Local analyses of mode conversion at S=n_z² resonances in the ion cyclotron range of frequencies: Letter to the editor

For the S=n_z² resonances in the ion cyclotron heating of Tokamak plasmas a simple formula is derived which relates the converted fast wave power flux to the local dielectric tensor elements ε_xx, ε_xy and to the fast wave electric field at the resonance. Here S= ε_xx, and n_z denotes the parallel refractive index of the radiation along the background magnetic field. The validity of this estimate is analyzed for finite electron inertia and finite temperature and its usefulness in predicting the conversion at the edge plasma resonances is shown.