Evidence of Plasma Mixing at the Earth's Magnetopause Due To Kelvin Helmholtz Vortices

Abstract Kelvin Helmholtz Instabilities (KHI) result from interactions between the shocked solar wind and the Earth's magnetosphere. These are formed due to the velocity shear between the plasma in the magnetosphere and magnetosheath. The role of KHI in bringing in the shocked solar wind into the terrestrial magnetosphere has been studied extensively using MHD, Hall‐MHD, hybrid and PIC simulations. Such simulations oftentimes make simplifying assumptions of the boundary layer in the magnetopause. To experimentally study the effects of KHI on the boundary layer and its effectiveness in bringing in solar wind, we analyze 43 KHI events. All these events have quasi‐constant IMF orientation during its interval, thereby mitigating the effects of variation of IMF in the ongoing transient magnetopause process. In this statistical study of KHIs, we demonstrate that there is a preexisting boundary layer before KHIs begin to develop. As KHI develops to its non‐linear state, the ions in the magnetosphere, magnetopause, and magnetosheath are mixed, which is demonstrated using the alpha‐to‐proton density ratio. As a result of this mixing, the well‐defined preexisting boundary layer is replaced by a much more uniformly mixed boundary layer.