Post-adiabatic supernova remnants in the interstellar magnetic field. Parallel and perpendicular shocks

TL;DR

This study uses magneto-hydrodynamic simulations to explore how magnetic fields influence the evolution of radiative supernova remnants, revealing that magnetic field orientation and strength significantly affect shell density, thickness, and gamma-ray emission.

Contribution

It provides new insights into the impact of magnetic field orientation on radiative supernova remnants, highlighting the role of tangential and perpendicular fields in their evolution.

Findings

Tangential magnetic fields above 3 μG prevent dense shell formation.

Stronger tangential fields increase shell thickness and decrease maximum density.

Perpendicular magnetic fields enhance gamma-ray flux from SNRs.

Abstract

Gamma-rays from hadronic collisions are expected from supernova remnants (SNRs) located near molecular clouds. The temperature on the shock interacting with the dense environment quickly reaches $10^5$ K. The radiative losses of plasma become essential in the evolution of SNRs. They decrease the thermal pressure and essentially increase the density behind the shock. The presence of ambient magnetic field may considerably alter the behavior of the post-adiabatic SNRs comparing to hydrodynamic scenario. In the present paper, the magneto-hydrodynamic simulations of radiative shocks in magnetic field are performed. High plasma compression due to the radiative losses results also in the prominent increase of the strength of the tangential component of magnetic field behind the shock and the decrease of the parallel one. If the strength of the tangential field before the shock is higher than about $3\mathrm{\mu G}$ it prevents formation of the very dense thin shell. The higher the strength of the tangential magnetic field the larger the thickness and the lower the maximum density in the radiative shell. Parallel magnetic field does not affect the distribution of the hydrodynamic parameters behind the shock. There are almost independent channels of energy transformations: radiative losses are due to the thermal energy, the magnetic energy increases by reducing the kinetic energy. The large density and high strength of the perpendicular magnetic field in the radiative shells of SNRs should result in considerable increase of the hadronic gamma-ray flux comparing to the leptonic one.