Alfvén Waves at the Interface of Solar Wind and Magnetosphere

At Earth's magnetopause, kinetic Alfvén waves play a crucial role in energy transport via mode conversion from compressional waves and mode coupling with Kelvin-Helmholtz (KH) waves. When the wave frequency is close to the ion cyclotron frequency, the compressional wave energy can transfer to the perpendicular ion cyclotron resonance (PICR), and this mode conversion effectively occurs at the magnetopause. We show that the mode-converted kinetic Alfvén waves at the PICR location radiate toward the magnetosheath, where the wave frequency ( ω ) is higher than the local PICR frequency ( ω PICR ). In the KH vortex, the PICR frequency can oscillate in the radial direction; therefore, these waves can be trapped in the KH vortex in regions where ω > ω PICR . When the shear flow ( V 0 ) in the magnetosheath is considered, for low Alfvén Mach number, secondary KH waves having a lower frequency than the primary KH become unstable at the interface. When the shear flow transition layer exists between the magnetosheath and the magnetosphere, strong coupling between the shear Alfvén waves and the secondary KH wave occurs. As a result, significant wave energy can transfer from the boundary layer to the inner magnetosphere.