MHD supernova explosions -- Large-scale magnetic field effects

We examine the effect of uniform ambient magnetic fields on the evolution of supernova-driven blast waves into a homogeneous ambient ISM in thermal equilibrium. Using the Pencil Code we simulate high resolution nonideal magnetohydrodynamic simulations in 3D. We find that supernova blast waves are sensitive to plane-parallel magnetic fields of strength in excess of 1 $\mu$G for ambient gas number density 1 cm$^{-3}$ . Perpendicular to the field, the inward magnetic pressure gradient induces retrograde mass accretion in the wake of the primary shock front. Subsequently, we find that the primary shockwave expands faster perpendicular to the field, but with reduced momentum, while the remnant core is subject to magnetic confinement. This leads to a decrease in fractional volume of hot gas but also an increase in the density and temperature of hot gas in the magnetically confined remnant. The magnetic pressure gradient behind the shock front generates enhanced regions favourable to UV- heating and thus reduces net radiative losses. Although the presence of a strong uniform magnetic field can reduce momentum early on, and hence residual kinetic energy, it increases the efficiency of residual total energy injection by the SN into the ISM by up to 40% within 1 Myr.