Published online by Cambridge University Press: 07 February 2017
Optical and radio measurements of polarization can be combined to find the configuration of the magnetic field throughout the Crab Nebula. The component in the line of sight is found from the radio rotation measure.
New measurements of polarisation at 11 cm with a resolution of 7′ x 14′ are combined with previous results to show that the rotation measure is fairly uniform and near −25 rad m−2 near the centre, but that it becomes irregular near the edges. It rises to 300 rad m−2 in the filaments, possibly indicating a concentration of electrons about 10–100 cm−3.