Robert and Karl Wood [18] showed that the jerk (derivative of acceleration) caused by planets' attraction presented some strong maxima, and that some of these maxima were in good correlation with local peaks of the sunspot numbers. They also showed that no long term correlation can be found using this method.

P. Jose [8] showed that some agreement could be found between the sunspot cycle and the 12 years period of Jupiter when additionnal effect of other planets was included.

E.K. Bigg [3] published on the influence of Mercury through solar tides on the sunspot cycles.

Michel Trellis [15] established strong statistical correlations between gravitational tides at the Sun's surface, sunspot numbers and the rate of birth of active centers. He published a mathematical model of the solar surface tide, concluding that, as the calculated amplitude of the tides was very small (a few millimeters), a deeper mechanism should be imagined to explain the huge energy involved in the solar activity cycle.

Theodor Landscheidt [10] worked on the moves of the Sun around its center of mass and found also some local correlations and a 12 years periodicity, which in fact can be related mainly to the anomalistic period of Jupiter. Local correlations can also be found, corresponding to the periods where the 12 years Jupiter period is in proper phase with the sunspot cycle, but the model fails to explain long term data : it had especially predicted a small amplitude for cycle 22.

G. Brown made a review of these type of works in a survey paper [5] at the Meudon Symposium (SolarTerrestrial Predictions), remarking that all of these failed to establish reliable long term prediction models.

Wilson [17]has shown that the period of the 11 years cycle has a bimodal distribution, with two mean values at 122 and 140 month.

Berger et al. [2] showed with frequency analyses that the 22 years magnetic cycle has been perfectly stabled in frequency and phase for 300 years. On the contrary, the 11 years sunspot cycle embedded in it shows phase shifts which seem to be correlated with amplitude variations.

Williams and Sonett published a paper on a geologic formation of Australia : the Elatina varves [16]. A varve is a thin layer that can be seen in the geologic formation. In this case, it can be found, in a regular varve accumulation, a signal derived from varve thickness which looks like the actual solar cycle Wolf number, with more regularity.

Bracewell [4] made a mathematical model of the sunspot cycle, taking the Wolf number positive if the cycle number is even, negative if it is odd. He finds by a Laplace analysis a sinusoidal 22 years period carrier modulated by an enveloppe function, having a fundamental period around 300-350 years, and an other periodic component at 157 years. The curve of Fig. 1 shows the "signed Wolf number" on which his analysis was made. He pointed out also that the 22 years period of this pseudomagnetic cycle is monomodal, and has a lower standard deviation than the 11 years sunspot cycle.

His analyses induced me to think that the modulation effect found in the Elatina formation still exists now, but with a different waveform shape, and different periods. I was conducted to search for an oscillation mechanism which could give either a resulting signal like the Elatina's one, or like Bracewell's simulation results (Fig. 1) . The perfect shape of the first pushed me to search in the old works on planetary moves, looking for a possible excitation source to solar cycles.

I received this from Ray Tomes's "Cycles" Mailing list :

"I received an email from Timo Niroma

He has done a lot of work analysing sunspot periods and presents the
results in a very clear manner. He is particularly interested in the
presence of a period of 11.84 years which he attributes to Jupiter's
11.86 year orbital period as the phase matches Jupiter's aphelion /
perihelion. Recommended for anyone interested in sunspots."

Very interesting site, clearly presented. I want to do now some research to add the "anomalistic cycle" of Jupiter as a modulating effect to my VE-EA-JU syzygie cycle (see next pages). Thanks to Timo Niroma...