Cold Plasma Heating by Lower Hybrid Waves Excited by Warm Proton Ring Distribution in the Inner Magnetosphere

Abstract

In the Earth's magnetosphere, lower hybrid (LH) waves are frequently observed due to their low excitation threshold. These waves exhibit efficient coupling with electrons and ions, leading to electron heating parallel to the background magnetic field and ion heating in the perpendicular direction. Simulation results suggest that LH waves can be locally excited by a proton ring distribution. However, it is important to note that, as of now, direct satellite observations confirming this excitation mechanism have not been reported in the inner magnetosphere. In this study, we investigate a representative case of LH wave generation triggered by a warm proton ring distribution. During this event, observations combined with simulations also reveal the significant enhancements in perpendicular cold proton fluxes.