On a Propagation of Gendrin-Mode Waves in the Magnetosphere

Abstract

This paper presents results from the analytical and numerical investigations of the propagation of Gendrin-mode whistler waves in the magnetosphere. These waves are important for the interpretation of satellite observations and planning experiments in laboratory and space plasma because the perpendicular component of their group velocity is equal to zero, and hence, they can supposedly propagate over a significant distance along an ambient magnetic field without attenuation. Simulations of the electron MHD equations demonstrate that these waves generated by the source with a finite transverse size experience a substantial diffraction, leading to the diminishing of wave amplitude with distance from the source. The effect of the diffraction is inversely proportional to the transverse size of the wave packet. Simulations also reveal that these waves can be trapped and guided along the ambient magnetic field by the field-aligned irregularities (aka ducts) in the plasma density or the magnetic field. Specifically, the Gendrin-mode waves can be efficiently trapped by the low-density or high-magnetic ducts with a very small (1%) difference in magnitudes of the parameters inside and outside the ducts. High-density and low-magnetic ducts do not trap these waves.