The loop prominence of 11 August 1972: A coronal continuum event

Abstract

Observations of a loop prominence formed after the flare of 11 August 1972 are discussed. Estimates of electron density are obtained from (a) the line ratio of the Ca xv forbidden lines and (b) a Thompson scattering model. Both methods give an approximate value of ne = 1011 cm-3. This density was high enough to render the loop structures visible as continuum features, corresponding to the Ca xv structures as seen in the plane of the sky. By a double exposure technique, it was found that the loop structures seen in Hα and Fe xiv differ significantly.