to initial azimuthal angle. It is required for studying diffusive processes in the radiation belts. The results are found to be in a good agreement with the CLUSTER STAFF-SA measurements.