Wave-particle interaction in contact with a chaotic thermostat

This study explores the properties of the wave-particle interaction when the particle is in contact with an environment that causes the velocity distribution function to be a Maxwellian. The mathematical construct used to describe such an environment is referred to as a ‘chaotic thermostat’ [G. J. Morales, Phys. Rev. E 99, 062218 (2019)] because the zero-order particle orbits belong to the category of deterministic chaos. It is found that in the limit of weak coupling to the thermostat the behavior is that predicted by the plasma dispersion function, which implies collisionless Landau damping. As the coupling to the thermostat is increased (equivalent to increasing collisionality) the behavior follows the generalized collisional plasma dispersion function [B. D. Fried, A. N. Kaufman, and D. L. Sachs, Phys. Fluids 9, 292 (1966)]. For strong coupling the response agrees with the Braginskii mobility. The nonlinear mobility associated with intermittent particle trapping is obtained for the various collisional regimes.