Polarized radiative transfer, rotation measure fluctuations, and large-scale magnetic fields

On, Alvina Y. L. and Chan, Jennifer Y. H. and Wu Kinwah, Kinwah and Saxton, Curtis J. and Van Driel Gesztelyi, Lídia (2019) Polarized radiative transfer, rotation measure fluctuations, and large-scale magnetic fields. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 490 (2). pp. 1697-1713. ISSN 0035-8711

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Abstract

Faraday rotation measure (RM) at radio wavelengths is commonly used to scales on which magnetic fields vary in large-scale diffus astrophysical media can be inferred from correlations in the observe RM. RM is a variable which can be derived from the polarized radiativ transfer equations in restrictive conditions. This paper assesses th usage of rotation measure fluctuation (RMF) analyses for magnetic fiel diagnostics in the framework of polarized radiative transfer. We us models of various magnetic field configurations and electron densit distributions to show how density fluctuations could affect th correlation length of the magnetic fields inferred from the conventiona RMF analyses. We caution against interpretations of RMF analyses when distributed and fractal-like density structures. As the spatia correlations are generally not the same in the line-of-sigh longitudinal direction and the sky plane direction, one also needs t clarify the context of RMF when inferring from observational data. I complex situations, a covariant polarized radiative transfer calculatio is essential to capture all aspects of radiative and transpor processes, which would otherwise ambiguate the interpretations o magnetism in galaxy clusters and larger scale cosmological structures

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