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FARADAY ROTATION: EFFECT OF MAGNETIC FIELD REVERSALS

Abstract

The standard formula for the rotation measure (RM), which determines the position angle, {psi} = RM{lambda}{sup 2}, due to Faraday rotation, includes contributions only from the portions of the ray path where the natural modes of the plasma are circularly polarized. In small regions of the ray path where the projection of the magnetic field on the ray path reverses sign (called QT regions) the modes are nearly linearly polarized. The neglect of QT regions in estimating RM is not well justified at frequencies below a transition frequency where mode coupling changes from strong to weak. By integrating the polarization transfer equation across a QT region in the latter limit, I estimate the additional contribution {Delta}{psi} needed to correct this omission. In contrast with a result proposed by Broderick and Blandford, {Delta}{psi} is small and probably unobservable. I identify a new source of circular polarization, due to mode coupling in an asymmetric QT region. I also identify a new circular-polarization-dependent correction to the dispersion measure at low frequencies.
Authors:
Melrose, D B [1] 
  1. SIfA, School of Physics, University of Sydney, NSW 2006 (Australia)
Publication Date:
Dec 20, 2010
Product Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 725; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/725/2/1600
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; FARADAY EFFECT; MAGNETIC FIELD REVERSAL; POLARIZATION; RADIANT HEAT TRANSFER; ENERGY TRANSFER; HEAT TRANSFER; MAGNETIC FIELD CONFIGURATIONS; PHYSICS
OSTI ID:
21476697
Country of Origin:
United States
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 0004-637X; ASJOAB; TRN: US10P9198070140
Availability:
Available from http://dx.doi.org/10.1088/0004-637X/725/2/1600
Submitting Site:
INIS
Size:
page(s) 1600-1606
Announcement Date:
Sep 12, 2011

Citation Formats

Melrose, D B. FARADAY ROTATION: EFFECT OF MAGNETIC FIELD REVERSALS. United States: N. p., 2010. Web. doi:10.1088/0004-637X/725/2/1600.
Melrose, D B. FARADAY ROTATION: EFFECT OF MAGNETIC FIELD REVERSALS. United States. doi:10.1088/0004-637X/725/2/1600.
Melrose, D B. 2010. "FARADAY ROTATION: EFFECT OF MAGNETIC FIELD REVERSALS." United States. doi:10.1088/0004-637X/725/2/1600. https://www.osti.gov/servlets/purl/10.1088/0004-637X/725/2/1600.
@misc{etde_21476697,
title = {FARADAY ROTATION: EFFECT OF MAGNETIC FIELD REVERSALS}
author = {Melrose, D B}
abstractNote = {The standard formula for the rotation measure (RM), which determines the position angle, {psi} = RM{lambda}{sup 2}, due to Faraday rotation, includes contributions only from the portions of the ray path where the natural modes of the plasma are circularly polarized. In small regions of the ray path where the projection of the magnetic field on the ray path reverses sign (called QT regions) the modes are nearly linearly polarized. The neglect of QT regions in estimating RM is not well justified at frequencies below a transition frequency where mode coupling changes from strong to weak. By integrating the polarization transfer equation across a QT region in the latter limit, I estimate the additional contribution {Delta}{psi} needed to correct this omission. In contrast with a result proposed by Broderick and Blandford, {Delta}{psi} is small and probably unobservable. I identify a new source of circular polarization, due to mode coupling in an asymmetric QT region. I also identify a new circular-polarization-dependent correction to the dispersion measure at low frequencies.}
doi = {10.1088/0004-637X/725/2/1600}
journal = {Astrophysical Journal}
issue = {2}
volume = {725}
place = {United States}
year = {2010}
month = {Dec}
}