Solar activity and differential rotation

The coronal sidereal rotation rate as a function of latitude for each year, extending from 1992 to 2001 for soft X-ray images and from 1998 - 2005 for radio images are obtained. The present analysis reveals that the equatorial rotation rate of the corona is comparable to the photosphere and the chromosphere, However, at the higher latitudes, the corona rotation quite differently than the photosphere and chromosphere. The latitude differential obtained by both radio and X-ray images is quite variable throughout the period of the study. The equatorial rotation period seems to vary almost systematically with sunspot numbers which indicates its dependence on the phases of the solar activity cycle.