General relativistic magnetohydrodynamic simulations of the jet formation and large-scale propagation from black hole accretion systems

Abstract

The formation and large-scale propagation of Poynting-dominated jets produced by accreting, rapidly rotating black hole systems are studied by numerically integrating the general relativistic magnetohydrodynamic equations of motion to follow the self-consistent interaction between accretion discs and black holes. This study extends previous similar work by studying jets till t ≈ 10 4 GM/c 3 out to r ≈ 10 4 GM/c 2 , by which the jet is superfast magnetosonic and moves at a lab-frame bulk Lorentz factor of ∼ 10 with a maximum terminal Lorentz factor of ∞ 10 3 . The radial structure of the Poynting-dominated jet is piece-wise self-similar, and fits to flow quantities along the field line are provided. Beyond the Alfvén surface at r ∼ 10-100GM/c 2 , the jet becomes marginally unstable to (at least) current-driven instabilities. Such instabilities drive shocks in the jet that limit the efficiency of magnetic acceleration and collimation. These instabilities also induce jet substructure with 3 15. The jet is shown to only marginally satisfy the necessary and sufficient conditions for kink instability, so this may explain how astrophysical jets can extend to large distances without completely disrupting. At large distance, the jet angular structure is Gaussian-like (or uniform within the core with sharp exponential wings) with a half-opening angle of ≈5 • and there is an extended component out to ≈ 27 • . Unlike in some hydrodynamic simulations, the environment is found to play a negligible role in jet structure, acceleration, and collimation as long as the ambient pressure of the surrounding medium is small compared to the magnetic pressure in the jet.

Central engines of Gamma Ray Bursts. Magnetic mechanism in the collapsar model.

“…To some extent this may reflect real physical processes [11,27,28,29] but numerical diffusion and resistivity are likely to play a significant part too. In any case, the total energy is conserved in the simulations and we do not expect these numerical problems to effect the dynamics of blast.…”

“…Previous studies, with simplified setting and micro physics, have already demonstrated that this problem can be addressed with modern computational tools (e.g. [11]) and invite to explore progressively more realistic models.…”

Key Science Observations of AGNs with KaVA array

“…Although magnetic driven scenario of relativistic jets is widely discussed (e.g., [1]; [2]), there is no conclusive observational evidence to prove it. In order to explore jet formation processes by a central engine composed of a supermassive black hole and accreting matter onto it, Very Long Baseline Interferometer (VLBI) is one of the most powerful tools because they can probe innermost regions of relativistic jets with its high spatial resolution.…”

A new multiwavelength lepto-hadronic model of astrophysical jet emission

“…These studies all share the common approach of modelling only the non-thermal emission from the jet. However, the fundamental plane of black hole accretion [28,12,33] as well as works based on general relativistic magnetohydrodynamical (GRMHD) simulations [26,27,2,9] support the idea that accretion discs, bases of jets and jets themselves are all connected, forming one inflow-outflow system. To understand the power in jets and their content, and to model multiwavelength observations of accreting black holes, it is therefore essential to study the system as a whole, thermal and non-thermal sources of emission from the accretion disc and the jets altogether.…”