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 Eulerian-based cosmological magnetohydrodynamics code (CosmoMHD) with modern shock capturing schemes to study the formation and evolution of cosmic structures in the presence of magnetic fields. We have implemented several high-resolution finite-volume and finite-difference methods for solving the MHD equations with cosmology. The divergence-free condition of the magnetic fields is preserved at a level of computer round-off error via the constraint transport method. We have also implemented a high-resolution method via dual-equation formulation to track the thermal energy of the baryons accurately in very high Mach number or high Alfven-Mach number regions. Several numerical tests have demonstrated the efficacy of the proposed schemes.