Measurements of the geoelectric field component (North–South or East–West), the variation of the horizontal component (H) of the magnetic field and GIC (in amps) for 25–26 August 2018. Only one electric channel at each site was available. (a) Lerwick; (b) Eskdalemuir; (c) Hartland; (d) GIC from Torness substation, East Scotland. Note the magnetic and geoelectric curves are offset from zero.