Relaxation of plasma toroidal rotation in tokamaks and anomalous viscosity

A theory of anomalous viscosity in tokamaks is presented. Previous results are generalized for the case Mβ/m > or approx. 1, where M and m are the ion and electron masses, respectively, and β is the ratio of the plasma pressure to the magnetic pressure. A complete set of equations for anomalous transport with gradients of density, temperature and toroidal momentum is obtained. This theory describes the damping of the toroidal rotation after neutral beam injection has been switched off. A comparison of theoretical and experimental results is presented and good agreement is observed. In addition, the contribution of drift waves with wavelengths comparable to the ion Larmor radius is analysed, and model equations for the toroidal and poloidal velocities, including parallel neoclassical viscosity and two types of anomalous viscosity, are obtained. (author). 14 refs, 1 fig