The implicit contribution of slab modes to the perpendicular diffusion coefficient of particles interacting with two-component turbulence

TL;DR

This paper investigates how slab modes indirectly influence the perpendicular diffusion of energetic particles in two-component turbulence, revealing a reduction in diffusion coefficient that aligns simulations with theory and impacts shock acceleration studies.

Contribution

It uncovers the implicit contribution of slab modes to perpendicular diffusion, which was previously overlooked, and demonstrates its effect on particle transport modeling.

Findings

Slab modes indirectly reduce the perpendicular diffusion coefficient.

The results improve agreement between simulations and analytical models.

Findings are relevant for diffusive shock acceleration mechanisms.

Abstract

We explore the transport of energetic particles in two-component turbulence in which the stochastic magnetic field is assumed to be a superposition of slab and two-dimensional modes. It is known that in magnetostatic slab turbulence, the motion of particles across the mean magnetic field is subdiffusive. If a two-dimensional component is added, diffusion is recovered. It was also shown before that in two-component turbulence, the slab modes do not explicitly contribute to the perpendicular diffusion coefficient. In the current paper the implicit contribution of slab modes is explored and it is shown that this contribution leads to a reduction of the perpendicular diffusion coefficient. This effect improves the agreement between simulations and analytical theory. Furthermore, the obtained results are relevant for investigations of diffusive shock acceleration.