We investigate the feedback of the stellar jets on the surrounding interstellar gas based on 2D and 3D simulations applying HD and MHD module of PLUTO 4.2 code. The main question we address is whether the stellar jet can be considered as a turbulence driver into the interstellar gas. In addition, we investigate the most effective circumstances in which the driven turbulence is larger and can survive for a longer time scale in the ambient gas.
We present a case study of different parameters runs including the jet Mach number, the initial jet velocity field and the background magnetic field geometries and the interacting jets. Also, we study the environmental effects on the jet-gas interaction by considering the non-homogeneous surrounding gas containing the clumps in the model setup.
Among different setups, we find that for (1) a higher jet Mach number, (2) a rotating jet, 16 pages(3) a jet propagating in a magnetized environment, (4)a jet propagating in a non-homogeneous environment, and (5) the interacting jets more fluctuations and random motions are produced in the entrained gas which can survive for a longer time scale. In addition, we perform the 3D simulations of jet-ambient gas interaction and we find that the amount of (subsonic-supersonic) fluctuations increases compared to the axisymmetric run and the entrained gas gains higher velocities in a 3D run. In total, we confirm the previous finding that the stellar jets can transfer the turbulence on neighboring regions and are not sufficient drivers of the large-scale supersonic turbulence in molecular clouds.
We propose a novel model to produce ultrahigh-energy cosmic-rays (UHECRs) in gamma-ray burst jets. After the prompt gamma-ray emission, hydrodynamical turbulence is excited in the GRB jets at or before the afterglow phase. The mildly relativistic turbulence stochastically accelerates protons. The acceleration rate is much slower than the usual first-order shock acceleration rate, but in this case it can be energy-independent. The resultant UHECR spectrum is so hard that the bulk energy is concentrated in the highest energy range, resulting in a moderate requirement for the typical cosmic ray l…
Astrophysical accretion is arguably the most prevalent physical process in the Universe; it occurs during the birth and death of individual stars and plays a pivotal role in the evolution of entire galaxies. Accretion onto a black hole, in particular, is also the most efficient mechanism known in nature, converting up to 40% of accreting rest mass energy into spectacular forms such as high-energy (X-ray and gamma-ray) emission and relativistic jets. Whilst magnetic fields are thought to be ultimately responsible for these phenomena, our understanding of the microphysics of MHD turbulence in ac…
We study the structures of ultra-relativistic jets injected into the intracluster medium (ICM) and the associated flow dynamics, such as shocks, velocity shear, and turbulence, through three-dimensional relativistic hydrodynamic (RHD) simulations. To that end, we have developed a high-order accurate RHD code, equipped with a weighted essentially non-oscillatory (WENO) scheme and a realistic equation of state (Seo et al. 2021, Paper I). Using the code, we explore a set of jet models with the parameters relevant to FR-II radio galaxies. We confirm that the overall jet morphology is primarily det…
Blazars show variability on timescales ranging from minutes to years, the former being comparable to and in some cases even shorter than the light-crossing time of the central black hole. The observed gamma-ray lightcurves can be described by a power-law power density spectrum (PDS), with a similar index for both BL Lacs and flat-spectrum radio quasars. We show that this variability can be produced by turbulence in relativistic jets launched by magnetically arrested accretion flows (MADs). We perform radiative transport calculations on the turbulent, highly-magnetized jet launching region of a…
I discuss three mutually-supportive notions or assumptions regarding jets and accretion. The first is magnetocentrifugal acceleration (MCA), the overwhelmingly favored mechanism for the production of jets in most steady accreting systems. The second is the zero-torque inner boundary condition. The third is that effective viscous dissipation is like real dissipation, leading directly to heating. All three assumptions fit nicely together in a manner that is simple, persuasive, and mutually-consistent. All, I argue, are incorrect. For concreteness I focus on protostars. Magnetohydrodynamic (MHD) …
Diffusive shock acceleration (DSA) at relativistic shocks is widely thought to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud active galactic nuclei such as blazars. Such acceleration can produce the non-thermal particles that emit the broadband continuum radiation that is detected from extragalactic jets. An important recent development for blazar science is the ability of Fermi-LAT spectroscopy to pin down the shape of the distribution of the underlying non-thermal particle population. This paper highlights how multi-wavelength spectra spann…
Electrons emitting non-thermal photons in blazars are possibly accelerated by turbulences developed in jets. In this paper, we consider the case so-called hard-sphere scattering as an interaction model between turbulences and electrons, in which the acceleration timescale is independent of the electron energy. We numerically simulate broad-band emission from blazar jets with a one-zone time-dependent code, taking into account the turbulence acceleration. Our model reproduces various blazar spectra with simple assumptions, such as constant particle injection rate, constant diffusion coefficient…
