Aller The link between the black hole and accretion disk at the heart of active galactic nuclei (AGN), and the radio jets commonly observed in these sources and apparently emanating from the central engine, remains an unanswered question. Past work has successfully treated the radio jets as hydrodynamical flows with passive magnetic fields, even though the magnetic energy must be high. This research will explore the connection between these regimes, using multi-frequency radio polarimetry observations to measure directly the magnetic field strength and orientation. Both single dish and interferometric observations of linear and circular polarization at multiple frequencies, over timescales of weeks to decades, are necessary and will be obtained, and interpreted using associated modeling. A valuable by-product will be information on particle composition and particle energy distribution, fundamental jet properties which remain unknown. The database of unique measurements will be made readily available, and the research will help maintain one of the few radio telescopes available in the US for hands-on student training. ***
