(a) The observed variations of the geomagnetic indices with fraction of year, F, shown as means in 36 equal-sized bins in F as a fraction of their overall mean: (red) an(F)/〈an〉_all; (blue) as(F)/〈as〉_all; and (black) am(F)/〈am〉_all. (b) The variations after correction for conductivity effects: (red) an_cc(F)/〈an_cc〉_all; (blue) as_cc(F)/〈as_cc〉_all; and (black) am_cc(F)/〈am_cc〉_all. The deviations of an and as from am, (red) Δan = an − am, (blue) Δas = as − am, which for these variations with F are taken to be due to conductivity effects alone. (d) The variations of (red points) Δan and (blue points) Δas as a function of the mean dipole tilt angle, ψ for the same F-UT. The black lines in (d) are 4th-order polynomial fits to the points that are used to correct an to an_cc and as to as_cc, using equations (6) and (9), respectively.