Rotational models of solar prominences and flares

We assume the prominence (or flare) to be a rotating cylinder. For the two cases of the spin velocity being a constant and having a gradient, we calculate the profile of the Balmer lines and their variation from the centre of the prominence to the edge, and establish methods for finding the spin velocity from the inclination or shift of the lines and the velocity gradient from the curvature of the lines. These methods are then applied to the observed data of the ring flare of 1981 April 27.