PIC simulation in contact with a chaotic thermostat

A particle-in-cell (PIC) simulation in which the interacting particles are simultaneously in contact with a chaotic thermostat [G. J. Morales, Phys. Rev. E 99, 062218 (2019)] is explored. The thermostat maintains a Maxwellian velocity distribution function with a given temperature through deterministic, chaotic orbits. In the absence of a self-consistent electric field, the wave-particle interaction in this environment follows the generalized collisional plasma dispersion function [B. D. Fried, A. N. Kaufman, and D. L. Sachs, Phys. Fluids 9, 292 (1966)]. This implies that the particle response automatically evolves from the collisionless Landau limit to the Braginskii collisional behavior as the coupling time-scale to the thermostat is varied. The present work documents the ensuing collective behavior for a variety of situations, including: heating and cooling to Maxwellian distributions of prescribed temperatures, relaxation of an initial drift, response to a DC electric field, Debye-shielding of spatially periodic sources, externally-driven traveling waves, and relaxation of the two-stream instability. In addition to collective Langmuir waves, the system supports modes associated with the chaotic dynamics. These modes become more prominent as the effective collision frequency becomes comparable to the plasma frequency.