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Depolarization canals and interstellar turbulence

Lookup NU author(s): Dr Andrew Fletcher, Professor Anvar ShukurovORCiD


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Recent radio polarization observations have revealed a plethora of unexpected features in the polarized Galactic radio background that arise from propagation effects in the random (turbulent) interstellar medium. The canals are especially striking among them, a random network of very dark, narrow regions clearly visible in many directions against a bright polarized Galactic synchrotron background. There are no obvious physical structures in the ISM that may have caused the canals, and so they have been called Faraday ghosts. They evidently carry information about interstellar turbulence but only now is it becoming clear how this information can be extracted. Two theories for the origin of the canals have been proposed; both attribute the canals to Faraday rotation, but one invokes strong gradients in Faraday rotation in the sky plane (specifically, in a foreground Faraday screen) and the other only relies on line-of-sight effects (differential Faraday rotation). In this review we discuss the physical nature of the canals and how they can be used to explore statistical properties of interstellar turbulence. This opens studies of magnetized interstellar turbulence to new methods of analysis, such as contour statistics and related techniques of computational geometry and topology. In particular, we can hope to measure such elusive quantities as the Taylor microscale and the effective magnetic Reynolds number of interstellar MHD turbulence. © EAS EDP Sciences 2007.

Publication metadata

Author(s): Fletcher A, Shukurov A

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: Sky Polarisation at Far-Infrared to Radio Wavelengths: The Galactic Screen Before the Cosmic Microwave Background

Year of Conference: 2007

Pages: 109-128

ISSN: 1638-1963

Publisher: EDP Sciences


DOI: 10.1051/eas:2007008

Library holdings: Search Newcastle University Library for this item

ISBN: 9782868839800