Modelling of proton acceleration in application to a ground level enhancement A. Afanasiev, R. Vainio, A. P. Rouillard, M. Battarbee, A. Aran and P. Zucca A&A, 614 (2018) A4 Published online: 06 June 2018 DOI: 10.1051/0004-6361/201731343