Variations with fraction of a calendar year, F, for the two polarities of the IMF B_Y in the GSEQ frame. Normalised mean values, 〈X〉_F/X_max, are shown in bins 1/36 yr wide, with open circles being for [B_Y]_GSEQ > 0 and solid triangles are for [B_Y]_GSEQ < 0. The data are for the interval 1996–2018. 〈X〉_F is the mean in each bin of F and X_max is the largest value of 〈X〉_F for a generic parameter X. The blue lines are for the am index; the mauve lines are for the half-wave rectified southward IMF, B_S; the black lines are for the power input to the magnetosphere, P_α; the orange line is the half-wave rectified southward field predicted for the R-M effect with IMF clock angle [θ]_GSEQ = 90°, [B_S]_RM: [B_S]_RM = b − [B_Z]_RM for [B_z]_RM< 0 and [B_S]_RM = b for [B_Z]_RM > 0: and where b is the best-fit baselevel value for northward IMF in GSM and [B_Z]_RM = [B_Y]_GSEQ sin(β_GSEQ) is the northward field in GSM obtained by assuming [θ]_GSEQ = 90°, β_GSEQ being the rotation angle between the GSEQ and GSM frames.