Propagation of electrostatic electron cyclotron waves at oblique angles

The results of a theoretical and numerical analysis of the dispersion relation for electrostatic modes with frequencies around the electron cyclotron frequency, ωsub(c), at quasi-perpendicular propagation are presented and discussed in view of the mode conversion of the extraordinary mode into Bernstein modes. It is found that the mode conversion depends very sensitively on the direction of propagation, a slight deviation from perpendicular propagation being sufficient to strongly modify the theoretical predictions obtained for propagation at 900. This finding is discussed in connection with the application to plasma heating. Quasi-perpendicular propagation around 2ωsub(c) is also considered and the numerical solution of the corresponding electrostatic dispersion relation is presented and discussed. (author)