Coupled-Mode Propagation in an Inhomogeneous Plasma in the Presence of Shear

An experiment is discussed in which an electromagnetic wave polarized in the extraordinary mode is propagated through a plasma confined by a magnetic field having a weak shear, which results in creation of an ordinary wave component. Resonant and nonresonant conditions of propagation are explored for the incident extraordinary wave. The transmitted power in the extraordinary and ordinary modes is measured as a function of magnetic field for constant plasma density. Theoretical results obtained numerically from the coupled second-order equations describing propagation in a weakly inhomogeneous plasma with shear are found to be in substantial agreement with the experimental results. Relevance of this work to the spatial determination of the poloidal magnetic field in tokamaks is suggested.