Simulating Heliospheric and Solar Particle Diffusion using the Parker Spiral Geometry

TL;DR

This paper uses numerical Monte-Carlo simulations to study cosmic ray diffusion in the curved Parker spiral magnetic field of the Solar system, incorporating turbulence effects to better understand particle transport.

Contribution

It introduces a method to redefine diffusion coefficients in curved magnetic fields and incorporates turbulence effects using a WKB approach in test-particle simulations.

Findings

Redefinition of parallel and perpendicular diffusion coefficients for curved magnetic fields.

Quantitative analysis of the effects of magnetic field curvature on cosmic ray diffusion.

Assessment of turbulence influence on particle transport in the Solar system.

Abstract

Cosmic Ray transport in curved background magnetic fields is investigated using numerical Monte-Carlo simulation techniques. Special emphasis is laid on the Solar system, where the curvature of the magnetic field can be described in terms of the Parker spiral. Using such geometries, parallel and perpendicular diffusion coefficients have to be re-defined using the arc length of the field lines as the parallel displacement and the distance between field lines as the perpendicular displacement. Furthermore, the turbulent magnetic field is incorporated using a WKB approach for the field strength. Using a test-particle simulation, the diffusion coefficients are then calculated by averaging over a large number of particles starting at the same radial distance from the Sun and over a large number of turbulence realizations, thus enabling one to infer the effects due to the curvature of the magnetic fields and associated drift motions.