Author:EdmondsAbstract:Rieger quasi-periodicities have been reported numerous times. However, no accepted explanation of the quasi-periodicities has emerged. We examine the possibility that the some of the reported periodicities are associated with a Mercury to Sun interaction of base period 88 days. To test this idea we filter the daily sunspot area record with band pass filters centred on the 88 day period and 176 day sub harmonic period of Mercury. We observed that the time variation of the amplitude of the components was comprised of episodes that varied in 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 filtered components was compared with the time variation of the tidal effect of Mercury. We were able to show that when episodes were discrete the time variation of the component of sunspot area during the episode was either in-phase or in anti-phase with the tidal effect. We interpret this result as an indication of a connection between planetary motion and sunspot emergence. When several discrete episodes of the 88 day or the 176 day period components occurred during a solar cycle the spectrum of sunspot area exhibited periodicities at sidebands to the 88 day or 176 day periods with the periodicity of the sidebands dependent on the duration of the episodes. A model based on amplitude modulation of 88 day and 176 day period sinusoids was able to consistently reproduce periodicities observed in the spectra of sunspot area. It is proposed that the observed connection between planetary motion and sunspot emergence involves magnetic Rossby waves with mode periods close to the sub harmonic periods associated with Mercury and the triggering of sunspot emergence by those Rossby waves.