Pulsar Rotation and Dispersion Measures and the Galactic Magnetic Filed.

Observations of pulsar polarization and pulse time of arrival at frequencies between 250 and 500 MHz have been used to determine rotation and dispersion measures for 19 and 21 pulsars, respectively. These measurements have been used to calculate mean line-of-sight components of the magnetic field in the the path to the pulsars. These and other observations show that there is probably no contribution to the observed rotation measure from the pulsar itself. Low4atitude, low-dispersion pulsars are observed to have strong field components, and a strong dependence of rotation-measure sign on galactic longitude has been found. The observations are consistent with a relatively uniform field of about 3.5 microgauss directed toward about I = 90 in the local region, but appear to he inconsistent with the helical model for the local field.