Boundary effects and the circular polarization of synchrotron sources.

The paper discusses, in a semiquantitative way, the effect of the boundary of a synchrotron source on the conversion of linear into circular polarization. It is found that a boundary layer does not affect the expected degree of circular polarization due to ellipticity of the modes provided that the ellipticity is small and that the modes get out of phase substantially either inside the source or in the boundary layer. The absence of Faraday depolarization implies little Faraday rotation inside the source, and the lack of variation of position angle with frequency implies little Faraday rotation either inside the source or in the boundary layer.