Using the daily Mt. 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 timescales in the solar differential rotation. We represent the differential rotation in the form: omega(lambda) = (A) over bar + (B) over bar (5 sin(2) lambda - 1) + (C) over bar (21 sin(4) lambda - 14 sin(2) lambda + 1), using a set of Gegenbauer polynomials, where omega(lambda) is the angular velocity at latitude lambda. The coefficients (A) over bar, (B) over bar, and (C) over bar are free of crosstalk. We found that approximate to 9-day periodicity is statistically highly significant in the variations of (C) over bar at the maximum of solar cycle 22. A similar periodicity is found in the variations of (B) over 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) over bar, and this periodicity is found in (A) over bar during almost throughout the period 1986-1994. The approximate to 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. (C) 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.
