Edge radial electric fields and their importance for confinement.

The paper reviews recent results pertaining to the phenomenology of the transition from L-mode to H-mode confinement and which reveal the role of the edge radial electric field. The mechanisms for electric field creation no reviewed and it is shown how they might affect plasma confinement and viscosity. The bifurcation phenomenon and the formation of the edge transport barrier are then explained within this theoretical framework. Special attention is also given to biasing experiments and their role in checking the theoretical models.