Abstract
Relativistic jets in active galactic nuclei (AGN) convert as much as half of
their energy into radiation. To explore the poorly understood processes that
are responsible for this conversion, we carry out fully 3D magnetohydrodynamic
(MHD) simulations of relativistic magnetized jets. Unlike the standard approach
of injecting the jets at large radii, our simulated jets self-consistently form
at the source and propagate and accelerate outward for several orders of
magnitude in distance before they interact with the ambient medium. We find
that this interaction can trigger strong energy dissipation of two kinds inside
the jets, depending on the properties of the ambient medium. Those jets that
form in a new outburst and drill a fresh hole through the ambient medium fall
victim to a 3D magnetic kink instability and dissipate their energy primarily
through magnetic reconnection in the current sheets formed by the instability.
On the other hand, those jets that form during repeated cycles of AGN activity
and escape through a pre-existing hole in the ambient medium maintain their
stability and dissipate their energy primarily at MHD recollimation shocks. In
both cases the dissipation region can be associated with a change in the
density profile of the ambient gas. The Bondi radius in AGN jets serves as such
a location.