<<c>

.....in this picture.</c>

Those dark, scat shaped regions on the disk of the sun called filaments are areas where there are magnetic fields above the surface of the sun that (counterintuitively for you plasma buffs) trap neutral Hydrogen and have a kind of buoyancy from the magnetic field pressure. These are usually the primary source of the matter found in CMEs (Coronal Mass Ejections). The idea is, as these filaments gain "altitude" and drag the magnetic field behind them causing a reconnection event which superheats the filament and surrounding region and blows it off the surface of the sun into interplanetary space.

I've never seen one this long before however.