Early Forecast of a Maximum in the 25th Cycle of Solar Activity

Abstract

The statistical relation between the rate of increase in the number of sunspots at the initial phase of the growth curve (from 20th to 29th cycle months) and the cycle amplitude is considered on the basis of data on the 24 previous solar cycles. It has been concluded that the maximum smoothed number of sunspots for the 25th cycle must be equal to W_max(25) ≈ 206 in the case when the growth phase is monotonical and W_max(25) ≈ 160 in the case of its nonmonotonical character with a split top as in the 24th cycle. Both cases correspond to a moderate solar cycle obeying the Gnevyshev–Ohl rule. At such current cycle parameters, there are no signs of a coming deep secular cycle minimum in the middle of the 21st century.