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  • E and B Polarizations from ...
    Brandenburg, Axel; Bracco, Andrea; Kahniashvili, Tina; Mandal, Sayan; Pol, Alberto Roper; Petrie, Gordon J. D.; Singh, Nishant K.

    The Astrophysical journal, 01/2019, Letnik: 870, Številka: 2
    Journal Article

    Gradient- and curl-type or E- and B-type polarizations have been routinely analyzed to study the physics contributing to the cosmic microwave background polarization and galactic foregrounds. They characterize the parity-even and parity-odd properties of the underlying physical mechanisms, such as, for example, hydromagnetic turbulence in the case of dust polarization. Here, we study spectral correlation functions characterizing the parity-even and parity-odd parts of linear polarization for homogeneous and inhomogeneous turbulence to show that only the inhomogeneous helical case can give rise to a parity-odd polarization signal. We also study nonhelical turbulence and suggest that a strong non-vanishing (here negative) skewness of the E polarization is responsible for an enhanced ratio of the EE to the BB (quadratic) correlation in both the helical and nonhelical cases. This could explain the enhanced EE/BB ratio observed recently for dust polarization. We close with a preliminary assessment of using the linear polarization of the Sun to characterize its helical turbulence without being subjected to the π ambiguity that magnetic inversion techniques have to address.