Instabilities at recollimation shocks in MHD jets
arXiv:2510.01742 · doi:10.1051/0004-6361/202557516
Abstract
AGN jet structure and stability remain uncertain; recollimation shocks are linked to morphology and variability, but the role of downstream instabilities is still unclear. We aim to investigate how jet magnetization and other physical parameters influence the development of instabilities beyond the first recollimation shock. In particular, we focus on identifying the conditions under which the centrifugal instability (CFI) is effective. We perform high-resolution 2D and 3D simulations using the relativistic magnetohydrodynamics code PLUTO. The jets are initialized with a conical geometry and propagate into an ambient medium, and we follow by axisymmetric simulations how they evolve towards a steady-state. In 2D we explore a range of magnetizations (from 0 to 1), pressure contrasts, and inertia ratios to characterize the formation and evolution of recollimation shocks. The results are further evaluated using linear stability analysis to assess the growth and suppression of CFI. Finally, we perform 3D simulations of unstable and stable jets. We discuss how the different parameters of the axisymmetric steady solutions influence the location and strength of recollimation. We find that, even in moderately magnetized jets, =0.1, the CFI can still develop under suitable local conditions and disrupt the jet structure. This instability is governed by the jet radius, curvature, Lorentz factor, and magnetization, and is not always predictable from injection conditions. While magnetization can delay or locally suppress instability growth, it does not guarantee long-term jet stability. Our 3D results highlight the limitations of 2D models in capturing non-axisymmetric and nonlinear effects, and underline the complex interplay between magnetic confinement and destabilizing mechanisms. These findings have implications for interpreting variability, and polarization structure in AGN jets.
16 pages, 19 figures, accepted for publication in A&A
References in corpus (35)
- SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
- Array Programming with NumPy
- PLUTO: a Numerical Code for Computational Astrophysics
- Relativistic Jets in Active Galactic Nuclei
- The Structure and Dynamics of the Sub-parsec Scale Jet in M87 Based on 50 VLBA Observations Over 17 Years at 43 GHz
- On the Divergence-Free Condition in Godunov-Type Schemes for Ideal Magnetohydrodynamics: the Upwind Constrained Transport Method
- The Piecewise Parabolic Method for Multidimensional Relativistic Fluid Dynamics
- Constraining the location of the emitting region in Fermi blazars through rapid gamma-ray variability
- A five-wave HLL Riemann solver for relativistic MHD
- Recollimation Shocks in Magnetized Relativistic Jets
- 3D Relativistic Magnetohydrodynamic Simulations of Current-Driven Instability. I. Instability of a static column
- Causality and stability of cosmic jets
- Stochastic particle acceleration in the lobes of giant radio galaxies
- Three-dimensional Simulations of AGN Jets: Magnetic Kink Instability versus Conical Shocks
- Multi-Epoch Modeling of TXS 0506+056 and Implications for Long-Term High-Energy Neutrino Emission
- The structure of weakly-magnetized -ray burst jets
- Studies of the Jet in BL Lacertae I. Recollimation Shock and Moving Emission Features
- Linear stability analysis of magnetized relativistic jets: the nonrotating case
- Two-dimensional Numerical Study for Rayleigh-Taylor and Richtmyer-Meshkov Instabilities in Relativistic Jets
- Spectral evolution of flaring blazars from numerical simulations
- Reconfinement and Loss of Stability in Jets from Active Galactic Nuclei
- Linear stability analysis of magnetized relativistic rotating jets
- Recollimation shocks and radiative losses in extragalactic relativistic jets
- Magnetic inhibition of the recollimation instability in relativistic jets
- Rotation and toroidal magnetic field effects on the stability of two-component jets
- Particle acceleration in shearing flows: the self-generation of turbulent spine-sheath structures in relativistic MHD jet simulations
- An expanding one-zone model for studying blazars emission
- Internal instabilities in magnetized jets
- Probing an X-ray flare pattern in Mrk 421 induced by multiple stationary shocks: a solution to the bulk Lorentz factor crisis
- The polarization of the synchrotron radiation from a recollimated jet: application to high-energy BL Lacs
- PyPLUTO: a data analysis Python package for the PLUTO code
- Numerical Investigation of Instabilities in Over-pressured Magnetized Relativistic Jets
- Linear Stability Analysis of Relativistic Magnetized Jets: Methodology
- Linear Stability Analysis of Relativistic Magnetized Jets: The Minimalist Approach
- How do recollimation-induced instabilities shape the propagation of hydrodynamic relativistic jets?