Effects of equatorial chorus wave normal azimuthal distribution on wave propagation

International audienceThe 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: ω_{LH}>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

Specific features of VLF wave propagation in the earth’s inner magnetosphere

International audienceThe ray trajectories of waves in the very low frequency (VLF) range in the case of nonducted propagation in the earth's inner magnetosphere are studied as functions of location of their source region, frequency, and initial angle between the vector of wave normal and intensity vector of external magnetic field. Simulation is performed on the basis of geometric ray tracing approach in multicomponent plasma. The parameters of the magnetospheric medium were calculated using a diffusion model of the concentration distribution of plasma components and the International Geomagnetic Reference Field (IGRF) model. It is shown that the magnetospheric wave reflection can occur if the lower hybrid resonance frequency is greater than its own wave frequency (omega (LHF) > omega), i.e., at the latitudes lambda a parts per thousand 50A degrees. The simulation results confirm that the quasi-longitudinal approximation cannot be used to describe the magnetospheric whistler propagation. We present simulations of propagation of chorus-type wave magnetospheric emissions that were performed using realistic wave distributions over initial parameters. In particular, we present distributions of chorus waves over directions of wave vector as functions of geomagnetic latitude; these distributions are required to study the particle scattering and acceleration processes in the radiation belts. Our results well agree with CLUSTER satellite measurements

Effects of equatorial chorus wave normal azimuthal distribution on wave propagation

International audienceThe 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: ω_{LH}>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