Structure and Emission of Parsec-Scale Jets in Quasars

Abstract

Abstract. The moving knots observed in VLBI of compact quasars are due to off-axis substructures in the parsec-scale jets which are dragged along by the underlying plasma flow. This is suggested by detailed MHD models for the structure of relativistic jets on the parsec-scale that are based on exact solutions of the nonlinear Grad-Schluter-Shafranov equation in the asymptotic domain. These jet models are characterized by a current-carrying core and a current-free envelope. The corresponding core-radius RC = UPRL is related to the poloidal jet velocity u p and the light cylinder radius RL generated by the rotation of the magnetic surfaces. The Poynting flux, which has an inhomogeneous distribution in the jet, provides an off-axis energy reservoir that could be tapped and converted into particle acceleration by non-axisymmetric instabilities in the core-jet structure. Evidence is presented that quasi-periodic synchrotron emission (in the nt-optical) and inverse Compton emission (in X-and 7-rays) from freshly accelerated electrons are due to a lighthouse effect of the rotating knots.