Princeton University Astroplasmas Seminar

Cosmic ray (CR) feedback significantly influences galaxy evolution by shaping the dynamics of interstellar and intergalactic media. To comprehend the microphysics underlying CR feedback, kinetic numerical simulations are imperative. I employ magnetohydrodynamic particle-in-cell (MHD-PIC) simulations are to explore the saturation of the CR pressure anisotropy instability. This instability arises from background expansion/compression and is counterbalanced by ion-neutral damping. I quantify the effective scattering rate and CR anisotropy level at saturation, scaling with environmental parameters. These findings hold promise for potential implementation as subgrid physics in CR hydrodynamics. Nonetheless, several enigmatic aspects of CR feedback in microphysics remain unresolved. Towards the conclusion of this discourse, potential avenues for kinetic simulations exploring the CR streaming bottleneck and resonant curvature will be deliberated.