Solar cycle 25 prediction using length-to-amplitude relations

Abstract

We propose a simple method for prediction of the 11-year solar cycle maximum that is based on two relations. One of them is well known Waldmeier's rule that binds the amplitude of a cycle and the length of its ascending phase. The second rule relates the length of a given cycle from minimum to minimum and the amplitude of the next one. Using corresponding linear regressions we obtain for the amplitide of cycle 25 in the scale of 13-month smoothed monthly total revised sunspot number ${\rm SN}_{\rm max}(25) = 181\pm46$ and for the moment of the maximum $T_{\rm max}(25) = 2024.2\pm1.0$. Therefore, according to the prediction, cycle 25 will be higher than the previous one (${\rm SN}_{\rm max}(24) = 116$) with probability 0.92.