The Local Galactic Magnetic Field

The Galactic magnetic field is analyzed based on the large amount of pulsar rotation measures (RMs) now available, and regions of the sky suspected of producing anomalous RMs are discussed. The North Polar Spur appears to cause large positive RMs in the region l between 0 and 60 deg and b between 0 and 60 deg, and thus causes a systematic bias in modeling if the pulsars in the region are not flagged. Using only unflagged pulsars within D = 3 kpc and a longitudinal model of the local field, the strength is found to be B(0) = 1.6 + or - 0.3 microgauss in the direction l(B) = 96 deg + or - 4 deg, with a reversal at D(r) = 600 + or - 80 pc toward the inner Galaxy. A concentric-ring model is found to be superior to a bisymmetric spiral model as a fit to the data without the 3 kpc restriction, with a strength of B0 = 1.3 + or - 0.2 microgauss at the position of the sun and a reversal at D(r) = 650 + or - 90 pc toward the Galactic center.