Sun, sunspots and solar flares, illustration. Sunspots (upper right, lower left) are areas that temporarily appear dark on the surface of the Sun. They appear dark because they are cooler than other parts of the Sun?™s surface due to a very strong local magnetic field. Solar flares (lower left), or prominences, are dense clouds of plasma, or ionised gas, in the Sun's outer layer, the corona. Upon erupting, the flares become part of the solar wind. Sunspots appear within active regions, usually in pairs of opposite magnetic polarity.