Generation of superthermal electrons interacting with waves in lower-hybrid range of frequency revisited

The problem of quasilinear diffusion of plasma electrons, resonantly interacting with waves in lower-hybrid range of frequency launched from the exterior, is examined within a self-consistent one-dimensional homogeneous model. An analytical solution is obtained, which allows the derivation of a simple formula for the plasma current in terms of the parameters characterizing the spectral distribution of the r.f. power source. The major outcome is a dramatic sensitivity of the plasma current to the presence of a small, high-Nsub(parallel) component in the r.f. power source spectral distribution, in agreement with previous numerical calculations. (author)