A New Method for Prediction of Peak Sunspot Number and Ascent Time of the Solar Cycle

Abstract

The purpose of the present study is to develop an empirical model based on pre- cursors in the preceding solar cycle that can be used to forecast the peak sunspot number and ascent time of the next solar cycle. Statistical parameters are derived for each solar cycle using "Monthly" and "Monthly smoothed" (SSN) data of international sunspot number (Ri). Primarily the variability in monthly sunspot number during different phases of the solar cy- cle is considered along with other statistical parameters that are computed using solar cycle characteristics, like ascent time, peak sunspot number and the length of the solar cycle. Us- ing these statistical parameters, two mathematical formulae are developed to compute the quantities (QC)n and (L)n for each nth solar cycle. It is found that the peak sunspot number and ascent time of the n + 1th solar cycle correlates well with the parameters (QC)n and (L)n/(SMax)n+1 and gives a correlation coefficient of 0.97 and 0.92, respectively. Empiri- cal relations are obtained using least square fitting, which relates (SMax)n+1 with (QC)n and (Ta)n+1 with (L)n/(SMax)n+1. These relations predict a peak of 74 ± 10 in monthly smoothed sunspot number and an ascent time of 4.9 ± 0.4 years for Solar Cycle 24, when Novem- ber 2008 is considered as the start time for this cycle. Three different methods, which are commonly used to define solar cycle characteristics are used and mathematical relations de- veloped for forecasting peak sunspot number and ascent time of the upcoming solar cycle, are examined separately.