Rotation-transport threshold model of neoclassical tearing modes

A rotation-tran sport threshold model of neoclassical tearing modes (NTMs) is suggested. It is assumed that weakening of the bootstrap current effect is determined by competition of perpendicular transport and island rotation, which is in contrast to the known transport threshold models dealing with the parallel transport or parallel convection instead of island rotation. It is shown that for sufficiently strong island rotation the perpendicular transport does not lead to decreasing the bootstrap current contribution into the island width evolution equation. It is explained that the island rotation can prevail over the parallel transport/convection mainly for the case of ion contribution into the bootstrap current effect. Interrelation between the rotation-tran sport threshold model and the known ones is discussed. A generalized transport threshold model of NTMs describing the competition of the perpendicular transport with the island rotation, parallel transport and parallel convection is formulated. It is shown that the perpendicular transport can lead to weakening the bootstrap drive contribution only if it overpowers all the competitive effects.