Nonrelativistic parallel shocks in unmagnetized and weakly magnetized plasmas

TL;DR

This study uses 2D3V particle-in-cell simulations to analyze non-relativistic shocks in unmagnetized and weakly magnetized plasmas, revealing the role of electron dynamics and magnetic fields in shock formation.

Contribution

It provides new insights into shock formation mechanisms and electron-ion behavior in non-relativistic plasma collisions relevant to supernova remnants.

Findings

Shock formation is more efficient with a large-scale magnetic field.

Electron distributions downstream are generally isotropic.

No significant pre-acceleration observed in electrons or ions.

Abstract

We present results of 2D3V particle-in-cell simulations of non-relativistic plasma collisions with absent or parallel large-scale magnetic field for parameters applicable to the conditions at young supernova remnants. We study the collision of plasma slabs of different density, leading to two different shocks and a contact discontinuity. Electron dynamics play an important role in the development of the system. While non-relativistic shocks in both unmagnetized and magnetized plasmas can be mediated by Weibel-type instabilities, the efficiency of shock-formation processes is higher when a large-scale magnetic field is present. The electron distributions downstream of the forward and reverse shocks are generally isotropic, whereas that is not always the case for the ions. We do not see any significant evidence of pre-acceleration, neither in the electron population nor in the ion distribution.