In Situ Observations of Lower Hybrid Drift Waves at the Inner Edge of the Ring Current by the Van Allen Probe‐A

Abstract

AbstractIn the magnetosphere of the Earth, lower hybrid drift (LHD) waves effectively cause plasma diffusion and couple well to both electrons and ions. LHD waves have the characteristics of linear polarization and highly oblique propagation with frequencies near the lower hybrid resonance frequency, which is similar to the characteristics of high‐frequency magnetosonic (MS) waves. The existence of diamagnetic drift at the inner edge of the ring current provides free energy for the excitation of LHD waves, while the free energy to generate MS waves are provided by proton ring distribution. Here, we report on a typical case of LHD waves which was excited by LHD instability. Different from the global distribution of high‐frequency MS waves, statistical results indicate that most LHD waves have a uniform distribution over all MLTs except the noon sector inside the plasmapause. Besides, the occurrence of LHD waves reaches a maximum in the dusk sector outside the plasmapause.