Study of periodicity in sunspot numbers during solar cycle 23-24 using fast Fourier transform technique

We present here a study of long term periodicities and hemispheric periodicities in sunspot numbers (SSNs) during solar cycle 23 and 24. We have utilized Fast Fourier Transform (FFT) technique for the determination of periodicities. We found a long term periodicities of 3, 4, 6 and 12 years for SSNs when examined for cycle 23 and 24 combindly. We found short term periodicities corresponding to the solar rotational periods in the range of 25 to 36 days. We found mainly 26, 27, 28 and 36 days periodicities in this category. Other short term periods of 45 and 83 days were exhibited by SSNs. Rieger type periodicities of 112, 131, 133 and 182 days were observed for SSNs when studied for long term periodicities by taking the monthly time series. Annual period of 1 year and quasi Biennial periods of 1.5, 2 and 2.4 years were observed in this study of SSNs.