Motions in a loop prominence

Motions of loop prominence knots have been studied on Hα-line filtergrams. By making use of contours of equal photographic density for entire cinegram it has been possible to significantly decrease the error in determining the locations of the knots. The method of mean velocities has been developed, which has permitted for the first time accurate determination of the laws of knot motion with sufficient accuracy. Two types of falling knots are distinguished: (1) those with a constant acceleration that is always below the gravitational acceleration, and (2) those with a constant velocity. The initial velocity of the falling knots is always different from zero. The gasdynamic theory has been developed to explain the deceleration of the two types of knots due to: the work done against the pressure force; pileup plasma raking; and shock-wave generation. The shock mechanism imparts a constant velocity to the motion. The temperature along the knot trajectories has been estimated. The ratio of the densities in the knots to the surrounding medium has been found. The aim of the present work is to gain new insight into the known observations of the motions in active prominences, in particular in the loop prominences, and to understand the reason for the observed motions. (orig.)