A strand of relatively cool (about 10,000 K) gas in the solar corona
seen as a bright structure above the Sun's limb
against the blackness of space. When the same feature is seen dark in projection
against the solar disk it is called a filament.
Prominences come in two broad classes: active and quiescent
(including quiet region filaments and active region filaments). An active
prominence changes in appearance over a few minutes and involves high-speed
material motion of up to 2,000 km/s. Active prominences are associated with
sunspots and solar
flares, can last up to several hours, and take the form of loop
prominences, sprays, and surges. Cooler material flowing back from prominences
may be seen as coronal rain.