A finite volume method for two-moment cosmic ray hydrodynamics on a moving mesh

ABSTRACT We present a new numerical algorithm to solve the recently derived equations of two-moment cosmic ray hydrodynamics (CRHD). The is implemented as module in moving mesh Arepo code. Therein, anisotropic transport rays (CRs) along magnetic field lines discretized using path-conservative finite volume method on unstructured time-dependent Voronoi Arepo. interaction CRs and gyroresonant Alfvén waves described by short time-scale source terms CRHD equations. employ custom-made semi-implicit adaptive time stepping term integrator accurately integrate this small light-crossing step. Both integration step are separated from evolution magnetohydrodynamical an operator split approach. tested with variety test problems, including shock tubes, perpendicular magnetized discontinuity, hydrodynamic response CR overpressure, acceleration warm cloud, blast wave, which demonstrate that coupling between magnetohydrodynamics robust accurate. convergence presented scheme linear non-linear analytic solutions.