The Sun has 11 –year cycles of sunspot activity due to changes in its magnetic field. The increased surface activity means that more changed solar particles reach Earth’s atmosphere, causing radio interference and aurora. Nuclear reactions in the Sun’s core send waves of energy flowing to the surface, where it is given off as light, heat and other radiation.The Sun’s diameter is 1,392,000 km (865,000 miles). More than one million Earths would fit inside the Sun.