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Paper: Magnetic Fields in Disks, Spiral Arms, and Bars
Volume: 396, Formation and Evolution of Galaxy Disks
Page: 35
Authors: Beck, R.
Abstract: Total magnetic fields in spiral galaxies, as observed through their total synchrotron emission, are strongest (up to 30 μG) in the spiral arms. The field in the arms is mostly turbulent or tangled. Polarized synchrotron emission shows that the resolved regular fields are generally strongest in the interarm regions (up to 15 μG), sometimes forming ‘magnetic arms’ parallel to the optical arms. The observed large-scale spiral patterns of Faraday rotation in a few spiral galaxies reveal coherent regular fields, as predicted by dynamo models. In galaxies with massive bars, the polarization pattern follows the gas flow. However, around strong shocks in bars, the compression of the regular field is much lower than that of the gas; the regular field decouples from the cold gas and is strong enough to affect the flow of the diffuse warm gas.
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