Two typical collective behaviors of the heavy ions expanding in cold plasma with ambient magnetic field

TL;DR

This study numerically investigates how the initial total mass of heavy ions influences their collective behaviors during expansion in a cold plasma with magnetic fields, revealing nonlinear effects and distinct plasma patterns.

Contribution

It demonstrates that initial mass differences can lead to entirely different collective behaviors in plasma expansion, highlighting the nonlinear nature of such phenomena.

Findings

Different initial masses induce distinct collective plasma behaviors.

Heavy ions exhibit varied stopping patterns and electron drift directions.

Nonlinear effects depend on ion densities and magnetic field variations.

Abstract

We have numerically studied the evolution of the heavy ions that expand in a cold background plasma at a large scale. Two typical collective behaviors of the heavy ions are identified with the conditions where only the traversing heavy ion's initial total mass is different. Our work has demonstrated that a difference in the initial total mass of the moving heavy ions is able to induce completely different collective behaviors of the plasma. The simulation is performed via the hybrid model, in which the ions and electrons are treated as classical particles and mass-less fluid, respectively. Due to the imbalance of the electric and magnetic force on the heavy ions, these particles will evolve into different collective patterns at the later time. These patterns manifest a rather different stopping behavior of the moving ions and an opposite drifting direction of the electron fluid at the rim of the expanding plasma. Further numerical and analytical calculations show that the imbalance depends not only on the number densities of the plasma ions, but also on the spatial variations of the magnetic fields. Our work reveals that the collective behavior of the heavy ions is highly non-linear, and the non-linearity is able to induce different phenomena in the evolution of the system at a large scale.