More info on filaments:
"Filaments are formed in magnetic loops that hold relatively cool, dense gas suspended above the surface of the Sun," explains David Hathaway, a solar physicist at the NASA Marshall Space Flight Center. "When you look down on top of them they appear dark because the gas inside is cool compared to the hot photosphere below. But when we see a filament in profile against the dark sky it looks like a giant glowing loop -- these are called prominences and they can be spectacular."
this and more at:
http://spaceweather.com/glossary/filaments.html
Our Sun just amazes me
-E