Morphology and evolution of photospheric vertical current (I_z). Panel a: photospheric vertical current (I_z) map of the active region NOAA 12297. Contours of the z-component of a co-temporal vector magnetogram are plotted in panel a. The contour levels are ±300 G with the black and pink contours referring to positive and negative polarity magnetic fields, respectively. Two regions characterised by strong currents are enclosed by the black and the red boxes. The orange-coloured five-pointed star indicates the LCO. Panels b–g: representative I_z-maps of the regions enclosed by the black box showing the evolution of I_z during the interval of our analysis. The pink arrow in panel b indicates a location characterised by extreme close proximity of opposite polarity currents. The oval shapes in panels b–g enclose a positive I_z region which undergoes decay prior to the onset of the flare but grows following the event. Panels h–j: brief evolution of I_z-maps of the region encircled by the red box in panel a. The pink oval in these panels encircle a negative current region which undergoes significant changes during the interval of our analysis.