A Study of the Early-stage Evolution of Relativistic Electron-Ion Shock using 3D PIC Simulations

TL;DR

This study uses 3D PIC simulations to analyze the early evolution of relativistic electron-ion shocks, revealing complex shock structures, particle behaviors, and magnetic energy growth in unmagnetized jet interactions.

Contribution

First detailed 3D simulation of early-stage relativistic electron-ion shock evolution showing hybrid shock structures and particle dynamics.

Findings

Hybrid shock structures observed with electrostatic and double layer features

Ambient ions show penetration and acceleration across shocks

Magnetic energy density reaches a few percent of jet kinetic energy

Abstract

We report the results of a 3D particle-in-cell (PIC) simulation carried out to study the early-stage evolution of the shock formed when an unmagnetized relativistic jet interacts with an ambient electron-ion plasma. Full-shock structures associated with the interaction are observed in the ambient frame. When open boundaries are employed in the direction of the jet; the forward shock is seen as a hybrid structure consisting of an electrostatic shock combined with a double layer, while the reverse shock is seen as a double layer. The ambient ions show two distinct features across the forward shock: a population penetrating into the shocked region from the precursor region and an accelerated population escaping from the shocked region into the precursor region. This behavior is a signature of a combination of an electrostatic shock and a double layer. Jet electrons are seen to be electrostatically trapped between the forward and reverse shock structures showing a ring-like distribution in a phase-space plot, while ambient electrons are thermalized and become essentially isotropic in the shocked region. The magnetic energy density grows to a few percent of the jet kinetic energy density at both the forward and the reverse shock transition layers in a rather short time scale. We see little disturbance of the jet ions over this time scale.