---
abstract: 'Propagation of energetic particles across the mean field direction in
  turbulent magnetic fields is often described as spatial diffusion. Recently, it
  has been suggested that initially the particles propagate systematically along meandering
  field lines, and only later reach the time-asymptotic diffusive cross-field propagation.
  In this paper, we analyse cross-field propagation of 1-100 MeV protons in composite
  2D-slab turbulence superposed on a constant background magnetic field, using full-orbit
  particle simulations, to study the non-diffusive phase of particle propagation with
  a wide range of turbulence parameters. We show that the early-time non-diffusive
  propagation of the particles is consistent with particle propagation along turbulently
  meandering field lines. This results in a wide cross-field extent of the particles
  already at the initial arrival of particles to a given distance along the mean field
  direction, unlike when using spatial diffusion particle transport models. The cross-field
  extent of the particle distribution remains constant for up to tens of hours in
  turbulence environment consistent with the inner heliosphere during solar energetic
  particle events. Subsequently, the particles escape from their initial meandering
  field lines, and the particle propagation across the mean field reaches time- asymptotic
  diffusion. Our analysis shows that in order to understand solar energetic particle
  event origins, particle transport modelling must include non-diffusive particle
  propagation along meandering field lines.'
adsnote: Provided by the SAO/NASA Astrophysics Data System
adsurl: https://ui.adsabs.harvard.edu/abs/2017MNRAS.470.3149L
archivePrefix: arXiv
authors:
- T. Laitinen
- S. Dalla
- D. Marriott
category: publications
date: '2017-09-01'
doi: 10.1093/mnras/stx1509
draft: false
eprint: '1706.06580'
featured: false
journal: MNRAS
month: September
number: '3'
pages: 3149-3158
primaryClass: physics.space-ph
projects: []
publication: MNRAS
publication_types:
- '2'
tags:
- Diffusion
- Magnetic fields
- Turbulence
- 'Sun: particle emission'
- Physics - space physics
- Astrophysics - solar and stellar astrophysics
title: 'Early propagation of energetic particles across the mean field in turbulent
  plasmas'
type: ARTICLE
volume: '470'
year: '2017'
---