Circular Polarization of Thermal Radiation in a Magnetic Field

Abstract

It is argued that light emission of electronic origin from any thermal source in a magnetic field is characterized by a spectrally diffuse circular polarization along the B field, even when the emission is devoid of spectral structure, i.e., is blackbody-like. A model "gray-body" radiating system in a B field is shown to emit with a fractional circular polarization given to first order in B by q( ) - (eB/?n)/co, where", is the optical frequency. For B = 10 gauss, q 10- at visible wavelengths. The polarization is right-handed for B along the light k-vector. The effect has implications for the detection of magnetic fields in condensed stars (such as white dwarfs) and other stellar objects, and also for plasma and solidstate physics. Results of a preliminary laboratory ezperiment, which has verified the reality of the effect, are also summarized.