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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 He at the Meudon Solar tower and of the UVSP spectrometer on SMM in the C Iv 1548 ~ line show that cold and hot material had the same projection, although the upward Cw velocity structure was more extended than the He one. We present evidence that observed contrasts of the He absorbing structure can be interpreted in terms of a dynamic 'cloud model' overlying the chromosphere. He 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.

The question of the chromospheric features type III association is reconsidered by using Hc~ filtergrams both on and off band. A set of 44 metric type lII groups, for which an association can be ascertained with a high degree of confidence leads to the following results:(1) The type III's have a dual chromospheric association. Sometimes they are related to a flare, sometimes to a perturbation of a different kind. The latter is seen in absorption in the Hc~ core and 4-0.75 ~ away. It is interpreted as a rather dense and cool material in motion in the chromosphere or the low corona. A part of which moves downward, the other upward. The type III's are more closely related to the downward motion.(2) The type III associated absorbing features take place at the border of an active center and along an Hjl = 0 line. At the present time this appears as the most conspicuous property for marking them off from the great variety of the Hc~ absorbing features commonly observed on the Sun.(3) Most of the type II[ associated flares are related to an absorbing feature of the same kind, which appears before the flare itself. This indicates that the initial instability which is responsible for the type III emission is basically the same, whether the bursts are flare associated or not.Our observations give good evidence that an efficient acceleration of 10-100 keV electrons occur also in the absence of flares. Furthermore the chromospheric perturbation involved in this acceleration is, in many cases, clearly associated to the triggering of a flare. A tentative model is proposed. We assume that in relation with the Hc~ absorbing feature a stream of fast electrons is accelerated which in turn, under suitable conditions, triggers both the flare and the type II['s at the same time.

Simultaneous observations of radial velocities in a 'quiescent' prominence seen in Ha on the disk and in the underlaying photosphere have been obtained in the Meudon Observatory: Doppler shifts in photospheric lines are weaker than in the surrounding regions (<0.3 kms-1); the scale of velocity structures is smaller (< 10 4 kin). The vertical component of velocities cannot be neglected. Ha Doppler shifts show that: (a) Highest velocities are often correlated with high brightness horizontal gradients, which suggests that filament and surrounding bright regions belong to the same geometrical and dynamical structure. (b) Fast motions (7 km s -1) have short life-times (a few minutes). (c) Slow motions in dark regions (< 3 km s -1) are associated with blue shifts and may last several hours. This behaviour was confirmed in many other cases by filament observations with the 3-wavelength Ha patrol. This is consistent with EUV observations of the transition zone around prominences, but disagrees with 'downward motions' as seen at the limb, unless these motions do not refer to material velocities.