Simulating the effects of ion mass-to-charge ratios on the Kelvin-Helmholtz instability *

The Kelvin-Helmholtz instability can occur in many different astrophysical plasma environments, such as at the Earth's magnetosphere, the accretion disks and jets of active galactic nuclei, and pulsars. These environments have ion-to-electron mass ratios that range from much less than unity in dusty plasma, to unity in relativistic electron-positron jets, to 1836 in ionospheric plasmas, to 10^4 and beyond in experimental heavy ion plasmas. We want to understand how the presence of ions affects the dynamics of the Kelvin-Helmholtz instability through a careful analytical treatment and with two-dimensional ZPIC particle-in-cell simulations. We vary the charge-to-mass ratio of the superimposed ions to determine how this affects the growth rate, particle acceleration, and magnetic and electric field generation of the instability. This is done by extracting the phase space distribution in both spatial dimensions as well as both the magnetic and electric field in real space from fully kinetic simulations.