# Radiation-mediated shocks: kinetic processes and transition to collisionless shocks

## TL;DR

This paper investigates the characteristics of radiation-mediated shocks across various velocities, revealing mechanisms that can create sharp subshocks even with high radiation pressure, especially in relativistic regimes.

## Contribution

It identifies specific mechanisms causing subshock formation in radiation-mediated shocks, highlighting differences between relativistic and non-relativistic cases.

## Key findings

- High-velocity shocks can develop sharp subshocks due to specific mechanisms.
- Relativistic shocks exhibit different structures compared to non-relativistic ones.
- Implications for astrophysical shock phenomena are discussed.

## Abstract

We analyze the main features of radiation-mediated shocks at arbitrary shock velocities, both non-relativistic and relativistic. We describe two mechanisms, which may lead to formation of a sharp viscous subshock within otherwise smooth velocity profile at the shock front, even if the radiation pressure in the upstream is overwhelmingly large. These mechanisms are specific to sub-relativistic and relativistic radiation-mediated shocks and set high-velocity shocks apart from their non-relativistic counterparts, which do not develop a subshock if the radiation pressure is high enough. We briefly discuss implications of this finding.