Evolution of complex amplitudes ratio in weakly anisotropic plasma

Abstract

AbstractThe equation for evolution of the complex amplitudes ratio (CAR) ζ = Ey/Ex in weakly anisotropic inhomogeneous media is derived on the basis of quasi-isotropic approximation (QIA) of the geometrical optics method. This equation is convenient for the description of electromagnetic wave polarization in magnetized plasma of thermonuclear reactors like the ITER. The equation for the CAR is in agreement with other approaches, analyzing polarization evolution in weakly anisotropic media, in particular, with the equation for complex polarization angle and, via QIA equations, with the Segre equation for Stokes vector evolution. Simple analytical solutions for the CAR, which relates to normal mode propagation in homogeneous and weakly inhomogeneous plasma, are obtained. Besides, the equation for the CAR is solved numerically to describe the phenomenon of normal wave conversion in magnetized plasma in the vicinity of the orthogonality point between the ray and the static magnetic field. In distinction to the line-averaged measurements in traditional plasma polarimetry, the phenomenon of normal wave conversion opens the way for measuring the local plasma parameters near the orthogonality point.