The growth rate of solar activity in the early phase of a solar cycle has been known to be well correlated with the subsequent amplitude ( solar maximum ) .
It provides very useful information for a new solar cycle as its variation reflects the temporal evolution of the dynamic process of solar magnetic activities from the initial phase to the peak phase of the cycle .
The correlation coefficient between the solar maximum ( \beta _ { \mathrm { a } } ) and the rising rate ( \beta _ { \mathrm { a } } ) at \Delta m months after the solar minimum ( R _ { \mathrm { min } } ) is studied and shown to increase as the cycle progresses with an inflection point ( r = 0.83 ) at about \Delta m = 20 months .
The prediction error of R _ { \mathrm { max } } based on \beta _ { \mathrm { a } } is found within estimation at the 90 % level of confidence and the relative prediction error will be less than 20 % when \Delta m \geq 20 .
From the above relationship , the current cycle ( 24 ) is preliminarily predicted to peak around October , 2013 with a size of R _ { \mathrm { max } } = 84 \pm 33 at the 90 % level of confidence .