Variations in the period of the sunspot cycle

Using a wavelet analysis approach, subtle variations in the solar cycle period were extracted from the yearly means of the sunspot numbers. For the nominal eleven-year solar cycle, the resulting estimates of the cycle's period are in good agreement with those given by Friis-Christensen and Lassen. Longer period structures in the solar-cycle, including the Gleissberg cycle, are also delineated by the wavelet analysis.