Toward a Realistic Evaluation of Transport Coefficients in Non-equilibrium Space Plasmas

Abstract

Recent studies have outlined the interest for the evaluation of transport coefficients in space plasmas, where the observed velocity distributions of plasma particles are conditioned not only by the binary collisions, e.g., at low energies, but also by the energization of particles from their interaction with wave turbulence and fluctuations, generating the suprathermal kappa-distributed populations. This paper provides a first estimate of the main transport coefficients based on regularized kappa distributions, which, unlike standard kappa distributions (SKDs), enable macroscopic parameterization without mathematical divergences or physical inconsistencies. All transport coefficients derived here, i.e., the diffusion and mobility coefficients, electric conductivity, thermoelectric coefficient, and thermal conductivity, are finite and well defined for all values of kappa > 0. Moreover, for low values of kappa (i.e., below the SKD poles), the transport coefficients can be orders of magnitudes higher than the corresponding Maxwellian limits, meaning that significant underestimations can be made if suprathermal electrons are ignored.