Solar Physics

, Volume 30, Issue 1, pp 103–110 | Cite as

Periodicities in solar activity

  • T. W. Cole


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.


Spectral Analysis Solar Activity Solar Cycle Amplitude Modulation Cycle Length 
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Copyright information

© D. Reidel Publishing Company 1973

Authors and Affiliations

  • T. W. Cole
    • 1
  1. 1.Division of RadiophysicsCSIROSydneyAustralia

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