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2001MNRAS.325..649F - Mon. Not. R. Astron. Soc., 325, 649-664 (2001/August-1)
Structures in the rotation measure sky.
FRICK P., STEPANOV R., SHUKUROV A. and SOKOLOFF D.
Abstract (from CDS):
We consider separately low-latitude sources at |b|<10° and, using the model of electron density distribution of Cordes et al., we estimate magnetic field strength by comparing the model wavelet transform with that of the real data. Independent estimates of the mean magnetic field strength in the Orion arm using low- and high-latitude sources converge to 1.4±0.3µG. Rotation measures of low-latitude sources provide a clear indication of a magnetic field reversal at a distance 0.6-1kpc towards the Galactic Centre. Our analysis has revealed for the first time the extension of the reversal in the Carina arm. Low-latitude sources from the catalogue of Broten et al. indicate a magneto-ionic structure in the direction of the Perseus arm with the magnetic field direction reversed with respect to that in the Orion arm. The extent of the region with reversed magnetic field near the Sun is 3kpc or more in the azimuthal direction. The average pitch angle of magnetic field in the nearby spiral arms is 15°, and the mean field strength in the Sagittarius-Carina and Perseus arms is 1.7±0.3µG and 1.4±1.2µG, respectively. The line-of-sight magnetic field in Loop I is estimated as 0.9±0.3µG.
We find firm evidence of a dominant even symmetry of the local mean magnetic field with respect to the Galactic equator. Our results are compatible with a moderate large-scale north-south asymmetry, with the magnetic field in the southern hemisphere being stronger in a region of at least 3kpc in size. It cannot be excluded, however, that the asymmetry is local and results from vertical bending of magnetic lines in a region of about 400pc in size, with the Sun being located close to the top of a magnetic loop, the magnetic field of which is 0.5µG stronger than the average field.
Abstract Copyright: The Royal Astronomical Society
Journal keyword(s): magnetic fields - polarization - methods: data analysis - ISM: magnetic fields - Galaxy: structure
Simbad objects: 9
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