Fully Kinetic Simulations of Plasma Transport and Particle Energization Induced by the Kelvin-Helmholtz Instability at the Earth’s Magnetopause

The Kelvin-Helmholtz instability (KHI) at the Earth's magnetospheric flanks plays a critical role in driving plasma dynamics, particularly during northward interplanetary magnetic field periods, in which the KHI is active at the low latitude magnetopause. This instability arises due to the velocity shear between solar wind and magnetospheric plasma, forming vortex structures that drive plasma mixing and magnetic reconnection. These vortices generate turbulence and enable the transfer of energy, momentum, and particles across the magnetopause. As a result, the KHI significantly impacts processes like plasma transport and particle acceleration in planetary magnetospheres. 

To investigate the small-scale physics of these processes, we performed high-resolution two-dimensional (2D) fully kinetic particle-in-cell (PIC) simulations using the ECsim code. ECsim stands out as a PIC code that has the unique property of conserving energy to machine precision, which is essential for accurately modeling physical systems where energy transfer is of prime importance. Our simulations focus on conditions characteristic of the Earth's magnetospheric flanks, where the KHI develops and evolves. By examining different plasma parameters, concentrating on particle velocity distribution functions and temperature anisotropies, we analyze the microphysical processes driving plasma mixing and particle energization, with a particular focus on electron physics, which is captured here in full.