Lower-hybrid wave propagation in toroidal plasmas

The electrostatic lower-hybrid wave equation is solved in toroidal geometry by expanding the wave potential as a sum of poloidal eigenmodes and calculating their mutual coupling to first order in ε=r/R. The resulting solutions are compared to toroidal ray tracing calculations. These solutions present a technique that can explicitly determine the evolution of the wave poloidal mode number spectrum over long trajectories that involve multiple passes of the plasma column.