Microphysical Plasma Relations from Special-relativistic Turbulence

The microphysical, kinetic properties of astrophysical plasmas near accreting compact objects are still poorly understood. For instance, in modern general-relativistic magnetohydrodynamic simulations, the relation between the temperature of electrons T-e and protons T-p is prescribed in terms of simplified phenomenological models where the electron temperature is related to the proton temperature in terms of the ratio between the gas and magnetic pressures, or the beta parameter. We here present a very comprehensive campaign of two-dimensional kinetic particle-in-cell simulations of special-relativistic turbulence to investigate systematically the microphysical properties of the plasma in the transrelativistic regime. Using a realistic mass ratio between electrons and protons, we analyze how the index of the electron energy distributions kappa, the efficiency of nonthermal particle production ?, and the temperature ratio := T-e T-p vary over a wide range of values of beta and sigma. For each of these quantities, we provide two-dimensional fitting functions that describe their behavior in the relevant space of parameters, thus connecting the microphysical properties of the plasma, kappa,epsilon, and T, with the macrophysical ones beta and sigma. In this way, our results can find application in a wide range of astrophysical scenarios, including the accretion and the jet emission onto supermassive black holes, such as M87* and Sgr A*.