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I found this fascinating quote today:
Paradoxically, prominences are cooler than the surrounding atmosphere. They are columns of sun-stuff trapped and held up in the magnetic fields above the solar surface. The trapped plasma cools, recombines into hydrogen atoms and then emits visible light to show up as a prominence. The glowing gas twists and swirls in the sway of the magnetic fields and can change its appearance from minute to minute.Peter Desypris, Corvus Eye Observatory- Syros,Greece, Jan 2010
You should read the whole article.