Radio-loud active galactic nuclei (RLAGN) emit radiation across most of the electromagnetic
spectrum. The lower-energy component (Radio - Soft X-rays) is typically dominated by syn-
chrotron emission from non-thermal electrons in a relativistic jet. RLAGN are known to be highly
variable on both short (intra-day) and long (months to years) timescales. Most of the variability
observed in the optical and higher-energy regimes has been associated with sub-parsec to par-
sec scale emission regions located within the jet. In this study, we investigate the link between
observations and the kinematics of the sub-parsec-scale relativistic jet using 3D relativistic mag-
netohydrodynamic (RMHD) simulations. The simulations employ a two-component jet model,
consisting of a fast spine (Γ = 10) and a slower sheath (Γ = 3). The jet model features an initial
helical magnetic field with a magnitude of 50 mG in the spine and 5 mG in the sheath. In order
to simulate variability in the jet, a density perturbation is introduced at the jet inlet and allowed to
evolve with time. The simulations are carried out using a modified version of the PLUTO code,
which includes the injection of Lagrangian tracer particles, representing the non-thermal electron
distribution, used to model the synchrotron emission. The spectral energy distribution of these
particles are evolved over time to include effects from diffusive shock acceleration and radiative
cooling. This is used to calculate the I, Q, and U Stokes parameters, for arbitrary lines of sight,
accounting for relativistic transformations and light travel time. The Stokes parameters are used
to reproduce simulated light curves of the flux, polarization degree and polarization angle.