Faraday signature of magnetic helicity from reduced depolarization
Nordita Astrophysics seminars
Wednesday 08 January 2014
to 14:15 at
Axel Brandenburg (Nordita & Astronomy Department)
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
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.