prominence

A term used for a variety of cloud- and flame-like structures in the chromosphere and corona of the Sun, all of which have a higher density and lower temperature than their surroundings. When seen on the solar limb they appear as bright features in the corona, and when seen in projection against the disc they appear as dark filaments. Quiescent prominences occur away from active regions and are stable with lifetimes of many months. They may extend upwards for tens of thousands of kilometres. Active prominences are associated with sunspots and flares. They appear as surges, sprays and loops, have violent motions, fast changes and lifetimes of up to a few hours. Cooler material flowing back from prominences in the corona to the photosphere may be observed as coronal "rain".