Collisionless magnetic reconnection in a plasmoid chain

TL;DR

This paper uses 2D Particle-in-Cell simulations to explore the kinetic features of plasmoid chain formation and evolution during magnetic reconnection, revealing new electric field phenomena and electron dynamics.

Contribution

It uncovers two new kinetic features in plasmoid chains: intense in-plane electric fields and bipolar electric structures near the chain, advancing understanding of reconnection physics.

Findings

Discovery of intense in-plane electric fields driving ion dynamics.

Identification of bipolar electric field structures near plasmoid chains.

Observation of counter-streaming electron beams and phase space electron holes.

Abstract

The kinetic features of plasmoid chain formation and evolution are investigated by two dimensional Particle-in-Cell simulations. Magnetic reconnection is initiated in multiple X points by the tearing instability. Plasmoids form and grow in size by continuously coalescing. Each chain plasmoid exhibits a strong out-of plane core magnetic field and an out-of-plane electron current that drives the coalescing process. The disappearance of the X points in the coalescence process are due to anti-reconnection, a magnetic reconnection where the plasma inflow and outflow are reversed with respect to the original reconnection flow pattern. Anti-reconnection is characterized by the Hall magnetic field quadrupole signature. Two new kinetic features, not reported by previous studies of plasmoid chain evolution, are here revealed. First, intense electric fields develop in-plane normally to the separatrices and drive the ion dynamics in the plasmoids. Second, several bipolar electric field structures are localized in proximity of the plasmoid chain. The analysis of the electron distribution function and phase space reveals the presence of counter-streaming electron beams, unstable to the two stream instability, and phase space electron holes along the reconnection separatrices.