Temporal evolution of photospheric vertical current (I_z). Panel a: same as Fig. 9a, except the B_z contours. Two regions specified as ‘A’ and ‘B’ are enclosed by the pink contours. The orange-coloured five-pointed star indicates the LCO. Panel b: temporal evolution of maximum and minimum vertical currents within the whole active region. Panels c and d: temporal evolution of total positive and negative photospheric vertical currents within the regions marked by ‘A’ and ‘B’, respectively. Panel e: GOES 1−8 and 0.5−4 Å channels SXR light curves.