Kinetic Turbulence in Pressure-Anisotropic, High-Beta Plasmas*

Many space and astrophysical plasmas, such as the solar wind, low-luminosity black-hole accretion flows, and the intracluster medium, are hot and dilute, which makes them weakly collisional or collisionless, with plasma beta of order unity or larger. Kinetic processes, occurring on scales much smaller than what could realistically be observed from Earth, can dramatically influence the emission from these systems by shaping particles' distribution functions through the dissipation of the cascade and by introducing magnetic-field-biased deviations from local thermodynamic equilibrium, which could make the plasma unstable to a number of kinetic microinstabilities. These instabilities introduce an effective collisionality into otherwise collisionless plasma and impact the dynamics of turbulent fluctuations. In this talk, the results from hybrid-kinetic simulations are used to explore the interplay between kinetic micro-instabilities and the turbulent cascade. In particular, we obtain the effective collisionality and viscous scale in collisionless high-beta turbulence, quantify the non-local energy transfer mediated by the micro-instabilities, and determine the partition of energy between particle species.