Studying Magnetohydrodynamic Turbulence with Synchrotron Polarization Dispersion

Jian-Fu Zhang; Alex Lazarian; Hyeseung Lee; Jungyeon Cho

doi:10.3847/0004-637X/825/2/154

paper

Studying Magnetohydrodynamic Turbulence with Synchrotron Polarization Dispersion

arXiv:1605.01307 · doi:10.3847/0004-637X/825/2/154

Abstract

We test a new technique of studying magnetohydrodynamic (MHD) turbulence suggested by Lazarian \& Pogosyan, using synthetic synchrotron polarization observations. This paper focuses on a one-point statistics, which is termed the polarization frequency analysis, that is characterized by the variance of polarized emission as a function of the square of wavelengths along a single line of sight. We adopt a ratio $η$ of the standard deviation of the line-of-sight turbulent magnetic field to the line-of-sight mean magnetic field to depict the level of turbulence. When this ratio is either large ( $η ≫ 1$ ), which characterizes a turbulent field dominated region, or small ( $η ≲ 0.2$ ), which characterizes a mean field dominated region, we obtain the polarization variance $⟨ P^{2} ⟩ \propto λ^{- 2}$ and $⟨ P^{2} ⟩ \propto λ^{- 2 - 2 m}$ , respectively. At small $η$ , i.e., the mean field dominated region, we successfully recover the turbulent spectral index by the polarization variance. We find that our simulations agree well with the theoretical prediction of Lazarian \& Pogosyan. With existing and upcoming data cubes from the Low-Frequency Array for Radio astronomy (LOFAR) and Square Kilometer Array (SKA), this new technique can be applied to study the magnetic turbulence in the Milky Way and other galaxies.

31 pages, 18 figures, Accepted for publication in the Astrophysical Journal

Studying Magnetohydrodynamic Turbulence with Synchrotron Polarization Dispersion

Abstract

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