MHD supernova explosions -- Large-scale magnetic field effects

TL;DR

This study investigates how uniform magnetic fields influence supernova remnant evolution, revealing that magnetic fields alter shock expansion, confinement, and energy retention, thereby affecting the supernova's impact on the interstellar medium.

Contribution

It provides high-resolution 3D MHD simulations demonstrating the effects of magnetic fields on supernova remnants, a novel insight into magnetic influence on supernova feedback.

Findings

Magnetic fields >1 μG affect shock expansion and remnant morphology.

Magnetic confinement increases hot gas density and temperature.

Magnetic fields enhance energy injection efficiency into the ISM by up to 40%.

Abstract

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.