Abstract
We study the effect of a background of microturbulence generated by unstable short scale length electron temperature gradient (ETG) modes on the excitation and nonlinear evolution of neoclassical tearing modes (NTMs) in a tokamak. A self-consistent model calculation is carried out in which low frequency stresses generated by the ETG modes act on the NTM and which in turn acts back on the ETG evolution by modulating the turbulence profile. The principal physical consequences of the ETG turbulence are to create an anomalous current diffusivity and an anomalous resistivity contribution. These turbulent transport contributions are incorporated in the evolution equations of a single helicity NTM to obtain a generalized Rutherford equation, and their impact on the instability threshold and growth rate is discussed.
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