Neoclassical internal kink modes in a tokamak

The basic part of previous theoretical works on the internal kink modes in a tokamak, simulated by experimental observations of saw-tooth oscillations and fishbone, gives an inadequate description of these observations, because a neoclassical banana mode is realized in the experiments, and the part of works noted has been realized with neglect to neoclassical effects. When realizing resistive modes the basic attention is paid to the drift tearing mode with the frequency close to the electron drift one. It is shown that its increment depends notably on the increment depends notably on the neoclassical resistive viscosity effect. It is underlined that electron viscosity leads to a magnetic hill type effect. 54 refs