Identification of nested active regions. Each panel corresponds to one of the horizontal bars from Fig. 1, i.e. an epoch of stalling in the reversal of the Sun’s dipole magnetic field. Data are combined from five CRs during each period, in a similar manner as for Figs. 2-4, to highlight regions with persistent EUV emission (background grey-scale) that restrict the position of the HCS (dashed coloured lines) and motion of the dipole axis (connected red dots). Black boxes highlight regions with repeated flux emergence that anchor the HCS above them.