Solar and interplanetary observations of the mass ejection on 7 May, 1979

Abstract

We present observations of a mass ejection that was observed by five different instruments along its way from the solar surface to more than 100 solar radii. The instruments involved are the ground-based Hα coronagraph at Wroclaw, the white-light SOLWIND coronagraph on board the P78-1 satellite, zodiacal light photometers of the HELIOS B spacecraft, in situ plasma detectors and magnetometers on board the HELIOS B spacecraft, and interplanetary scintillation measurements on the ground. By using a CAT-scan analysis of the images obtained by the SOLWIND coronagraph near the Earth and HELIOS B photometers placed at 0.3 AU perpendicular to the Earth-Sun line, we have been able to get a three-dimensional density reconstruction of the mass ejection and fit the best velocity curve for its propagation. Although problems exist in smoothly joining the height-time curves (for instance, we had to reduce the brightness of the SOLWIND data by more than a factor of two to make the data sets agree photometrically), both this analysis and direct measurements by the other experiments clearly indicate higher speeds at greater distances from the Sun. The plasma acceleration in this case was obviously not limited only to distances within 3 R 0 , as is usually the case, but continued beyond the outer limit of the coronagraph view at ∼ 8 R 0 .