MODELING EXTRAGALACTIC JETS

Extragalactic jets were discovered and initially studied by radio astronomers in connection with extended radio sources. At present, the combination of jets and disks is considered the crucial element in unification models for all active galactic nuclei (AGNs). The acceleration and propagation conditions of jets, together with the aspect ratio of the disk/jet geometry with respect to the observer, shape the morphologies of AGNs. However, these phenomenological models are very complex from the physical and mathematical point of view, as they involve different elements of the theories of gravitation, fluid dynamics, and electrodynamics in a highly nonlinear combination and in conditions not easily reproducible in laboratory plasma or fluid experiments. In the last ten years, theorists have attacked the subject with advanced analytical and numerical methods, and some important results have already been established that confirm the global scenario, although we are still far from a complete physical interpretation. This review summarizes the main results on the art of jet modeling, emphasizing the limitations of the available models and the possibility of new developments.