Magnetohydrodynamic mechanisms of electric-field transport suppression and plasma-rotation generation, with special reference to tokamak's reversed-shear confinement

A magnetohydrodynamic analysis is made of the mechanisms of electric-field transport suppression and plasma-flow generation in the context of tokamak's reversed-shear (RS) confinement. The turbulent transport of heat is shown to be suppressed through the combined effect of radial electric field and charge inhomogeneity. The similarity is pointed out between the internal transport barrier in RS modes and the edge counterpart in high-confinement modes. A concave electric-current profile is shown to be a cause of the global plasma rotation, and the latter contributes to the occurrence of a negative radial electric field that plays a key role in the former suppression mechanism.