---
abstract: 'Context. Diffusive shock acceleration in the solar corona can accelerate
  solar energetic particles to very high energies. Acceleration efficiency is increased
  by entrapment through self-generated waves, which is highly dependent on the amount
  of accelerated particles. This, in turn, is determined by the efficiency of particle
  injection into the acceleration process. \textbackslash Aims: We present an analysis
  of the injection efficiency at coronal shocks of varying obliquity. We assessed
  injection through reflection and downstream scattering, including the effect of
  a cross-shock potential. Both quasi-thermal and suprathermal seed populations were
  analysed. We present results on the effect of cross-field diffusion downstream of
  the shock on the injection efficiency. \textbackslash Methods: Using analytical
  methods, we present applicable injection speed thresholds that were compared with
  both semi-analytical flux integration and Monte Carlo simulations, which do not
  resort to binary thresholds. Shock-normal angle \ensuremath\theta$_Bn$ and
  shock-normal velocity V$_s$ were varied to assess the injection efficiency with
  respect to these parameters. \textbackslash Results: We present evidence of a significant
  bias of thermal seed particle injection at small shock-normal angles. We show that
  downstream isotropisation methods affect the \ensuremath\theta$_Bn$-dependence
  of this result. We show a non-negligible effect caused by the cross-shock potential,
  and that the effect of downstream cross- field diffusion is highly dependent on
  boundary definitions. \textbackslash Conclusions: Our results show that for Monte
  Carlo simulations of coronal shock acceleration a full distribution function assessment
  with downstream isotropisation through scatterings is necessary to realistically
  model particle injection. Based on our results, seed particle injection at quasi-parallel
  coronal shocks can result in significant acceleration efficiency, especially when
  combined with varying field-line geometry. \textbackslash\textbackslashAppendices
  are available in electronic form at <A href=``http://www.aanda.org''''>http://www.aanda.org</A>'
adsnote: Provided by the SAO/NASA Astrophysics Data System
adsurl: https://ui.adsabs.harvard.edu/abs/2013A&A...558A.110B
archivePrefix: arXiv
authors:
- M. Battarbee
- R. Vainio
- T. Laitinen
- H. Hietala
category: publications
date: '2013-10-01'
doi: 10.1051/0004-6361/201321348
draft: false
eid: A110
eprint: '1309.2062'
featured: false
journal: A&A
month: October
pages: A110
primaryClass: astro-ph.SR
projects: []
publication: A&A
publication_types:
- '2'
tags:
- Acceleration of particles
- Shock waves
- 'Sun: coronal mass ejections (CMEs)'
- Astrophysics - solar and stellar astrophysics
title: 'Injection of thermal and suprathermal seed particles into coronal shocks
  of varying obliquity'
type: ARTICLE
volume: '558'
year: '2013'
---