Numerical analysis of long-term variability of AGN jets through RMHD simulations

Abstract

Relativistic AGN (active galactic nucleus) jets exhibit multitime-scale variability and a broad-band non-thermal spectrum extending from radio to gamma-rays. These highly magnetized jets are prone to undergo several magnetohydrodynamic (MHD) instabilities during their propagation in space and could trigger jet radiation and particle acceleration. This work aims to study the implications of relativistic kink mode instability on the observed long-term variability in the context of the twisting in-homogeneous jet model. To achieve this, we investigate the physical configurations preferable for forming kink mode instability by performing high-resolution 3D relativistic MHD simulations of a portion of highly magnetized jets. In particular, we perform simulations of cylindrical plasma column with Lorentz factor ≥5 and study the effects of magnetization values and axial wavenumbers with decreasing pitch on the onset and growth of kink instability. We have confirmed the impact of axial wavenumber on the dynamics of the plasma column including the growth of the instability. In this work, we have further investigated the connection between the dynamics of the plasma column with its time-varying emission features. From our analysis, we find a correlated trend between the growth rate of kink mode instability and the flux variability obtained from the simulated light curve. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.