Clock plots of dH/dt for the first (upper row, events (a)–(c)) and second intervals (lower row, events (d)–(f)), indicating the MLT orientation of maximum variation. Red lines indicate the dH/dt for each event observed at northern hemisphere sites, and blue for the New Zealand site. Approximate MLT zones of extreme dH/dt associated with DP1 and DP2 current systems (Freeman et al., 2019) are shown by dark and light grey shading respectively.