PROFILES OF HI (L-ALPHA), MGII (H AND K), CAII (H AND K) LINES OF AN ACTIVE FILAMENT AT THE LIMB, WITH THE LPSP INSTRUMENT ABOARD THE OSO-8 SATELLITE

We scanned the H i Lα, Mg ii h and k, Ca ii K and H lines simultaneously with the LPSP instrument on OSO-8, to investigate the low and moderate temperature regions of an 'active region filament'. The Lα line is not reversed except for the innermost position in the prominence. Intensity (k/h), (K/H) ratios are respectively 2 and 1.1, indicating that the Mg ii lines are optically thin, and that Ca ii K is saturated, although not clearly reversed. The results obtained during the second sequence of observations (K saturated before Lα for example) indicate that within the size of the slit (1″ × 10″) we are not observing the same emitting features in the different lines. We also observe an important line-of-sight velocity at the outer edge of the feature, increasing outwards from a few km s-1 to 20 km s-1 within 2″. Less than half an hour later, this velocity is reduced to 15 km s-1 while the intensities increase. Full width at half maximum intensities for this component indicate turbulence variations from 22 to 30 km s-1. The observed high velocities at the top of the prominence can be compared with radial velocities that Mein (1977) observed in Hα at the edges of an active filament and interpreted as velocity loops slightly inclined on the axis of the filament. © 1979 D. Reidel Publishing Company.