The Schwabe and Gleissberg Periods in the Wolf Sunspot Numbers and the Group Sunspot Numbers

Abstract

Three wavelet functions: the Morlet wavelet, the Paul wavelet, and the DOG wavelet have been respectively performed on both the monthly Wolf sunspot numbers (R _z ) from January 1749 to May 2004 and the monthly group sunspot numbers (R _g ) from June 1795 to December 1995 to study the evolution of the Gleissberg and Schwabe periods of solar activity. The main results obtained are (1) the two most obvious periods in both the R _z and R _g are the Schwabe and Gleissberg periods. The Schwabe period oscillated during the second half of the eighteenth century and was steady from the 1850s onward. No obvious drifting trend of the Schwabe period exists. (2) The Gleissberg period obviously drifts to longer periods the whole consideration time, and the drifting speed of the Gleissberg period is larger for R _z than for R _g . (3) Although the Schwabe-period values for R _z and R _g are about 10.7 years, the value for R _z seems slightly larger than that for R _g . The Schwabe period of R _z is highly significant after the 1820s, and the Schwabe period of R _g is highly significant over almost the whole consideration time except for about 20 years around the 1800s. The evolution of the Schwabe period for both R _z and R _g in time is similar to each other. (4) The Gleissberg period in R _z and R _g is highly significant during the whole consideration time, but this result is unreliable at the two ends of each of the time series of the data. The evolution of the Gleissberg period in R _z is similar to that in R _g .