Onset of Fast Magnetic Reconnection in Partially Ionized Gases

TL;DR

This paper investigates how partial ionization in plasmas affects the onset of fast magnetic reconnection, showing that significant ion-neutral collisions lower the threshold for rapid reconnection, relevant in astrophysical environments.

Contribution

It demonstrates that ion-neutral collisions in partially ionized plasmas enable faster magnetic reconnection at lower Lundquist numbers than in fully ionized plasmas.

Findings

Fast reconnection occurs at lower Lundquist numbers in partially ionized plasmas.

Conditions for fast reconnection are met in molecular clouds and protostellar disks.

Ion-neutral collisions significantly influence magnetic reconnection dynamics.

Abstract

We consider quasi-stationary two-dimensional magnetic reconnection in a partially ionized incompressible plasma. We find that when the plasma is weakly ionized and the collisions between the ions and the neutral particles are significant, the transition to fast collisionless reconnection due to the Hall effect in the generalized Ohm's law is expected to occur at much lower values of the Lundquist number, as compared to a fully ionized plasma case. We estimate that these conditions for fast reconnection are satisfied in molecular clouds and in protostellar disks.