Strong solar dipole minimum: cuts in the separatrix surfaces at fixed radii of a) r = R_ss = 2.5 R_⊙, b) r = 1.44 R_⊙ and c) r = 1.02 R_⊙. The magnetic topology features are coloured according to Fig. 5b and Table 1. The polar open-field regions are the only open-field regions present and are labelled OF_P1 and OF_N1. The one open separatrix curtain is labelled OSC while the separatrix cave in c) is labelled CAVE.