Periodicities of solar flare and its relations

Daily flare index during period between March 1975 and May 1978, were studied by using power spectral analysis method. There are periodicities between 4.5 days to 21.7 days. Our results confirm the periodicity around 12.5 days found by several authors. This periodicity was attributed to the rotation of solar core. Long term periodicities were given where 88 and 320 days periodicities were confirmed. The relation between these periodicities and other solar activities periodicity were given.