Magnetic Field Saturation of the Ion Weibel Instability in Interpenetrating Relativistic Plasmas

TL;DR

This study uses particle-in-cell simulations to analyze the saturation behavior of the ion Weibel instability in relativistic plasmas, revealing sustained magnetic fields and filament network formation.

Contribution

It demonstrates the 3D evolution of the ion Weibel instability into the Alfvén current, showing sustained magnetic energy and filament connectivity, which were not captured in previous 2D studies.

Findings

Magnetic field energy reaches 1.5% of initial beam kinetic energy.

Filaments form a connected network at saturation.

Electrons are continuously heated during filament coalescence.

Abstract

The time evolution and saturation of the Weibel instability at the ion Alfv\'en current are presented by ab initio particle-in-cell simulations. We found that the ion Weibel current in 3D could evolve into the Alfv\'en current where the magnetic field energy is sustained at 1.5\% of the initial beam kinetic energy. The current filaments are no longer isolated at saturation, but rather connected to each other to form a network structure. Electrons are continuously heated during the coalescence of the filaments, which is crucial for obtaining sustained magnetic fields with much stronger levels than with 2D simulations. The results highlight again the importance of the Weibel instability in generating magnetic fields in laboratory, astrophysical, and cosmological situations.