Periodicities in solar activity

Abstract

The techniques of power spectral analysis are used to determine significant periodicities in the annual mean relative sunspot numbers. The main conclusion is that a period of 10.45 yr is very basic and can be associated with an excitation of new solar cycles. When combined with a period of 11.8 yr, associated here with the free-running length of a solar cycle, the mean cycle length of 11.06 yr and a phase variation of 190 yr are explained. Similarly the amplitude variations with periods 88 and 59 yr (previously described as the 80-yr cycle) are due to an amplitude modulation of the solar cycle by a period of 11.9 • 0.3 yr. The results dispute several associations of planetary position and solar activity.

Sunspot variability and an attempt to predict solar cycle 23 by adaptive filtering

“…They listed some significant oscillations separately for the 1749-1971 and 1845-1971 epochs and found that the two segments have no common periodicity except one with a period of 9.7 yr. Their list does not include two of the three fundamental periods identified here except the one close to 11.1 yr. Quasiperiodic fluctuations with 9.7 and 11.0 or 11.1 yr. periodicity were earlier reported by Currie (1973) and Cohen and Lintz (1974). In contrast, Cole (1973) concluded that the 10.45 yr oscillation is a basic mode associated with the excitation of the new solar cycle while a 11.8 yr. period could be associated with the free-running length of the solar cycle. He also detected 88 yr. and 59 yr. periodicities which he attributed to the amplitude modulation of the solar cycle by a period of 11.9 ± 0.3 yr.…”

“…In the analysis of the sunspot data, either a quasi-periodic behaviour is presumed and the components extracted through Fourier transform (Cole, 1973;Cohen and Lintz, 1974 and others) or it is treated as an autoregressive process and the spectrum is evaluated through Maximum Entropy Method (Currie, 1973;Kane and Trivedi, 1985 and others). Some authors describe the shape of the solar cycle in terms of smoothly varying functions with suitable parameters to control the shape of ascent to maximum and the descent to minimum (Hathaway et al, 1994 and references therein).…”

New Little ICE Age Instead of Global Warming?

“…Brier (1979) found a period of just 83 years in the unsmoothed cosine transform of 2148 autocorrelations of 2628 monthly sunspot numbers. Cole (1973) confirmed this result when he investigated the power spectrum of sunspot data covering 1626 -1968. He found a dominant peak at 84 years.…”

Periodicities in the ?10 cm solar flux

“…If the 1152 day periodicity is any measure of solar activity, then it is clear that some change did occur. Finally Cole (1973) and Wolff (1976) have suggested that an analysis of sunspot numbers shows basic periods of solar activity of 10.45 + 0.135 years and 11.9 years, and that harmonics of these can produce periodicities near to about 3 years, or 1100 days. However, it seems unlikely that this is the cause of the feature that we observe since we would not expect changes to occur over time scales as short as 5 years, unless some other coupling device is at work.…”