The Blazar Paradigm: Synchro-Compton Emission from Relativistic Jets

Abstract

I review the current paradigm for nonthermal emission from jets in blazars. The evidence for relativistically flowing jets seems to be more compelling than the case for incoherent synchrotron and self-Compton emission in these objects. I discuss some of the important aspects of current observations of rapid variability at radio frequencies, and stress that one must be careful when calculating the Doppler factor that saves us from the inverse Compton “catastrophe.” I discuss the possibilities for the nature of the VLBI components and present evidence that, at high frequencies, the core is a standing shock wave (Mach disk), while the superluminal components are propagating shocks. I expect that high-frequency and space VLBI will resolve many of the major outstanding issues.