Collisionless plasma expansion in the presence of a dipole magnetic field

TL;DR

This study investigates how a high-energy plasma cloud expands in a magnetized background, forming a diamagnetic cavity and collisionless shock waves, using a hybrid kinetic-fluid model and particle-in-cell simulations.

Contribution

It provides new insights into plasma expansion dynamics in magnetic fields, combining numerical simulations with analytical models for collisionless plasma interactions.

Findings

Plasma cloud forms a diamagnetic cavity excluding magnetic fields.

Collisionless shock waves are generated during expansion.

Energy exchange aligns qualitatively with previous analytical models.

Abstract

The collisionless interaction of an expanding high-energy plasma cloud with a magnetized background plasma in the presence of a dipole magnetic field is examined in the framework of a 2D3V hybrid (kinetic ions and massless fluid electrons) model. The retardation of the plasma cloud and the dynamics of the perturbed electromagnetic fields and the background plasma are studied for high Alfven-Mach numbers using the particle-in-cell method. It is shown that the plasma cloud expands excluding the ambient magnetic field and the background plasma to form a diamagnetic cavity which is accompanied by the generation of a collisionless shock wave. The energy exchange between the plasma cloud and the background plasma is also studied and qualitative agreement with the analytical model suggested previously is obtained.