Turbulent magnetic reconnection in 2D and 3D

TL;DR

This paper provides numerical evidence that magnetic reconnection in 3D turbulent fluids occurs rapidly, independent of resistivity, with significant implications for astrophysical phenomena, while 2D reconnection remains resistivity-dependent and slow.

Contribution

The study demonstrates through 3D simulations that turbulent magnetic reconnection occurs rapidly and is resistivity-independent, supporting the stochastic diffusion model.

Findings

Reconnection speed in 3D turbulence is comparable to turbulence rms velocity.

Reconnection in 3D turbulence is resistivity-independent and fast.

Reconnection in 2D turbulence remains slow and resistivity-dependent.

Abstract

Magnetic field embedded in a perfectly conducting fluid preserves its topology for all time. Although ionized astrophysical objects, like stars and galactic disks, are almost perfectly conducting, they show indications of changes in topology, `magnetic reconnection', on dynamical time scales. Reconnection can be observed directly in the solar corona, but can also be inferred from the existence of large scale dynamo activity inside stellar interiors. Solar flares and gamma ray busts are usually associated with magnetic reconnection. Previous work has concentrated on showing how reconnection can be rapid in plasmas with very small collision rates. Here we present numerical evidence, based on three dimensional simulations, that reconnection in a turbulent fluid occurs at a speed comparable to the rms velocity of the turbulence, regardless of the value of the resistivity. In particular, this is true for turbulent pressures much weaker than the magnetic field pressure so that the magnetic field lines are only slightly bent by the turbulence. These results are consistent with the proposal by Lazarian and Vishniac (1999) that reconnection is controlled by the stochastic diffusion of magnetic field lines, which produces a broad outflow of plasma from the reconnection zone. This work implies that reconnection in a turbulent fluid typically takes place in approximately a single eddy turnover time, with broad implications for dynamo activity and particle acceleration throughout the universe. In contrast, the reconnection in 2D configurations in the presence of turbulence depends on resistivity, i.e. is slow.