PIC simulations of the Thermal Anisotropy-Driven Weibel Instability: Field growth and phase space evolution upon saturation

TL;DR

This paper uses PIC simulations to study the growth and saturation of the thermal anisotropy-driven Weibel instability in an electron plasma, revealing details of field evolution and electron phase space redistribution.

Contribution

It provides new insights into the field growth, phase space evolution, and the role of electrostatic and magnetic fields during the saturation of the Weibel instability.

Findings

Electric and magnetic fields redistribute electrons upon saturation.

Electrostatic fields are driven by magnetic pressure gradients.

Wave spectrum initially confined to one dimension in 2D simulations.

Abstract

The Weibel instability is investigated with PIC simulations of an initially unmagnetized and spatially uniform electron plasma. This instability, which is driven by the thermally anisotropic electron distribution, generates electromagnetic waves with wave vectors perpendicular to the direction of the higher temperature. Two simulations are performed: A 2D simulation, with a simulation plane that includes the direction of higher temperature, demonstrates that the wave spectrum is initially confined to one dimension. The electric field components in the simulation plane generated by the instability equalize at the end of the simulation through a secondary instability. A 1D PIC simulation with a high resolution, where the simulation box is aligned with the wave vectors of the growing waves, reveals details of the electron phase space distribution and permits a comparison of the magnetic and electric fields when the instability saturates. It is shown that the electrostatic field is driven by the magnetic pressure gradient and that it and the magnetic field redistribute the electrons in space.