CosmoMHD: A Cosmological Magnetohydrodynamics Code

In this era of precision cosmology, a detailed physical understanding on the evolution of cosmic baryons is required. Cosmic magnetic fields, though still poorly understood, may represent an important component in the global cosmic energy flow that affects the baryon dynamics. We have developed an Eulerianbased cosmological magnetohydrodynamics code (CosmoMHD) with modern shock capturing schemes to study the formation and evolution of cosmic structures in the presence of magnetic fields. The code solves the ideal MHD equations as well as the non-equilibrium rate equations for multiple species, the Vlasov equation for dynamics of collisionless particles, the Poisson’s equation for the gravitational potential field and the equation for the evolution of the intergalactic ionizing radiation field. In addition, a detailed star formation prescription and feedback processes are implemented. Several methods for solving the MHD by high-resolution schemes with finite-volume and finite-difference methods are implemented. The divergence-free condition of the magnetic fields is preserved at a level of computer roundoff error via the constraint transport method. We have also implemented a high-resolution method via dual-equation formulations to track the thermal energy accurately in very high Mach number or high AlfvenMach number regions. Several numerical tests have demonstrated the efficacy of the proposed schemes. Subject headings: cosmology: theory — magnetohydrodynamics — methods: numerical — shock waves