Radio polarization and RM structure at high Galactic latitudes

We present WSRT observations at low frequencies (315-388 MHz) of the diffuse polarized emission in an area of 6 x 6 at high Galactic latitude. Polarized emission is found to be ubiquitous with typical levels of about 3-5 K brightness temperature with a generally mottled structure. The Rotation Measure (RM) of the emission varies between values of -5 to +20 rad m(-2). Most of the polarized emission appears Faraday thin with a single unresolved valued for the RM. The data suggest both inhomogeneous as well as dissimilar distribution functions of the synchrotron emitting and Faraday rotating media along the line of sight. The systematic patterns in the RM at this high Galactic latitude of +71 degrees also provide evidence for significant variations in the vertical component of the local Galactic magnetic field at a level of 1 mu Gauss. The potential for Galactic polarimetry at even lower frequencies using LOFAR and SKA is briefly discussed. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.