5.3 The Gleissberg Cycle

Numerous authors have noted multi-cycle periodicities in the sunspot cycle amplitudes. Gleissberg (1939Jump To The Next Citation Point) noted a periodicity of seven or eight cycles in cycle amplitudes from 1750 to 1928. While Garcia and Mouradian (1998) suggest that a third period of this cycle can be found in the sunspot data, others (Hathaway et al., 1999Jump To The Next Citation Point) suggest that the period is changing or (Rozelot, 1994Ogurtsov et al., 2002) that it consists of two different components (one with a 90 – 100 year period and a second with a 50 – 60 year period). A simple sinusoid fit to the residual cycle amplitudes when the secular trend is removed now gives a 9.1 cycle periodicity. This best fit is shown in Figure 34View Image.
View Image

Figure 34: The Gleissberg Cycle. The best fit of cycle amplitudes to a simple sinusoidal function of cycle number is shown by the solid line (which includes the secular trend).

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