Mass motions in a quiescent filament

The “disparition brusque” (DB) of a filament (N20, E35) has been observed above an active region with the Multichannel Subtractive Double Pass (MSDP) spectrograph operating on the Meudon Solar Tower, from 10h45 UT to 13h30 UT on June 22, 1981.Velocity fields and intensity fluctuations are measured in the Hα line. The DB doesn't take place simultaneously in all parts of the filament : thin threads (thickness <3 arc seconds) with upward radial velocities reaching about 50 km/s are successively observed inside the prominence from S to N regions. These motions correspond likely to the rise of material along magnetic loops closely related to the prominence structure. The dynamics inside such a magnetic loop is investigated : a high speed flow (supersonic, likely superalfvénic) strongly accelerated is evidenced and a deformation of the flux tube, probably due to the centrifugal forces exerted by the flow on the magnetic lines, is suggested.These results are compared with some theoretical works on dynamics inside magnetic loops, especially to siphon flow models. However, as in the case of the prominence support problem, better theoretical models are still needed.