Analytical separator model (Threlfall et al. 2015b); a) initial positions (closeup around separator) and b) final positions for electrons with initial pitch angle 45° and initial kinetic energy of 20 eV. c) and d) are the same, but for protons. The colour of each particle identifies the (scaled) peak kinetic energy gained during each orbit (see colour bar). For b) and d) thin pink/purple lines are field lines in the fan planes associated with the upper/lower nulls (indicated by trapezoids) and thick pink/purple lines indicate the corresponding null’s spine. Also in these graphs, to aid visualisation, the orb size for each particle has been enhanced in proportion to its final energy. For reference, b_scl = 10 G, l_scl = 10 Mm, and t_scl = 100 s for these orbit simulations.