Origin of Radially Aligned Magnetic Fields in Young Supernova Remnants

TL;DR

This study uses 3D magnetohydrodynamics simulations to investigate how the Richtmyer-Meshkov instability causes radially aligned magnetic fields in young supernova remnants, linking turbulence to observed magnetic orientations.

Contribution

It demonstrates that shock-induced turbulence preferentially amplifies radial magnetic fields, providing a physical explanation for observed radial magnetic structures in supernova remnants.

Findings

Radial bias in magnetic field amplification due to turbulence.

Richtmyer-Meshkov instability driven by shock-density interactions.

Potential observational signatures to identify upstream density fluctuation sources.

Abstract

It has been suggested by radio observations of polarized synchrotron emissions that downstream magnetic field in some young supernova remnants are oriented radially. We study magnetic field distribution of turbulent supernova remnant driven by the Richtmyer-Meshkov instability -- in other words, the effect of rippled shock -- by using three-dimensional magnetohydrodynamics simulations. We find that the induced turbulence has radially biased anisotropic velocity dispersion that leads to a selective amplification of the radial component of the magnetic field. The Richtmyer-Meshkov instability is induced by the interaction between the shock and upstream density fluctuations. Future high-resolution polarization observations can distinguish the following candidates responsible for the upstream density fluctuations: (i) inhomogeneity caused by the cascade of large-scale turbulence in the ISM so-called the big-power-law-in-the-sky, (ii) structures generated by the Drury instability in the cosmic-ray modified shock, and (iii) fluctuations induced by the non-linear feedback of the cosmic-ray streaming instability.