Transport of rf Energy to the Lower Hybrid Resonance in an Inhomogeneous Plasma

Localized coupling structures, such as open-ended wave guides located close to the plasma boundary, radiate a spectrum of electrostatic waves that are accessible to the lower hybrid layer in an inhomogeneous plasma. The energy flow is confined within narrow channels, similar to the resonance cone effect discussed by Fisher and Gould. Radical changes in the energy-flow picture result if the constant-density contours are aligned at a small angle [$\ensuremath{\sim}{(\frac{{m}_{e}}{{m}_{i}})}^{\frac{1}{2}}$] to the magnetic field.