The annual and semi-annual variations in geomagnetic indices and estimated power input into the magnetosphere, P _α , for coincident data from 1995 to 2017, inclusive. In each panel the coloured line shows mean values of daily means of the geomagnetic index in 30 equal-width bins of time-of-year, F, smoothed with a 3-point running mean. The black line is the best-fit variation of the near-continuous P _α data for the same interval processed the same way. (a) is for the Ap index; (b) is for the Aa_H index, and (c) is for the Am index. In each panel, two goodness of fit metrics are given: the correlation coefficient r and the Root Mean Square (RMS) fit residual, ε, as a ratio of the overall mean value of the index.