With time-lapse photography of the corona one sees spectacular motions of towering masses of luminous gas, called prominences. Projected against the solar disk, they are the dark, threadlike filaments. Their forms vary from almost stationary, quiescent arches and graceful loops to rapidly moving surges.
The typical prominence is hundreds of thousands of kilometers long and extends several tens of thousands of kilometers above the photosphere. It consists of gas cooler and denser than that in the corona around it. In the more active prominences, gas may rise at rates of hundreds to thousands of kilometers per second, which is sufficient to escape from the Sun. Frequently, however, matter appears to rain down from the corona in great luminous masses. Apparently, magnetic fields hold up these huge walls of gas against the Sun's gravitational pull. We can see matter flowing along the body of a prominence, following the curving and looping magnetic lines of force.
The mean lifetime of large quiescent prominences is about two to three rotations of the Sun. During sunspot maximum, 20 filaments may appear on the disk; during sunspot minimum, there are typically about 4. Prominences always appear to be associated with a plage or sunspot group. In fact, the large quiescent prominences tend to form along the division between regions of different magnetic polarity in plages. The polarity of each side of the plage region is also the same as that of the sunspots in the photosphere underneath it.