Quasi 9 and 30-40 days periodicities in the solar differential rotation

Abstract

Using the daily Mount Wilson Doppler velocity data during 1986-1994 (solar cycle 22), we studied the short-term variations of the order of a few days to a month time scales in the solar differential rotation coefficients A-bar, B-bar and C-bar. We found that a ~9-day periodicity is statistically highly significant in the variations of C-bar at the maximum of solar cycle 22. A similar periodicity is found in the variations of B-bar during the descending phase of the cycle 22 with significant on > 99.9% confidence level. At this cycle maximum, a 30-40 day periodicity is found to be dominant among the variations in B-bar, and this periodicity is found in A-bar during almost throughout the period 1986-1994.The ~9-day periodicity in the variation of the differential rotation approximately matches with the known quasi 10-day periodicity in the total solar irradiance (TSI) variability. Hence, we speculate that there exists a relationship between the differential rotation and TSI variability. We suggest that the 9-10 day periodicities of the differential rotation and TSI have a relationship with the production and the emergence rates of the large-scale solar magnetic flux.