Energetics for case 1b (Table 1), with corresponding MHD fields shows in Fig. 4. At around 100t_A, the first stage of reconnection is slowing to a halt as islands reach saturation. At around 150t_A the large drop in magnetic energy (panel a) and spike in kinetic energy (panel b) correspond to the island coalesence event seen in Fig. 4 (panels e–f). The total energy is shown as an indication of numerical accuracy over the course of the simulation: the small initial rise is due to the driving at the boundary, remaining constant thereafter (observed in all simulations, witihin 5%).