Collisionless Magnetic Reconnection in a Five-Moment Two-Fluid Electron-Positron Plasma

TL;DR

This study investigates magnetic reconnection in collisionless electron-positron plasma using a two-fluid model, finding that fast reconnection requires numerical diffusion in the absence of Hall effects or pressure anisotropy.

Contribution

It demonstrates that isotropic pressure in pair plasma does not lead to fast reconnection without numerical diffusion, contrasting with previous models with Hall effects or pressure anisotropy.

Findings

Fast reconnection in pair plasma requires numerical diffusion.

Hall effects or pressure anisotropy facilitate fast reconnection.

Isotropic pressure alone does not produce fast reconnection.

Abstract

We simulate magnetic reconnection in electron-positron (pair) plasma using a collisionless two-fluid model with isotropic pressure. In this model the resistive, Hall, and electrokinetic pressure terms are absent from the curl of Ohm's law, leaving the inertial term alone to provide for magnetic reconnection. Our simulations suggest that for pair plasma simulated with isotropic pressure fast reconnection does not occur without the aid of sufficient (numerical) diffusion. We contrast this result with simulations and published results showing fast reconnection for collisionless two-fluid plasma with isotropic pressures and non-canceling mass-to-charge ratios, where Hall effects are present and numerical diffusion is small, and with published PIC studies of pair plasma which observe fast reconnection and attribute it to nonisotropic pressure.