Left panel: A copy of the upper panel of Figure 2 in B2008. The figure illustrates calculated regression coefficients showing lead–lag variations of Δp at mlat >83° S. It shows three cycles of IMF B_y, where the dark blue line represents the regression coefficients without any lag, while x and o cyan lines represent a −27 and +27 day lag between IMF B_y and Δp data series. All maxima in Δp are seen to occur −2 days before the peak in the IMF driver, which occurs at day 0. Right panel: Lead–lag variations of ΔZ_g at mlat >70° S. The blue line is the calculated regression coefficients showing lead–lags when the five bin method by B2008 is used. The red line is the regression coefficients showing lead–lag variations when regression is done without the initial grouping. Negative days (leads) represent ΔZ_g occurring before the B_y component, and positive days B_y occurring before ΔZ_g. Dots indicate significance at the 95% level for the regression coefficients calculated by Student’s t-test. The upper panel of Figure 2 in B2008 is reproduced with permission from John Wiley and Sons.