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In neutral beam injection and ion cyclotron resonance frequency (NBI+ICRF) heated high-temperature Joint European Torus (JET) plasmas, electron cyclotron emission (ECE) spectra measured by the Michelson interferometer are inconsistent with the electron bulk distribution being Maxwellian. This conclusion follows from new, accurate modeling of the ECE spectra over the full measured frequency range, covering the first four harmonics of the cyclotron frequency. A model distribution function obtained by fitting a measured ECE spectrum reveals a distortion of the Maxwellian that is sharply localized at ∼1.5×thermal momentum. A consequence deduced from this distribution is that the electron temperature measured by JET’s Thomson scattering diagnostic, which weighs the bulk electrons differently, should be lower than the ECE one in the spatial region where this distortion exists. This prediction appears to be confirmed by temperature profile comparisons showing that core Thomson scattering electron temperatures on JET are up to 20% lower than ECE values for plasmas with strong NBI+ICRF heating. The possibility of addressing experimentally the question of whether the plasma has a Maxwellian bulk is also discussed. This goal can be accomplished by observing the emission at different angles with respect to the magnetic field (oblique ECE). Simulations of oblique ECE spectra using the model distribution function obtained previously show an angular variation of the emission that is characteristic of the distorted bulk.

The ordinary mode damping near the electron‐cyclotron frequency is investigated using the relativistic dispersion relation. It is shown that the Doppler splitting of the absorption spectrum claimed by Arunasalam et al. [Phys. Rev. A 36, 3909 (1987); 37, 2063 (1988)] is an erroneous result obtained from an oversimplified dispersion relation and assuming an infinite speed of light in the resonance condition.

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.