# Magnetic stochasticity and diffusion

## TL;DR

This paper establishes a quantitative link between magnetic stochasticity and diffusion in turbulent magnetized media, supported by MHD simulations, highlighting the role of stochastic magnetic reconnection in accelerating magnetic reconnection processes.

## Contribution

It introduces a mathematical formulation of magnetic stochasticity based on ${
m L}_p$-norms and demonstrates its connection to magnetic diffusion through MHD simulations, advancing understanding of turbulence effects.

## Key findings

- Magnetic diffusion follows super-linear Richardson dispersion in turbulence.
- Stochastic magnetic reconnection accelerates reconnection by broadening outflow.
- Simulation results confirm the theoretical relationship between stochasticity and diffusion.

## Abstract

We develop a quantitative relationship between magnetic diffusion and the level of randomness, or stochasticity, of the diffusing magnetic field in a magnetized medium. A general mathematical formulation of magnetic stochasticity in turbulence has been developed in previous work in terms of the ${\cal L}_p$-norm $S_p(t)={1\over 2}|| 1-\hat{\bf B}_l.\hat{\bf B}_L||_p$, $p$th order magnetic stochasticity of the stochastic field ${\bf B}({\bf x}, t)$, based on the coarse-grained fields, ${\bf B}_l$ and ${\bf B}_L$, at different scales, $l\neq L$. For laminar flows, stochasticity level becomes the level of field self-entanglement or spatial complexity. In this paper, we establish a connection between magnetic stochasticity $S_p(t)$ and magnetic diffusion in magnetohydrodynamic (MHD) turbulence and use a homogeneous, incompressible MHD simulation to test this prediction. Our results agree with the well-known fact that magnetic diffusion in turbulent media follows the super-linear Richardson dispersion scheme. This is intimately related to stochastic magnetic reconnection in which super-linear Richardson diffusion broadens the matter outflow width and accelerates the reconnection process.