MOTIONS IN ARCH FILAMENT SYSTEMS

A new analysis of Hα filtergrams and Hα spectra of arch filament systems (AFS) shows that material flows downwards in both branches of the arch filaments (v ≈ 50 km/sec) while the top of the arches ascends (v ≲ 10 km/sec). It is suggested that AFS are produced by the magnetic field which expands, between growing spots, into higher levels carrying material with it that subsequently slides down along the magnetic field following gravity. AFS are also visible in the K line of Ca ii; however, there they appear less pronounced than in Hα and they are less conspicuous than the K-line quiescent filaments. There is some indication that AFS just cover a supergranulum (Ca network cell) with material streaming down at the border of the cell. No indication was found for a close relationship between AFS and flares. © 1969 D. Reidel Publishing Company.