Kinetic Simulations of Plasmoid Chain Dynamics

TL;DR

This study uses 3D Particle-in-Cell simulations to explore how plasmoid chains form and evolve during magnetic reconnection, revealing the influence of guide fields on their structure and dynamics.

Contribution

It provides new insights into the role of guide fields in plasmoid chain evolution and the formation of electron holes during magnetic reconnection.

Findings

Guide field affects plasmoid size and hierarchy.

Without guide field, hierarchical plasmoid structures form.

Presence of guide field leads to electron hole formation.

Abstract

The dynamics of a plasmoid chain is studied with three dimensional Particle-in-Cell simulations. The evolution of the system with and without a uniform guide field, whose strength is 1/3 the asymptotic magnetic field, is investigated. The plasmoid chain forms by spontaneous magnetic reconnection: the tearing instability rapidly disrupts the initial current sheet generating several small-scale plasmoids, that rapidly grow in size coalescing and kinking. The plasmoid kink is mainly driven by the coalescence process. It is found that the presence of guide field strongly influences the evolution of the plasmoid chain. Without a guide field, a main reconnection site dominates and smaller reconnection regions are included in larger ones, leading to an hierarchical structure of the plasmoid-dominated current sheet. On the contrary in presence of a guide field, plasmoids have approximately the same size and the hierarchical structure does not emerge, a strong core magnetic field develops in the center of the plasmoid in the direction of the existing guide field, and bump-on-tail instability, leading to the formation of electron holes, is detected in proximity of the plasmoids.