On the Polarization of Half-Gyrofrequency Whistler-Mode Waves in the Two-Component Magnetospheric Plasma

Abstract

Quasi-electrostatic half-gyrofrequency whistler-mode VLF emissions with wave normals close to the oblique resonance cone (θ_res) have been found to be unstable for the two-component (cold and anisotropic lower-energy hot electrons) magnetospheric plasma. The present paper deals theoretically with the electric field polarization of half-gyrofrequency whistler-mode waves in such an unstable plasma, by means of numerically solving the full dispersion relation. At wave normal angles relatively away from θ_res, there exists no effect of hot electrons on the polarization. When the wave normal angle further increases above a specific value (smaller by 5–10° from θ_res) where we have wave growth, we expect the deformation of electric field polarization from that predicted by cold plasma theory; the wave becomes more transverse. The deformation becomes more pronounced for more populated hot electrons with fixed cold plasma density.