Mid-latitude magnitude GIC data from Scotland (Torness) and New Zealand (Halfway Bush) during Interval 1 on 7–8 September 2017. The times of coincident, large dH/dt events (a)–(c), determined from Figures 3 and 4, are plotted as vertical red dotted lines where they coincide with enhanced GIC levels. The times of local magnetic midnight (MN) and midday (MD) are shown on the panels. Note the factor of 10 difference in the y-axis scales.