Field distribution of magnetograms from simulations of active region formation S. Dacie, L. van Driel-Gesztelyi, P. Démoulin, M. G. Linton, J. E. Leake, D. MacTaggart and M. C. M. Cheung A&A, 606 (2017) A34 Published online: 04 October 2017 DOI: 10.1051/0004-6361/201730767