Coronal mass ejections: Structure and dynamics

We discuss in this paper some issues related to the relationship, currently thought to be relatively strong, between large scale solar eruptive events and twisted magnetic flux ropes (TFRs). We first consider the possibility to prove the presence of a TFR in a pre-eruptive configuration by using a model along with observational information provided by a vector magnetograph. Thus we examine, in the framework of a generic model in which the coronal field is driven into an evolution by changes imposed at the photospheric level, several mechanisms which may lead to the formation and the disruption of a TFR. We consider in particular the development of a MHD instability, and we address the issues of the energy and helicity contents of an erupting configuration.