Simulation of Shock-Shock interaction in parsec-scale jets
  The analysis of the radio light curves of the blazar CTA102 during its 2006 flare revealed a possible interaction between a standing shock wave and a traveling one. In order to better understand this highly non-linear process, we used a relativistic hydrodynamic code to simulate the high energy interaction and its related emission. The calculated synchrotron emission from these simulations showed an increase in turnover flux density, $S_{m}$, and turnover frequency, $\nu_{m}$, during the interaction and decrease to its initial values after the passage of the traveling shock wave. 
Christian M. Fromm, Manel Perucho, Eduardo Ros, Petar Mimica, Tuomas   Savolainen, Andrei P. Lobanov and J. Anton Zensus
astro-ph.HE astro-ph.CO