Multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized reacting plasma

TL;DR

This study presents the first self-consistent multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized plasma, revealing fast reconnection rates and secondary instabilities relevant to solar phenomena.

Contribution

It introduces a novel multi-fluid simulation model including ion-neutral interactions, ionization, and recombination, demonstrating their impact on reconnection dynamics in the chromosphere.

Findings

Reconnection rate becomes fast and independent of Lundquist number due to ion recombination.

Decoupling of neutral and ion fluids occurs upstream, creating ionization imbalance.

Secondary tearing instability occurs at lower Lundquist numbers than in fully ionized plasmas.

Abstract

We present results from the first self-consistent multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized reacting plasma. We simulate two dimensional magnetic reconnection in a Harris current sheet with a numerical model which includes ion-neutral scattering collisions, ionization, recombination, optically thin radiative loss, collisional heating, and thermal conduction. In the resulting tearing mode reconnection the neutral and ion fluids become decoupled upstream from the reconnection site, creating an excess of ions in the reconnection region and therefore an ionization imbalance. Ion recombination in the reconnection region, combined with Alfv\'{e}nic outflows, quickly removes ions from the reconnection site, leading to a fast reconnection rate independent of Lundquist number. In addition to allowing fast reconnection, we find that these non-equilibria partial ionization effects lead to the onset of the nonlinear secondary tearing instability at lower values of the Lundquist number than has been found in fully ionized plasmas.These simulations provide evidence that magnetic reconnection in the chromosphere could be responsible for jet-like transient phenomena such as spicules and chromospheric jets.