SKA in VLBI: Impact on Studies of Small Scale Structures in Active Galactic Nuclei

We discuss the advantages of an electronically steerable interferometer of a million square meters collecting area operating at cm-wavelengths as a phased array and in conjunction with other antennas in VLBI mode. With a sensitivity to μJy-level flux densities, a brightness temperature limit of TB = 10 4 K, and an expected dynamic range in future VLBI images of better than 10, the impact of SKA on the research on compact galactic and extragalactic radio sources will be virtually unpredictable, but certainly strong. In conjunction with future space VLBI missions and complementary to planned large interferometers operating at millimeter wavelengths, SKA bears the potential to revolutionize astronomy and our picture of the Universe. In this article we briefly outline the improvements expected from the use of SKA for VLBI in general. Then more specifically, we discuss the anticipated progress for the research on active galactic nuclei (AGN) and their powerful jets, emanating from hypothetical supermassive black holes. We will point out that beside a wealth of new details which SKA should reveal on jets, accretion disks and black holes, it will help to understand the relationship between the various types of active galactic nuclei (quasars & galaxies) and their cosmological evolution.