From 2001From -2008, we use full-disk, SOHO/EIT 195 Å calibrated images to determine latitudinal and day-to-day variations of the rotation rates of coronal holes (CHs). We estimate the weighted average of heliographic coordinates such as latitude and longitude from the central meridian on the observed solar disk. For different latitude zones between 40• north and 40• south, we compute rotation rates and find that, irrespective of their area, the number of days observed on the solar disk, and their latitudes, CHs rotate rigidly. Combined for all the latitude zones, we also find that CHs rotate rigidly during their evolution history. In addition, for all latitude zones, CHs follow a rigid body rotation law during their first appearance. Interestingly, the average first rotation rate (∼438 nHz) of CHs, computed from their first appearance on the solar disk, matches the rotation rate of the solar interior only below the tachocline.

In the previous study (Hiremath, Astron. Astrophys. 452:591, 2006a), the solar cycle is modeled as a forced and damped harmonic oscillator and from all the 22 cycles , long-term amplitudes, frequencies, phases and decay factor are obtained. Using these physical parameters of the previous 22 solar cycles and by an autoregressive model, we predict the amplitude and period of the present cycle 23 and future fifteen solar cycles. The period of present solar cycle 23 is estimated to be 11.73 years and it is expected that onset of next sunspot activity cycle 24 might starts during the period 2008.57 ± 0.17 (i.e., around MaySeptember 2008). The predicted period and amplitude of the present cycle 23 are almost similar to the period and amplitude of the observed cycle. With these encouraging results, we also predict the profiles of future 15 solar cycles. Important predictions are: (i) the period and amplitude of the cycle 24 are 9.34 years and 110 (±11), (ii) the period and amplitude of the cycle 25 are 12.49 years and 110 (±11), (iii) during the cycles 26 (sun might experience a very high sunspot activity, (iv) the sun might also experience a very low (around 60) sunspot activity during cycle 31 (2089-2100 AD) and, (v) length of the solar cycles vary from 8.65 years for the cycle 33 to maximum of 13.07 years for the cycle 35.

Abstract. From 103 years of data of non-recurrent sunspot groups and for the two sets (area <100 millionths of hemisphere and >100 millionths of hemisphere), irrespective of their life span, we compute rotation rates and rate of change of rotation rates during their lifetime. It is found that variation of rotation rates of sunspot groups with respect to their lifetime is approximately similar to the radial variation of internal rotation inferred by helioseismology and it is confirmed that all the spot groups decelerate as they evolve into later phases of their lifetime. After classification according to different life spans, for the same two data sets, we compute initial rotation rates and rate of change of initial rotation rates of sunspot groups. For the two data sets, variation of initial rotation rates of sunspot groups with respect to their life spans is similar to the radial variation of internal rotation of solar plasma inferred from helioseismology. We also obtain the rate of change of initial rotation rates for two sets of spot groups and the results are as follows: (i) for the area <100, spot groups are accelerated for the life spans of 6-12 days and decelerated for the life spans of 3-6 days; (ii) for the area >100, acceleration for the life spans of 9-12 days and deceleration for the life spans of 3-9 days. Interpreting these results, an attempt is made to locate the sites of origin of spot groups of different sizes and life spans in the convection zone.

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