Effective Collision Operator for Heat-Flux-Generated Whistler Turbulence

High-beta plasmas can be highly magnetized at the largest astrophysical scales, e.g., in the intracluster medium (ICM) of galaxy clusters. If the plasma is furthermore weakly collisional, the transport of momentum and heat is highly anisotropic with respect to the magnetic field direction. In thermally stratified plasmas at sufficiently high beta, the parallel heat flux can be large enough to trigger a kinetic whistler instability, which back-reacts on the transport by deforming the field lines on electron-Larmor scales. In this work, we use the particle-in-cell code Tristan-MP to calculate the steady-state heat flux through a stratified, high-beta, collisionless, magnetized plasma. By tracking a quarter million particles and simulating across a range of beta and temperature gradient length scales, we calculate the effective collision operator for heat-flux-driven whistler turbulence and use it to solve the Chapman-Enskog-Braginskii problem. We compare the resulting transport equations with existing models and discuss their implications for magneto-thermal convection and the structure of the ICM.