MHD Turbulence as a Foreground for CMB Studies

TL;DR

This paper demonstrates that MHD turbulence in the Galactic disk and halo can explain the observed power-law spectra of diffuse synchrotron emission and starlight polarization, impacting CMB foreground analysis.

Contribution

It models the effects of MHD turbulence on Galactic foregrounds, incorporating line-of-sight geometry and observational biases for better data fitting.

Findings

MHD turbulence explains synchrotron fluctuation spectra

Line-of-sight geometry is crucial for accurate modeling

Bias toward nearby stars affects polarization spectra

Abstract

Measurements of intensity and polarization of diffuse Galactic synchrotron emission as well as starlight polarization reveal power law spectra of fluctuations. We show that these fluctuations can arise from magnetohydrodynamic (MHD) turbulence in the Galactic disk and halo. To do so we take into account the converging geometry of lines of sight for the observations when the observer is within the turbulent volume. Assuming that the intensity of turbulence changes along the line of sight, we get a reasonable fit to the observed synchrotron data. As for the spectra of polarized starlight we get a good fit to the observations taking into account the fact that the observational sample is biased toward nearby stars.