Ion Channel Dynamics in Temperature-Dependent Weibel Instability Saturation

TL;DR

This study uses continuum Vlasov-Maxwell simulations to analyze ion channel dynamics during temperature-dependent Weibel instability saturation, revealing key differences in electron and ion thermalization in plasma shocks.

Contribution

It provides new insights into ion channel merging and magnetic structure evolution during the late stages of the ion-Weibel instability in collisionless plasmas.

Findings

Magnetic energy increases as ion channels merge.

Electrons reach thermal equilibrium rapidly, ions thermalize slowly.

Simulation results align with astrophysical and space observations.

Abstract

We present 1X2V continuum Vlasov-Maxwell simulations of interpenetrating plasma beams with mobile ions. While the early-time evolution is similar to the stationary-ion case, the late-time dynamics are dominated by the ion-Weibel instability. As ion channels merge, the magnetic energy increases and the magnetic structures extend further along the beam direction. Electrons rapidly reach thermal equilibrium, whereas ions retain distinct bulk velocities for much longer and thermalize more slowly. These results are relevant to collisionless shock formation in astrophysical compact objects and laser-plasma experiments. Wind/SWE observations place all four simulated cases in the firehose/Weibel-unstable region of the proton temperature anisotropy diagram, and MMS1 observations of a quasi-perpendicular bow shock ($\theta_{Bn}\approx83^\circ$, $M_A\approx27$) show a qualitatively similar electron-ion thermalization disparity.