Universal power-law distribution functions in an electromagnetic kinetic plasma: implications for the inverted temperature profile in the solar corona

Abstract

We develop a self-consistent quasilinear theory for the relaxation of electromagnetic kinetic plasmas, and demonstrate that the mean distribution functions of both electrons and ions tend to relax to a universal $v^{-5}$ tail. Large-scale electromagnetic (EM) fields efficiently accelerate the unscreened, fast particles but not the screened, slow ones. This non-thermal tail may arise in the solar corona from EM turbulence despite collisions, allowing suprathermal particles to escape the sun's gravity (velocity filtration) and inverting the temperature $(T)$ profile with $T$ rising to $10^6$ K.