Three-dimensional reconstruction of coronal mass ejections

Computer assisted tomography (CAT) techniques are used to reconstruct the three dimensional shape of coronal mass ejections in the interplanetary medium. Both the Helios 2 spacecraft zodiacal-light photometers and the Solwind coronograph measure changes in Thomson scattering of sunlight from electrons. The technique from near-perpendicular Solwind and Helios views are applied to determine the density of a mass ejection which left the solar surface on 24 May 1979. The coronograph and the Helios perspective views are not simultaneous; the Solwind observations extend outward to sky plane distances of only 10 of the solar radius, whereas the Helios 16 photometer observes to as close as 17 of the solar radius from the sun. The solution is obtained by assuming outward radial expansion and that the coronal mass ejections (CME's) have the same speed everywhere at the same height. The analyses show that CME's are extensive three dimensional structures (the CME of 24 May appears approximately shell) like in three dimensions.