Time evolution of electron cyclotron absorption during lower hybrid current generation in tokamak plasmas

The time evolution of the electron distribution function in a magnetized plasma under the action of externally launched lower hybrid waves, is studied by means of quasi-linear theory. The lower hybrid spectra given by a model that shows explicit dependence on the electron temperature, the electron density, and the ambient magnetic field. The time-dependent distribution function obtained is then utilized in order to follow the time evolution of the absorption coefficient of electron cyclotron waves by the tail of the distribution function, for the ordinary mode in perpendicular propagation, and for the extraordinary mode in oblique propagation. (author). 12 refs, 5 figs