Power Spectrum Analysis of Mount Wilson Solar Diameter Measurements: Evidence for Solar Internal r-mode Oscillations

This paper presents a power-spectrum analysis of 39,024 measurements of the solar diameter made at the Mount Wilson Observatory from 1968.670 to 1997.965. This power spectrum contains a number of very strong peaks. We find that eight of these peaks agree closely with the frequencies of r-mode oscillations for a region of the Sun where the sidereal rotation frequency is 12.08 year^-1. We estimate that there is less than one chance in 10⁶ of finding this pattern by chance.