Helios images of solar mass ejections

Abstract

The zodiacal light photometers on board the Helios B spacecraft are used to form images of solar mass ejection transients in the interplanetary medium. Several aspects of these data are unique: (1) They trace shapes of solar mass ejections observed near the solar surface in coronagraph images to distances at least as great as 0.5 AU using electron Thomson scattering. (2) When compared with earth‐based observations, the Helios data allow determination of the three‐dimensional shapes of the ejections. (3) The global viewpoint of the Helios spacecraft photometers allows imaging of mass ejections heading toward the spacecraft and then observations from within the ejection. Excess masses (above the ambient level) are determined for several ejections, and we find that they are generally comparable to or somewhat larger than masses obtained by coronagraph observations of ejections when they are closer to the sun.