Evidence of long-period solar velocity fluctuations

Evidence of a solar fluctiation with a period of 17atsup dat is observed in spectroscopic differential rotation data by using a technique developed to look at long time sequences of unevenly spaced data. Both spectroscopic observations and sunspot drift velocity measurements indicate a possible periodicity between 184 and 364atsup dat. The sunspot data marginally show fluctuations with periods which are multiples of 4atsup dat.2