Linear and quasilinear theory of electron cyclotron wave resonance heating in tokamak plasmas

Linear and quasilinear theory of wave absorption for the ordinary mode near the electron cyclotron frequency is investigated. A simple physical derivation of the wave damping and the quasilinear equation is presented. The special case of quasiperpendicular propagation in a tokamak plasma is numerically discussed using a two dimensional initial value code to investigate the distortion of the electron momentum distribution from an initial Maxwellian. Wave damping and power deposition are obtained for several values of the wave power and half-width of the wave-packet. It is shown that for powers of interest for electron heating Coulomb collisions are not sufficient to avoid quasilinear flattening of the electron distribution and, consequently, a reduction of the heating rate as compared to the linear case. (author). 2 refs, 7 figs