On the degree of circular polarization of synchrotron radiation

Formulas describing synchrotron radiation are extended to include the effect of the presence of an ambient medium and the effect of reabsorption and Faraday rotation on the degree of circular polarization. Results are: (1) The onset of Razin-Tsytovich suppression has no significant effect on the degree of circular polarization. (2) The onset of self-absorption in a source subject to weak Faraday rotation (negligible Faraday rotation in an absorption length) causes the degree of circular polarization to reverse its sign and to decrease (by between one half and one quarter for typical parameters) in magnitude. (3) As in (2) but for strong Faraday rotation (many rotations of the plane of polarization in an absorption length) the degree of circular polarization also reverses its sign and becomes slightly smaller in magnitude than for weak Faraday rotation.The transfer equation including the effects of the polarization is discussed in detail.