Are intermediate range periodicities in sunspot area associated with   planetary motion?
  In this paper we examine the possibility that intermediate range periodicities in sunspot area can be linked to Mercury or to Mercury-planet conjunction periods. We show that peaks at the 45 day Mercury-Jupiter conjunction period, the 116 day first harmonic period of the Mercury-Earth conjunction and the 289 day period of the sub harmonic Mercury-Venus/Mercury-Earth conjunctions are prominent in spectra of sunspot area. We observe two prominent peaks close to the 88 day Mercury periodicity and two prominent peaks close to the 176 day first sub harmonic of Mercury periodicity. To confirm that the peaks arise as sidebands we band pass filter the sunspot area record to isolate the 88 and 176 day components of sunspot area. The components occur in episodes of duration from 1.5 to 4 years, with successive episodes usually overlapping in time but, for significant intervals in the record, the episodes were discrete, i.e. not overlapping. The time variation of the components was compared with the time variation of the tidal effect of Mercury. We were able to show that whenever episodes were discrete the component of sunspot area during the episode was either in-phase or in anti-phase with the Mercury tidal effect. We interpret this as indicating a connection between planetary motion and sunspot emergence. When several discrete episodes of the components occurred during a solar cycle the spectrum of sunspot area during that solar cycle exhibited periodicities at sidebands to the 88 day or 176 day periods, the periodicity of the sidebands depending on the duration of the episodes. A simple model based on amplitude modulation of 88 day and 176 day period sinusoids was able to consistently reproduce the spectral peaks, or Rieger quasi-periodicities, observed in the spectra of sunspot area. 
Ian Edmonds
astro-ph.SR