VISHNIAC-TYPE CONTRIBUTION TO THE POLARIZATION OF THE CMBR - ART. NO.063002

Radiation which has a quadrupole component of anisotropy can get polar ized by Thomson scattering from charged particles. In the cosmological context, the microwave background photons develop significant quad ru pole anisotropy as they free stream away from the epoch of standard re combination. Reionization in the post recombination era can provide fr ee electrons to Thomson scatter the incident anisotropic cosmic microw ave background radiation photons. We compute the resulting polarizatio n anisotropy on small (arc minute) angular scales. We look for signifi cant nonlinear contributions, as in the case of the Vishniac effect in temperature anisotropy, due to the coupling of small-scale electron d ensity fluctuations, at the new last scattering surface, and the tempe rature quadrupole. We show that while in cold dark matter type models this does not lead to very significant signals (similar to 0.02-0.04 m u K) a larger small angular scale polarization anisotropy, (similar to 0.1-0.5 mu K) can result in isocurvature-type models. [S0556-2821(98) 07616-4].