Electron cyclotron interaction in the lower hybrid heating regime

The analysis of the down shifted resonant interaction of electron cyclotron waves in a Tokamak, operating in the lower hybrid heating regime, has been performed by a numerical computation of the ray trajectories, the local relativistic power absorption and the driven current density profile. Top and equatorial launch have been considered. The conditions for localized power deposition and efficient current drive, suitable for current density profile modifications, have been investigated in terms of the injection and plasma parameters. The physical interpretation of the results has been given through the analysis of the electron resonance with both LH and EC waves in momentum space, of the corresponding spatial resonant regions and of the refractive effects. The results are applied to the injection of EC waves at 140 GHz in FTU.