Recovering 3D Magnetic Turbulence from Single-Frequency Faraday Screens

TL;DR

This paper presents a method to recover turbulence statistics in magnetic fields by analyzing the spectrum of polarization directions from single-frequency synchrotron radiation passing through a turbulent Faraday screen, supported by simulations and analytical models.

Contribution

It introduces a new diagnostic using the spectrum of polarization directions to distinguish turbulence properties in emission and Faraday screens, validated by simulations and theory.

Findings

SPD is more sensitive to Faraday screen turbulence.

A criterion to identify the sampled turbulence region.

Practical approach for turbulence analysis in radio polarimetry.

Abstract

Statistics of polarized synchrotron radiation carry information about the properties of the underlying turbulence. Different statistical measures constructed from observables probe turbulence properties in different ways. We consider a setup in which synchrotron radiation is emitted in a distant volume and then passes through a turbulent screen that induces Faraday rotation. Using both MHD simulations and synthetic turbulence spectra, we explore the spectrum of observed polarization directions measured at a single frequency as a diagnostic for recovering the statistics of turbulence in both the emitting region and the Faraday-rotation screen. We compare these results with our analytical expectations. We also compare the spectrum of polarization direction (SPD) with the wavelength-derivative diagnostic introduced and analytically explored by Lazarian \& Pogosyan. We demonstrate that the SPD exhibits greater sensitivity to turbulence in the Faraday screen. We provide an observer-friendly criterion to determine whether the SPD samples turbulence in the synchrotron-emitting region or in the Faraday screen. These results open a practical pathway for extracting turbulence statistics from existing and forthcoming single-band radio polarimetry.