JOINT NANCAY RADIOHELIOGRAPH AND LASCO OBSERVATIONS OF CORONAL MASS EJECTIONS - I - THE 1 JULY 1996 EVENT

The development of a coronal mass ejection on 1 July 1996 has been ana lyzed by comparing the observations of the LASCO/SOHO coronagraph with those of the Nancay radioheliograph. This comparison brings new insig ht and very useful diagnosis for the study of CME events. It is shown that the initial instability took place in a small volume located abov e an active region and that the occurrence of short radio type III bur sts implies a triggering process due to magnetic held interactions. Th e subsequent spatial and temporal evolution of the radio emission stro ngly suggests that the large scale structure becomes unstable within t he first minute of the event.