Abstract
During a coordinated SMY program, the consecutive formation of two new active centers merging together within AR 2646 was observed from 28 August, to 5 September, 1980. The two preceding spots compressed an inverse polarity spot on 1 September 1980, causing recurrent ejecta of matter with time intervals around 10 min. The observations of the MSDP spectrograph operating in Hα at the Meudon Solar tower and of the UVSP spectrometer on SMM in the Civ 1548 A line show that cold and hot material had the same projection, although the upward Civ velocity structure was more extended than the Hα one. We present evidence that observed contrasts of the Hα absorbing structure can be interpreted in terms of a dynamic ‘cloud model’ overlying the chromosphere. Hα matter follows a magnetic channel with upward velocity around 20–30 km s−1 in the first phase of the event and with downward velocity (∼ - 40 km s−1) in the second phase. The stored energy is not sufficient to trigger a flare, nor even to propulse matter along the full length of an arch, because of the periodic reorganisation of the magnetic field.
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