Spontaneous and driven perpendicular rotation in tokamaks

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Abstract
Recent theoretical work pertaining to spontaneously generated or forced plasma rotation in tokamaks is discussed. A description of the spontaneous poloidal spin‐up of tokamaks from the Stringer effect is given, highlighting the necessary condition of poloidally asymmetric particle accumulation. The possibility of inducing poloidal rotation using the Stringer effect by poloidally asymmetric particle fueling is suggested. The linear theory of E×B velocity shear stabilization of tokamak microinstabilities is discussed with an emphasis on the general features of the theory and some nonlinear concerns. It is argued that the critical velocity shear for stabilization of microinstabilities in tokamaks required by linear theory may be, in order of magnitude, a universal frequency. The feasibility of driving perpendicular rotation in tokamaks by neutral beam injection, to suppress microturbulence, is assessed for both toroidal and poloidal injection schemes.