Annual variations in geomagnetic indices and power input into the magnetosphere: (left) the Aa_H index means for 1868–2017; (middle) Dst index (1959–2017) and (right) daily the power input into the magnetosphere P_α (1995–2017). In the top panels, the black lines show the mean values in 36 equal-width bins of fraction of time-of-year, F (roughly 10 days width) and the grey areas are plus and minus one standard deviation: (a) 〈Aa_H〉; (b) 〈Dst〉; and (c) 〈P_α〉. The lower panels show the variation of the number of days in which the daily means exceed the (blue) 90-percentile, (orange) 95-percentile, and (mauve) 99-percentile (d), (e) and (f) being for Aa_H, Dst and P_α, respectively. The thin vertical lines mark the equinoxes (the times of the peaks in the equinoctial variation) and the grey and cyan are variations predicted by the Russell-McPherron and equinoctial effect, respectively, scaled in amplitude to match the observed variations so as to reveal waveform and phase differences.