Prediction of solar activity on the basis of spectral characteristics of sunspot number

Prediction of solar activity strength for solar cycles 23 and 24 is performed on the basis of extrapolation of sunspot number spectral components. Sunspot number data during 1933-1996 periods (solar cycles 17-22) are searched for periodicities by iterative regression. The periods significant at the 95% confidence level were used in a sum of sine series to reconstruct sunspot series, to predict the strength of solar cycles 23 and 24. The maximum peak of solar cycles is adequately predicted (cycle 21: 158&plusmn;13.2 against an observed peak of 155.4; cycle 22: 178<&plusmn;13.2 against 157.6 observed). Solar cycle 23 was predicted to have a peak in 2000 with maximum amplitude of 125&plusmn;13.2, in good agreement with the 119.6 observed. The minimum of solar cycle 23 is predicted to occur around 2007-2008. For solar cycle 24, the maximum is predicted to occur in 2012 (115&plusmn;13.2) or 2013 (117&plusmn;13.2) and this shall be a very weak solar cycle