The sun’s activity follows an 11- years cycle, during with sunspot numbers build to a maximum and then decline again. After a time of sunspot minimum, when the surface many be completely unblemished, the first spots of the new cycle appear in mid latitudes. These gradually migrate towards the equator, while further spots continue to appear in the higher latitudes. At the same time flares and prominences become more numerous; prompted by the same fluctuation in the magnetic field, and the corona grows bigger. This continues for five or six years, after which the rate at which new spots appear gradually drops, and other forms of activity decline.
This characteristic movement of the sunspots across the Sun is positive proof that it spins. The cycle is caused by the progressive tangling and untangling of magnetic fields within the Sun, owing to the differential rates of rotation, with regions which are near to the poles taking a few days to complete their rotation than the equatorial areas. Unlike the planets, the whole mass does not spin at the same rate