The dependence on collisionality of non-LTE energy conversion in decaying plasma turbulence

Energy conversion in plasmas that are not in local thermodynamic equilibrium (LTE) is a forefront research area in heliospheric turbulence. Recently, an analytical expression for the energy conversion associated with all moments of the distribution function beyond temperature was derived (Cassak et al., Phys. Rev. Lett., 130, 085201, 2023). The associated power density of energy conversion through this channel was derived and named the higher-order non-equilibrium terms (HORNET) power density (Barbhuiya et al., in prep). The physical interpretation of the HORNET power density is the rate per unit volume of energy associated with the distribution function evolving towards or away from LTE. In this study, we perform 2D particle-in-cell simulations of decaying turbulence using the VPIC code. Through a parametric study, we investigate the dependence of non-LTE energy conversion and HORNET on the plasma collisionality. We anticipate this research will provide useful information about energy conversion in weakly collisional plasmas such as the solar wind and in the collisional plasmas found in fusion devices.