Evolution of polarization for radiation crossing a plasma layer of quasi-transverse propagation and the interpretation of radioastronomical measurements

First the complete change of polarization is obtained for radiation crossing a layer of quasi-transverse propagation in a plasma where the longitudinal component of the magnetic field changes signs along the propagation direction, while the transverse component is different from zero. The analysis is made for arbitrary input polarization. The results are then used for the interpretation of previously published measurements of radio emission from solar active regions. It is found that if a sufficiently narrow detection bandwidth is used, more information can be obtained from measurements than has been considered up to now. The present analysis is also of interest for other astrophysics problems.