Mathematical Modeling of Kelvin–Helmholtz Instability at Tangential Discontinuities in Partially Ionized Plasma: Application to Heliopause Dynamics

The stability of the heliopause, the tangential discontinuity separating the solar wind from the interstellar medium, is influenced by various processes, including the Kelvin–Helmholtz instability. This study investigates the role of charge exchange collisions between protons and hydrogen (H) atoms in reduction of the Kelvin–Helmholtz growth rate at the heliopause. Using a two-dimensional gasdynamic model with the inclusion of H atoms, we perform numerical simulations of the plasma flow near the heliopause flanks. We conduct a parametric study by varying the Knudsen number. Our results indicate that charge exchange collisions play a crucial role in suppressing the Kelvin–Helmholtz instability. As the Knudsen number decreases, the flow transitions from an unstable regime to a smoother state.