HYDRODYNAMICAL MODELS OF SUPERLUMINAL SOURCES

We present numerical simulations of the generation, evolution, and rad io emission of superluminal components in relativistic jets. We perfor m the fluid dynamical calculations using a relativistic time-dependent code based on a high-resolution shock-capturing;scheme, and then we c alculate the radio emission by integrating the transfer equations for synchrotron radiation. These simulations show that a temporary increas e in the flow velocity at the base of the jet produces a moving pertur bation that contains both a forward and a reverse shock and is trailed by a rarefaction. The perturbation appears in the simulated maps as a region of enhanced emission moving downstream at a superluminal appar ent velocity. Interactions of the perturbation with the underlying ste ady jet result in changes in the internal brightness distribution of t he superluminal component, which are manifested as low-level fluctuati ons about the long-term evolution of both the apparent velocity and th e exponential decay of the light curves.