Surveys of electron and proton orbits, for initial position grid seen in Fig. 2a, subject to electric field reductions of a factor 10 (a)−b)) and 100 (c)−d)) from the original electric field (E_orig) determined by the MHD active region simulations. Final particle positions are colour-coded by peak energy (using the same colour bar as in Fig. 3 to enable direct comparisons) achieved during the orbit calculation lasting 10 s for electrons or 1000s for protons (or upon leaving the MHD simulation domain) with interpolated magnetic field lines (thin grey lines) included for reference.