Magnetic field geometry of the broad line radio galaxy 3C111

Abstract Very Long Baseline Polarimetric observations of the Broad Line Radio galaxy 3C111 performed in July and September of 1996 at 8 and 43 GHz reveal rapidly evolving parsec-scale radio structure after a large millimetre outburst. The B-field geometry is not simple. We present a first analysis of possible Faraday and optical depth effects based on a comparison of the polarization images for the two frequencies.