Comparison of conductivity-corrected and modelled UT variations for (red) northern hemisphere, (blue) southern hemisphere, and (black) global aσ indices. Each panel compares the conductivity corrected values (solid lines) and the modelled values (dot-dash lines) on the same plot, as in Figure 18d. (a) For dawn, aσ_Ncc(dawn), aσ_Scc(dawn) and aσ_cc(dawn) compared with aσ_Nm(dawn), aσ_Sm(dawn) and aσ_m(dawn); (b) for noon, aσ_Ncc(noon), aσ_Scc(noon) and aσ_cc(noon) compared with aσ_Nm(noon), aσ_Sm(noon) and aσ_m; (c) for dusk, aσ_Ncc(dusk), aσ_Scc(dusk) and aσ_cc(dusk) compared with aσ_Nm(dusk), aσ_Sm(dusk) and aσ_m(dusk); and (d) for midnight, aσ_Ncc(midn), aσ_Scc(dusk) and aσ_cc(dusk) compared with aσ_Nm(midn), aσ_Sm(midn) and aσ_m(midn).