Recent experimental results on the DIII-D tokamak have demonstrated that with off-axis electron-cyclotron heating (ECH) there is a large inward electron heat flux up the temperature gradient. We propose that owing to the finite drift parameter for the toroidal current, enhanced by the presence of trapped electrons, the isotropic component of the distribution function is driven non-Maxwellian. The enhanced number of energetic electrons leads to an extra and nonlinear inward heat flux in quantitative agreement with experiment. Furthermore, this model permits an understanding of profile consistency or resilience in tokamaks.
Electron cyclotron emission during electron cyclotron heating in tokamaks