The solar cycle: predicting the peak of solar cycle 25

Motivated by a successful prediction on the peak of solar cycle 24 (81.7, comparable to the observed 81.9, Du in Astrophys. Space Sci. 338:9, 2012 ), based on the logarithmic relationship between the maximum amplitude ( R m ) of a solar cycle and the preceding minimum a a geomagnetic index ( a a min ), we perform a prediction on the peak of the upcoming cycle 25 using the sunspot number of the new version instead. If the suggested error in a a (3 nT) before 1957 is corrected, the correlation between ln R m and ln a a min ( r = 0.92 ) is stronger than that not corrected ( r = 0.86 ). Based on this relationship, the peak value of cycle 25 is predicted to be R m ( 25 ) ≃ 151.1 ± 16.9 , about 30% stronger than cycle 24. Employing the ‘Waldmeier effect’ that the rise time of a cycle is well anti-correlated to its amplitude, we estimated the rise time, T a ( 25 ) = 4.3 ± 0.2 ± 0.6 , and the peak time of cycle 25, 2024.1 ± 0.8 (years), which is during April 2023 and November 2024.