Do Periodic Peaks in the Planetary Tidal ForcesActing Upon the Sun Influence the Sunspot Cycle?
A parameter that is indicative of the peak planetary tidal forces acting upon the Sun i.e. changes in the alignment of Jupiter, at the time of inferior and superior conjunctions of Venus and Earth, naturally exhibits characteristics that either mimic or replicate five of the main properties of the solar cycle. These properties include: the Schwabe cycle; the Hale cycle; the Gnevyshev−Ohl rule; the extended solar cycle; and the sunspot cycle's inherent memory. We believe that this result strongly supports the proposal by Hung (2007) that the solar sunspot cycle is being influenced by variations in the planetary tidal forces acting upon the Sun. This conclusion is supported by the fact that over the last thousand years, every time the peak planetary tidal forces acting upon the Sun are at their weakest there has been a period of low solar activity know as a Grand Solar minimum. The one exception to this rule is a period of weak planetary tidal peaks that roughly coincides with the Medieval Maximum in solar activity. We speculate that this one exception to the rule might have occurred because there was another countervailing factor present during the Medieval Maximum that was working against the planetary tidal effects. We note that the most recent period of weak planetary tidal peaks reached a maximum sometime in the 1990's, without any significant reduction in the level of solar activity. This leads us to conclude that the activity level on the Sun is either in early stages of an Oort−like minimum that will last from 2005−2045, or it is about half way through a period of high solar activity similar to the Medieval Maximum. We believe that evidence pointing towards a significant decrease in the level of sunspot activity in the upcoming solar cycles strongly favors the former conclusion.
A peak annual sunspot number of 87 ± 11 for cycle 24 is in good agreement with the predictions of 75 ± 8 made by Svalgaard et al.(2005) based upon the idea that strength of the polar field during the declining phase of one sunspot cycle is a good indicator of the peak sunspot number of the next cycle.