Geometric optics at lower hybrid frequencies

Abstract

Geometric optics is analyzed at lower hybrid frequencies using a realistic scaling of the cold plasma conductivity tensor. An explicit example displays the inadequacy of standard geometric optics in treating spatially varying plasmas. A new term is added to the ray Hamiltonian to remove this inconsistency. An adiabatic invariant, corresponding to the poloidal rotation of the ray, is introduced. The cold plasma waves can develop a singularity only at those points where the flux surface is tangent to upper and lower hybrid resonance surfaces, thus supporting the conjecture that heating occurs only at these points. The only other spatial points where singularities may develop in the geometric optics ray equations are the cyclotron resonances.