|A 'mega-cool' filament|
|An extremely large filament is visible on the solar disk. The length of the filament is even more then 60 times the diameter of Earth! At the moment, the plasma structure is quiet and not 'wobbling'.|
|Nederlandstalige versie /Version française||posted: february 22, 2005|
A filament is a cloud of plasma suspended above the solar surface. Magnetic arcades act as a hammock in which the plasma rests. The filament appears as a dark ribbon in pictures like H-alpha (visible light) since it absorbs radiation from the solar surface below it and redistributes it in all directions so that the net radiation coming towards us, is less.
If the magnetic field structure around the cooler plasma breaks open, the plasma can be thrown into space: this is a filament eruption and may lead to a CME.
The series of pictures above tells us where the filament is (SOHO/EIT304, orange) and where the footpoints of the magnetic arcades creating the plasma tube, are located (SOHO/MDI, black/white/grey). The filament is situated between a positive (white) and a negative (black) magnetic field area which are connected by the magnetic arcades.
The SOHO/EIT195 movie on the left (click on it) shows how the filament and its magnetic arcades behave. We use this to predict a possible outburst. The picture on the right is taken from a groundbased observatory in Catania in H-alpha and shows us the filament in all its glory.