Variable fuelling of AGN jets: implications for jet power estimates and jet morphology up to 50 kpc

In AGN, chaotic cold accretion predicts pink noise "flickering" variability in the fuelling rate as cold clouds of material fall chaotically inwards towards the central accretion disk. We present high-resolution relativistic hydrodynamic simulations of jets with flickering jet power using the PLUTO code. We simulate the expected radio emission using a Lagrangian particle approach, capturing the effects of shock-heating together with synchrotron and adiabatic cooling. We present simulated radio emission maps, helping to bridge the gap between simulation and observation. We show that moderate rises in jet power can result in short-lived large increases in the radiative efficiency of the jet hotspot. We discuss the mechanism behind this hotspot brightening – namely the interaction of travelling shocks with a pre-existing forward and reverse shock structure at the jet head, which we term the "interacting shocks" mechanism. We present semi-analytical estimates for the expected level of hotspot brightening. Furthermore, we present a new relativistic magnetohydrodynamic simulation of a flickering jet, which we use to investigate interactions between the interacting shocks mechanism and magnetic field structures in the jet. Overall, we find that flickering can profoundly impact the dynamics, morphology and radiative efficiency of astrophysical jets, with significant implications for jet power estimates.