Dust polarization and interstellar turbulence

Marc Kamionkowski (Johns Hopkins)

September 23, 2016

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Abstract: Perhaps the most surprising result from the Planck satellite is the observation that the E-mode power in the dust polarization is twice that in the B mode, in stark contrast to pre-Planck expectations of roughly equal dust powers in E and B modes. I will show how the E- and B-mode powers are determined by fluctuations in the interstellar medium. I will argue that the observed E/B ratio, as well as the TE (temperature-polarization) cross-correlation (which is observed to be positive) are not easily reconciled with those expected in the MHD-turbulence models usually invoked to account for the fluctuations. I will suggest that the scales probed by Planck may overlap the outer scale for interstellar turbulence and discuss a simple phenomenological model. I will then outline some interesting directions for future related research.