Faraday depolarization and induced circular polarization by multipath propagation with application to FRBs

Paz Beniamini, Pawan Kumar, Ramesh Narayan

Research output: Contribution to journalArticlepeer-review


We describe how the observed polarization properties of an astronomical object are related to its intrinsic polarization properties and the finite temporal and spectral resolutions of the observing device. Moreover, we discuss the effect that a scattering screen, with non-zero magnetic field, between the source and observer has on the observed polarization properties. We show that the polarization properties are determined by the ratio of observing bandwidth and coherence bandwidth of the scattering screen and the ratio of temporal resolution of the instrument and the variability time of screen, as long as the length over which the Faraday rotation induced by the screen changes by ∼πis smaller than the size of the screen visible to the observer. We describe the conditions under which a source that is 100 per cent linearly polarized intrinsically might be observed as partially depolarized, and how the source's temporal variability can be distinguished from the temporal variability induced by the scattering screen. In general, linearly polarized waves passing through a magnetized scattering screen can develop a significant circular polarization. We apply the work to the observed polarization properties of a few fast radio bursts (FRBs), and outline potential applications to pulsars.

Original languageEnglish
Pages (from-to)4654-4668
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - 1 Mar 2022

Bibliographical note

Publisher Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.


  • ISM: structure
  • Polarization


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