1997A&A...322...98H

Rotation measures for extragalactic sources, after selection to emphasize the large-scale structure of the Galactic magnetic field, reveal a striking antisymmetric pattern about the Galactic plane and the meridian through the Galactic Centre. This pattern is also observed in the rotation measures of pulsars with |b|>8°. The symmetry of the pattern, the magnitude of the rotation measures and the distance dependence of the pulsar rotation measures show that this pattern is not the result of local perturbations, but is on a large and possibly Galactic scale. This antisymmetric pattern and the existence of magnetic fields perpendicular to the plane in the Galactic Centre region, indicate that a dynamo mode of odd symmetry, possibly of A0 type, makes a substantial contribution to the magnetic fields in the thick disk and halo of our Galaxy, at least inside the Solar circle.