Cosmic Microwave Background Polarization Signals from Tangled Magnetic Fields

Abstract

Tangled, primordial cosmic magnetic fields create small rotational velocity perturbations on the last scattering surface (LSS) of the cosmic microwave background radiation (CMBR). For fields which redshift to a present value of $B_0 = 3\times 10^{-9}$ Gauss, these vector modes are shown to generate polarization anisotropies of order $0.1\mu K - 4 \mu K$ on small angular scales ($500 < l < 2000$), assuming delta function or a power law spectra with $n=-1$. About 200 times larger signals result for $n=2$ spectra. Unlike inflation generated, scalar modes, these signals are dominated by the odd parity, B-type polarization, which could help in their detection.Comment: 4 pages, Revtex, matches version to be published in Phys. Rev. Let