VISCOSITY EFFECT ON THE M = 1 INTERNAL LINK MODE IN A TOKAMAK

The role of ion viscosity in the m = 1 internal kink mode in a tokamak is discussed. It is explained that previous studies of this problem b ased on the slab approximation are non-adequate since they deal only w ith slab contribution of transverse viscosity and do not allow for bot h longitudinal (neoclassical) viscosity inherent in toroidal geometry and toroidal contribution of transverse viscosity. A small-amplitude o scillation equation in the singular layer allowing for all the above p arts of viscosity is given. It is shown that the slab contribution of the transverse viscosity can be ignored in the conditions of real toka mak devices since it proves to be small compared with the longitudinal viscosity. Excitation of the ideal mode due to the longitudinal visco sity in the banana regime is studied.