Sun plasma loops. Coloured ultraviolet TRACE sate- llite image of part of the sun's surface with plasma loops. The surface (lower frame) is mostly at a temperature of 6000 degrees Celsius and is relatively cool (dark). Above the surface however, the bright loops of highly ionised iron atoms are at temperatures of around 1 million degrees Celsius. These plasma loops arise from active areas on the solar surface and follow the paths of powerful magnetic fields. TRACE (Transition Region and Coronal Explorer) studies the relationship of the magnetic fields to the plasma eruptions which sometimes affect Earth. This is one of TRACE's first images, taken on 24 April 1998.