Simultaneous monochromatic and spectral observations of two large loop prominence groups

Using the solar tower telescope of Nanjing University, we observed the two large loop prominence groups of 1982 Dec. 20 and 1983 Feb. 9. Hα photographs and spectra around the Hα and H and K lines were obtained simultaneously. From these data, we derived a line of sight velocity distribution, which agrees perfectly with the distribution for matter falling freely without viscosity. From the widths of the Hα and the K lines, we found the loop material to have a uniform kinetic temperature and a turbulent velocity that increases with height. From the central intensities of the lines we derived a density of n( H) ≅ 1.3 − 2.6 × 10 10 cm −3. A possible mechanism of the formation of loop prominence groups and their relation with flares are discussed.