Passage of radiation through inhomogeneous, moving media. XII. Polarized waves in a plane, sheared medium

Using the complete set of Maxwell equations, we follow the ray paths and Stokes parameters of a polarized wave which passes through a slab of differentially shearing material of variable refractive index. We relate the polarization state of the signal leaving the top of the slab to the polarization state of the initial wave. In general the two are not the same. We have done these calculations to illustrate the point that the polarization properties of observed pulsar signals may be very different from those of the emitted signals due to propagation effects in the differentially shearing magnetospheres that most pulsars are believed to possess. And while we recognize that the precise amount of polarization variation is model dependent, our calculations show that even for simple situations a noticeable polarization variation occurs. Accordingly the calculations reported here are an educative device: they show that it is, perhaps, unwise to assume that the observed polarization properties of pulsar signals are the same as the emitted signals.