Magnetic shaping of SNRs and their bubbles

Abstract

We have simulated the evolution of a supernova remnant embedded in a galactic magnetic field using 2D numerical MHD. The calculation generalizes the spherically symmetric results of Slavin and Cox (1992) to 2D axisymmetric geometry. We follow the evolution of the remnant for 5×106 yr—sufficiently long for the effects of magnetic shaping and radiative cooling of the hot bubble to become important. We find that: (1) the shock wave becomes increasingly oblate and the hot bubble becomes increasingly prolate with respect to the magnetic axis with time; (2) the radiative shell remains thick except at the magnetic poles due to magnetic pressure support; (3) near the magnetic poles a dense polar cap of HI forms at the bubble apex; (4) a complex shock system including a shock ‘‘dimple’’ forms near the magnetic axis when the shock speed has dropped to slightly greater than the ambient Alfven speed; (5) after 5 Myr the hot bubble collapses to a slender, 400 pc‐long cylinder with T≊107 K.