PIC Simulation of Electron Only Kelvin-Helmholtz Instability at the Dayside Magnetopause

The Kelvin-Helmholtz instability is one of the most important physical processes operating on the dayside magnetopause. It has been widely investigated within the MHD framework, however, the importance of kinetic effects increases when the thickness of the velocity shear layer becomes comparable to the ion gyroradius. Several observational studies indicate the existence of a thin velocity shear layer at the subsolar region with a thickness on the order of an ion gyroradius. To consider the effects of particle kinetics, we run particle-in-cell (PIC) simulations and investigate how the Kelvin-Helmholtz instability is excited along such a thin dayside magnetopause. Surprisingly, our simulations show the evolution of an electron-only Kelvin-Helmholtz vortex before the fluid scale Kelvin-Helmholtz instability occurs. While they are growing, rolled-up flows of electrons generate strong current and magnetic field increase/decrease at the center of the electron-only vortex. We will also show dramatic differences in the characteristics of electron-only vortices for different directions of shear velocity relative to the background magnetic field.