KINEMATICS OF A LOOP PROMINENCE

The kinematics of a loop system has been studied from high resolution Ca ii K line spectra and Hα filtergrams recorded at Oslo Solar Observatory. Emission features are seen to fall at supersonic velocities from the top of the arches towards the chromosphere. Our data are in agreement with the assumption of matter falling freely along a dipole type magnetic field of maximum height 100-150 thousand km. There is a slight asymmetry between positive and negative line shifts which can be accounted for as a tilt of the individual loops relative to the plane of the sky of 5-10°. The planes of the loops are also inclined by a small angle of approximately 15°. It appears that matter starts from rest at the top of the loops. An observed tilt of some emission features in the K line spectra may be explained by a gradient in the line-of-sight velocity with height caused by the curvature of the dipole type loops. © 1979 D. Reidel Publishing Co.