Milliarcsecond Polarization Studies of Compact ExtragalacticRadio Sources

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The distributions of the linear polarization of radio wavelength emission from compact radio sources will be studied at milliarcsecond resolution using the technique of the Very Long Baseline Interferometry (VLBI). These radio sources are associated with the nuclei of quasars and active galaxies, where enormous amounts of energy are emitted on very short timescales, probably due to the infall of material onto a supermassive black hole. The energy manifests itself as radiation on all parts of the electromagnetic spectrum. At radio wavelengths we see compact radio-emitting `cores' and `jet-like' features, that vary rapidly in both total intensity and polarization. In many sources, bright knots of emission appear to be moving down the jets at several times the speed of light. The goals of the observations are: (1), to map the topology of the magnetic field structures and to study their evoulution; (2), to obtain kinematic and geometric information to constrin models of superluminal sources; (3), to help understand the differences between differnt classes of compact radio sources; (4), to probe the plasma surrounding the rdio sources in the innermost regions of quasars and active galactic nuclei; and (5), to study the relationship between the milliarcsecond radio structure and the large scale (much greater than 1 arcsecond) jets and lobes found in extended radio sources.