Coulomb collision rates for self-similar and kappa distributions

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Abstract
The Coulomb collision operator for two nonthermal particle distributions, the self‐similar and kappa distribution, is investigated theoretically. Associated friction and diffusion rates are evaluated and calculated numerically as a function of velocity. It is shown that the full collision term can be cast into a relaxation time form with an effective collision rate that differs drastically from the smooth overall diffusion rates and is very sensitive to the shape of the distribution. Numerical results for the effective rates are presented and the relevance of our analysis with respect to observed distributions in space plasmas and for quasilinear turbulence is discussed.