DESTABILIZATION OF THE INTERNAL KINK BY ENERGETIC CIRCULATING IONS

A stability analysis is carried out for the m = 1, n = 1 internal kink mode, in the presence of energetic circulating particles. It is found that, including the effect of finite radial particle-orbit excursion, the m = 1 internal kink mode is strongly destabilized by the resonanc e interaction with the energetic passing particles. Such an instabilit y could explain the experimental observations of the ''fishbone'' osci llations during tangential neutral beam injection [W. W. Heidbrink et al., Phys. Rev. Lett. 57, 835 (1986)].