Importance of radial electric fields for magnetically confined plasmas

The importance of radial electric fields in magnetic confinement devices is outlined. It has been demonstrated in limiter - and divertor tokamaks, helical devices and mirror machines with a variety of discharge - and heating conditions as well as edge biasing schemes that improved confinement is often associated with strongly radially varying profiles of $E_r$, and that $E \times B$ velocity shear turbulence stabilisation is a robust and universal mechanism which plays a major role in the formation and sustainment of transport barriers in magnetic confinement devices. Emphasis is put on the relation between the generation of electron internal transport barriers and the concept of profile consistency developed by Yu.N. Dnestrovskij, in which the plasma pressure and temperature profiles have a tendency to organize themselves into an "universal" profile shape, in agreement with the plasma minimum free energy principle.