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Nordita Astrophysics seminars

Faraday signature of magnetic helicity from reduced depolarization

by Axel Brandenburg (Nordita)

Europe/Stockholm
122:026 ()

122:026

Description
Using analytic reasoning and one-dimensional numerical models, we show that a helical magnetic field can cancel the Faraday depolarization resulting from the superposition of Faraday-rotated polarization planes from a spatially extended source. The presence of positive magnetic helicity can be detected in regions of positive rotation measure (RM), and negative helicity in regions of negative RM. When these conditions are not obeyed, polarized emission is shifted into unobservable (imaginary) wavelengths. However, the simultaneous presence of two magnetic components with opposite signs of helicity is shown to possess signatures that can be quantified through polarization peaks at specific wavelengths and the gradient of the phase of the Faraday dispersion function. We expect the Square Kilometre Array to provide an opportunity to detect fields with such properties.

NORDITA-2014-001