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Faraday Rotation of the Cosmic Microwave Background Polarization by a Stochastic Magnetic Field

Arthur Kosowsky·Tina Kahniashvili·George Lavrelashvili·Bharat Ratra
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Abstract

A primordial cosmological magnetic field induces Faraday rotation of the cosmic microwave background polarization. This rotation produces a curl-type polarization component even when the unrotated polarization possesses only gradient-type polarization, as expected from scalar density perturbations. We compute the angular power spectrum of curl-type polarization arising from small Faraday rotation due to a weak stochastic primordial magnetic field with a power-law power spectrum. The induced polarization power spectrum peaks at arcminute angular scales. Faraday rotation is one of the few cosmological sources of curl-type polarization, along with primordial tensor perturbations, gravitational lensing, and the vector and tensor perturbations induced by magnetic fields; the Faraday rotation signal peaks on significantly smaller angular scales than any of these, with a power spectrum amplitude which can be comparable to that from gravitational lensing. Prospects for detection are briefly discussed.

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Arthur Kosowsky, Tina Kahniashvili, George Lavrelashvili, Bharat Ratra. 2005-03-24. Faraday Rotation of the Cosmic Microwave Background Polarization by a Stochastic Magnetic Field. https://doi.org/10.1103/physrevd.71.043006

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