Electromagnetic field generation in the downstream of electrostatic shocks due to electron trapping

TL;DR

This paper discovers a new magnetic field generation mechanism in electrostatic shocks caused by electron trapping, leading to significant magnetic fields that influence downstream particle trajectories without altering shock formation.

Contribution

It introduces a novel magnetic field generation process in electrostatic shocks driven by electron trapping and temperature anisotropy, which was not previously understood.

Findings

Magnetic energy density can reach 0.01 of kinetic energy density.

Generated magnetic fields are confined to the downstream region.

Shock formation and ion acceleration features remain unchanged.

Abstract

A new magnetic field generation mechanism in electrostatic shocks is found, which can produce fields with magnetic energy density as high as 0.01 of the kinetic energy density of the flows on time scales $ \tilde \, 10^4 \, {\omega}_{pe}^{-1}$. Electron trapping during the shock formation process creates a strong temperature anisotropy in the distribution function, giving rise to the pure Weibel instability. The generated magnetic field is well-confined to the downstream region of the electrostatic shock. The shock formation process is not modified and the features of the shock front responsible for ion acceleration, which are currently probed in laser-plasma laboratory experiments, are maintained. However, such a strong magnetic field determines the particle trajectories downstream and has the potential to modify the signatures of the collisionless shock.