Magnetic flux ropes: Fundamental structures for eruptive phenomena

We consider some general aspects of twisted magnetic flux ropes (TFR), which are thought to play a, fundamental role in the structure and dynamics of large scale eruptive events. We first discuss the possibility to show the presence of a TFR in a pre-eruptive configuration by using a model along with observational informations provided by a vector magnetograph. Then we present, 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, including the development of a MHD instability, and we discuss the issues of the energy and helicity contents of an erupting configuration. Finally we report sonic results of a recent, and more ambitious approach to the physics of TFRs in which one tries to describe ill a consistent way their rising through the convection zone, their emergence through the photosphere, and their subsequent, evolution in the corona.