Weibel instability and associated strong fields in a fully 3D simulation of a relativistic shock

TL;DR

This paper uses a new 3D relativistic particle-in-cell simulation to study the nonlinear development of Weibel instability, particle acceleration, and shock formation in unmagnetized relativistic electron-positron jets, relevant to astrophysical phenomena.

Contribution

It presents the first long-duration 3D simulation of relativistic shocks showing detailed shock structure, particle thermalization, and electromagnetic field generation in unmagnetized plasmas.

Findings

Electron density increases by a factor of 3.5 at the shock

Strong electromagnetic fields are generated in the trailing shock

Partial hydrodynamic shock structure is formed

Abstract

Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) excited in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a new 3-D relativistic particle-in-cell code, we have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. The simulation has been performed using a long simulation system in order to study the nonlinear stages of the Weibel instability, the particle acceleration mechanism, and the shock structure. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic (HD) like shock structure. In the leading shock, electron density increases by a factor of 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. We discuss the possible implication of our simulation results within the AGN and GRB context.