Quasi ~500-year Cycle Signals in Solar Activity

Direct observations of solar activity are available for the past four century, so some proxies reflecting solar activity such as 14 C, 10 Be and geomagnetic variations are used to reconstruct solar activity in the past. In this present paper, the authors use rectified wavelet power transform and time-averaged wavelet power spectrum to investigate long-term fluctuations of the reconstructed solar activity series. Results show obvious a quasi ~500-year cycle exists in the past solar activity. Three reconstructed solar activity series from 14 C variations confirm the periodic signals.