A comparison of F-UT patterns of (right column) conductivity-corrected observed indices and (left column) the corresponding modelled pattern, the top row is for the northern hemisphere an index, (a) an_m and (b) an_cc = an/P_ΣN; the top middle row is for the southern hemisphere as index, (c) as_m and (d) as_cc = as/P_ΣS; the bottom row is for the global hemisphere am index, (e) am_m = (an_m + as_m)/2 and (f) am_cc = (an_cc + as_cc)/2. In all three cases the free fit parameter used is c_PM = 0.27, derived by minimising the r.m.s. fit residual for the am index case, {〈(am_cc − am_m)²〉}^1/2.