A study of the transition to a turbulent shock using a coarse-graining approach to ion phase space transport

TL;DR

This paper investigates how shocks transition from laminar to turbulent states in astrophysical plasmas using hybrid-kinetic simulations and a novel coarse-graining method to analyze ion phase space transport.

Contribution

It introduces a new Eulerian coarse-graining approach to study ion transport, providing insights into shock-turbulence transition mechanisms.

Findings

Upstream proton transport behavior is key to shock transition.

The coarse-graining method yields consistent inertial range results.

Potential broader applications of the approach are discussed.

Abstract

Shocks and turbulence are ubiquitous phenomena, responsible for particle acceleration to very high energies in a large collection of astrophysical systems. Using self-consistent, hybrid-kinetic simulations with and without pre-existing turbulence, we study the transition of a shock from ``laminar'' to turbulent. We show that the changes in upstream proton transport behaviour are crucial to understand this transition, which we address quantitatively with a novel Eulerian approach. This method, based on the coarse-graining of the Vlasov equation originally introduced in one of our previous studies, gives consistent results for inertial range scales. The potential applications of the coarse-graining approach beyond the shock-turbulence system are outlined.