Sunspots are dark, irregularly shaped areas which can sometimes be observed on the surface of the sun. They appear dark because they are about 2000° C cooler than the surrounding sun's surface. Their strong magnetic field inhibits convection of heat to the surface. Sunspots can vary in size from 16 km to 160,000 km.
Sunspot activity goes up (from minimum to maximum) and down (from maximum to minimum) in an eleven year cycle. Communication systems on earth and satellites are affected by sunspot activity.
Sunspots often appear in pairs in which one is like the north pole of a magnet and the other is like the south pole of a magnet. The two poles (sunspots) are linked by loops of magnetic field which arch through the sun's corona.
