Mode Coupling From Kinetic Alfvén Waves to Electron Acoustic Waves in the Topside Ionosphere

Abstract

AbstractThe propagation and energy transfer of kinetic Alfvén waves (KAWs) in the topside ionosphere are investigated based on a drift kinetic model. We examine the dependence of the generation of electron acoustic waves (EAWs) on the perpendicular wavelength and on the hot electron temperature. With decreasing perpendicular wavelength and increasing hot electron temperature, the coupling of KAWs to EAWs becomes increasingly important. The Landau damping of the EAWs is strong except in the transition region, where the nonlinear dissipation can be important. With increasing wave amplitude, the generated electron acoustic mode waves become unsustainable when the depletion of cold electron density is comparable to the initial background cold electron density. These findings indicate that electron acoustic mode waves play an important role at kinetic scales in the topside ionosphere.