Variations in the sin⁴(θ_GSM/2) IMF orientation factor at a given (the GSEQ-to-GSM frame rotation angle) and (the IMF clock angle in the GSEQ frame). The plots are of Δsin⁴(θ_GSM/2), the difference in the value for the given by the x axis and for = 0: hence Δsin⁴(θ_GSM/2) quantifies the fractional variation in the solar-wind/magnetosphere coupling due to the R-M effect, positive values being increases. The mauve lines are for the UT effect and the annual (F) effects combined (due to the offset of Earth’s magnetic and rotational axes and the tilt of Earth’s rotational axis to the ecliptic plane, respectively) and the black segments are for the annual (F) variation alone. Each panel is for a different value of between 0 (purely northward IMF normal to the solar equator) and 180° (purely southward IMF normal to the solar equator).