Perpendicular diffusion of energetic particles in noisy reduced magnetohydrodynamic turbulence

TL;DR

This paper investigates how energetic particles diffuse across magnetic fields in noisy reduced magnetohydrodynamic turbulence, comparing analytical theories with simulations, and finds UNLT theory accurately predicts diffusion.

Contribution

It evaluates and compares NLGC and UNLT theories for perpendicular diffusion, confirming UNLT's accuracy through simulations in a specific turbulence model.

Findings

UNLT theory accurately predicts perpendicular diffusion.

NLGC theory provides different, less accurate results.

Simulations confirm UNLT's effectiveness in this context.

Abstract

Recently a model for noisy reduced magnetohydrodynamic turbulence was proposed. The latter model was already used to study the random walk of magnetic field lines. In the current article we use the same model to investigate the diffusion of energetic particles across the mean magnetic field. To compute the perpendicular diffusion coefficient two analytical theories are used, namely the Non- Linear Guiding Center (NLGC) theory and the Unified Non-Linear Transport (UNLT) theory. It is shown that the two theories provide different results for the perpendicular diffusion coefficient. We also perform test-particle simulations for the aforementioned turbulence model. We show that only the UNLT theory describes perpendicular transport accurately confirming that the latter theory is a powerful tool in diffusion theory.