Sunspot maximum data, R_max vs. geomagnetic index data aa_min. The latter have been taken from the standard time series (open circles, thin regression line) and the Lockwood time series (filled circles, thick regression line). The left- and right-hand panels are for the Regular Episode (sunspot cycles #9 to #25) and for the Grand Maximum (sunspot cycles #16 to #23), respectively. The abscissa values of the green (left) and the red (right) stars are our predictions from the standard aa_min data (De Jager & Duhau 2009) and for the Lockwood data (Duhau & De Jager 2010), respectively. The ordinate values are those of the corresponding open triangles in Figure 3. The error bar is included in the left-hand diagram.