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The combined effects of the dc electric field and electron‐cyclotron wave absorption in tokamak plasmas are investigated. The case of the ordinary mode for nearly normal propagation from the low magnetic field side is studied by a two‐dimensional Fokker–Planck code. It is found that the small fraction of the wave energy that goes into the superthermal electrons enhances the effect of the continuous pushing of the tokamak electric field.

The general properties of electron cyclotron radiation emitted by the current‐carrying superthermal tail in tokamak plasmas are investigated. Two situations are considered, namely, the case of an extended tail as it occurs in present‐day experiments and that in which the velocity range of the tail is much less than its mean speed. For the former case, we show that most of the emitted radiation obeys Kirchhoff’s law. In the latter case, which is suited for reactor‐like parameters, a simple relation is obtained between the tail momentum distribution and the radiation temperature.

Wave absorption near the electron cyclotron gyrofrequency by the current‐carrying energetic tail in tokamak plasmas is investigated. It is shown that by the proper choice of the angle of propagation, strong wave damping occurs for wave frequencies much less than the central electron cyclotron frequency and that the extraordinary mode can be launched from the low magnetic field side of the torus. It is also found that wave absorption is weakly dependent on the perpendicular temperature of the resonant particles.

The perpendicular propagation of the extraordinary wave near the second electron cyclotron harmonic is analyzed by means of a numerical code embodying a full wave relativistic scheme. Discussion of the results in comparison with the standard WKB ones is performed in view of absorption and emission applications. It is found that in the density regime called the ’’overcritical case’’ the effective optical depth scales, as an effect of the increased interaction of the extraordinary wave with a quasielectrostatic wave, differently from the WKB estimate. An explicit evaluation of reflection and transmission coefficients is given.

Emission and absorption of electron cyclotron radiation in a tokamak plasma in the presence of a fast‐electron tail is investigated. Specifically, the case in which the perpendicular temperature of the very end of the tail has a sharp rise is discussed. This situation occurs during rf current drive, and wave emission and transmission measurements may yield accurate information on the tail formation. The theory is developed for propagation in a homogeneous magnetic field and applies to the vertical direction of the tokamak. The quasilinear theory of wave absorption is also investigated. This study is motivated by the possibility of remote control of temperature anisotropy instability by electron cyclotron heating. The case of the extraordinary mode propagating from the low‐magnetic‐field side of the torus in the equatorial plane is numerically discussed.

The theory of current drive by the combined effects of lower‐hybrid and electron‐cyclotron wave absorption is investigated. The case of a spatially homogeneous lower‐hybrid diffusion coefficient and the electron ordinary mode propagating nearly normal to the magnetic field is considered. The effect of selective electron‐cyclotron wave absorption for optimizing lower‐hybrid current drive is discussed for two situations, namely, the wave frequency close to or much less than the electron‐cyclotron gyrofrequency, which corresponds to particle heating for moderate velocities and mildly relativistic energies, respectively. In the former case, by using the numerical solution of the Fokker–Planck equation it is shown that electron heating is suited for controlling the density of the current‐carrying tail. The latter case is investigated for moderate wave powers and is shown to be most appropriate for optimizing the ratio J/P.

The power dependence of the wave damping in a tokamak plasma for arbitrary direction of propagation, mode of polarization, and wave frequency is investigated. Using a 2‐D Fokker–Planck code, it is shown that the wave damping increases or decreases with the rf power depending on the velocity range of the absorbing electrons.

Electron‐cyclotron resonance absorption for oblique propagation at frequency significantly below the central electron gyrofrequency is considered. It is shown that the extraordinary mode for external launching is suited for additional heating in a tokamak reactor. The properties of wave damping at downshifted frequencies are discussed and are found to differ from those at f≊fc. Using the ray‐tracing code, the wave damping of the e mode is investigated at high densities for which strong refraction of the wave beam occurs.