Short periodicities in solar activity

Several indices of solar activity are subjected to a high pass filter and power spectral analysis to verify the existance of shorter periodicities in solar activity. Though all these indices show the presence of short periodicities, above 95% confidence level, the common indices like sunspot number, fail to show these periodicities when a stringest statistical test is applied based on a percentage of the ²/v distribution that is appropriately higher than the 95% point (Mitchell et al., 1966). The basic parameters given by Kopecký (1967), however, reveal the presence of 5.6- and 3.5-yr periodicities even when this stringent statistical test is applied.