Pulsar rotation measures and the galactic magnetic field

Abstract

The rotation measures and dispersion measures of 185 pulsars are used to delineate the galactic magnetic field. The nearer pulsars, with dispersion measure DM < 40 pc cm−3, indicate that the local magnetic field is about 2–3 μG, directed toward l=90°. The more distant pulsars indicate that the field at smaller galactocentric distances is reversed and stronger. The comparatively low rotation measures of extragalactic sources in other directions, including the direction of the anticenter, indicate the existence of other reversals.