AAS 205th Meeting, 9-13 January 2005
Session 74 ISM II
Oral, Tuesday, January 11, 2005, 10:00-11:30am, California

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[74.02] Circular Polarization From Tangled Magnetic Field

A. E. Broderick (ITC, Harvard College Observatory), R. D. Blandford (KIPAC)

Radiative transfer effects through magnetized plasmas plays a central role in the polarimetric properties of many astrophysical sources. Until recently, Faraday rotation and conversion were the primary effects considered. However, in nonuniform environments, geometric phase effects can also occur. We find that it is possible to produce a circular polarization fraction which increases with frequency, until reaching a high frequency cutoff, accompanied by a neglible linear polarization. This mechanism requires only a net magnetic helicity (though not a net field), and hence may be associated with disk angular momentum in accreting environments. We apply this mechanism to radio observations of circular polarisation in AGN, and in particular the Galactic center, finding that it is capable of explaining their observed polarimetric properties. In addition, we consider an application to high mass X-ray binaries and predict the possibility of significant degrees of circular polarization in these systems in the infrared.

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© 2004. The American Astronomical Society.