In many observed galaxy clusters, jets launched by the accretion process on to supermassive black holes, inflate large-scale cavities filled with energetic, relativistic plasma. This process is thought to be responsible for regulating cooling losses, thus moderating the inflow of gas on to the central galaxy, quenching further star formation and maintaining the galaxy in a red and dead state. In this paper, we implement a new jet feedback scheme into the moving mesh-code arepo, contrast different jet injection techniques and demonstrate the validity of our implementation by comparing against s…
Centres of galaxy clusters must be efficiently reheated to avoid a cooling catastrophe. One potential reheating mechanism is anisotropic thermal conduction, which could transport thermal energy from intermediate radii to the cluster center. However, if fields are not re-randomised, anisotropic thermal conduction drives the heat buoyancy instability (HBI) which reorients magnetic field lines and shuts off radial heat fluxes. We revisit the efficiency of thermal conduction under the influence of spin-driven AGN jets in idealised magneto-hydrodynamical simulations with anisotropic thermal conduct…
Particle acceleration in magnetized relativistic jets still puzzles theorists, specially when one tries to explain the highly variable emission observed in blazar jets or gamma-ray bursts putting severe constraints on current models. In this work we investigate the acceleration of particles injected in a three-dimensional relativistic magnetohydrodynamical jet subject to current driven kink instability (CDKI), which drives turbulence and fast magnetic reconnection. Test protons injected in the nearly stationary snapshots of the jet, experience an exponential acceleration up to a maximum energy…
Fast magnetic reconnection events can play an important role in accretion disk systems. A potential model to explain the non-thermal very-high-energy (VHE) emission (from GeV to TeV) observed in black-hole binaries (BHBs) and Active Galatic Nuclei (AGNs) can be attributed to fast magnetic reconnection induced in the turbulent corona of accretion disks and/or jets. In this work, we will discuss the results of global general relativistic MHD (GRMHD) simulations of accretion disks around black holes, whose turbulence is naturally driven by MHD instabilities, such as the magnetorotational instabil…
Turbulence in an accretion disk launches Alfvén waves (AWs) that propagate away from the disk along magnetic field lines. Because the Alfvén speed varies with distance from the disk, the AWs undergo partial non-WKB reflection, and counter-propagating AWs subsequently interact, causing AW energy to cascade to small scales and dissipate. To investigate this process, we introduce an Elsasser-like formulation of general relativistic MHD (GRMHD) and develop the theory of general relativistic reduced MHD in an inhomogeneous medium. We then derive a set of equations for the mean-square AW amplitude $…
We explore constraints imposed by shear-driven instabilities on the acceleration of energetic particles in relativistic shearing flows. We show that shearing layers in large-scale AGN jets are likely to encompass a sizeable fraction ($\geq 0.1$) of the jet radius, requiring seed injection of GeV electrons for efficient acceleration. While the diffusion process may depend on pre-developed turbulence if injection occurs at higher energies, electron acceleration to PeV and proton acceleration to EeV energies appears possible within the constraints imposed by jet stability.
Extragalactic radio sources have been classified into two classes, Fanaroff-Riley I and II, which differ in morphology and radio power. Strongly emitting sources belong to the edge-brightened FR II class, and weakly emitting sources to the edge-darkened FR I class. The origin of this dichotomy is not yet fully understood. Numerical simulations are successful in generating FR II morphologies, but they fail to reproduce the diffuse structure of FR Is. By means of hydro-dynamical 3D simulations of supersonic jets, we investigate how the displayed morphologies depend on the jet parameters. Bow sho…
We examine the possible role of turbulence in feeding the emission of gamma-ray bursts (GRBs). Turbulence may develop in a GRB jet as the result of hydrodynamic or current-driven instabilities. The jet carries dense radiation and the turbulence cascade can be damped by Compton drag, passing kinetic fluid energy to photons through scattering. We identify two regimes of turbulence dissipation: (1) "Viscous" - the turbulence cascade is Compton damped on a scale $\ell_{\rm damp}$ greater than the photon mean free path $\ell_\star$. Then turbulence energy is passed to photons via bulk Comptonizatio…
The possibility of using lensed relativistic jets on very small angular scales to construct proper models of spiral lens galaxies and to independently determine the Hubble constant is considered. The system B0218+357 is used as an example to illustrate that there exists a great choice of model parameters adequately reproducing its observed large-scale properties but leading to a significant spread in the Hubble constant. The jet image position angle is suggested as an additional parameter that allows the range of models under consideration to be limited. It is shown that the models for which t…
A single measurement of linear polarization of a nonthermal source provides direct information about the mean direction and level of ordering of the magnetic field. Monitoring of the polarization in blazars, combined with millimeter-wave VLBI imaging in both total and polarized intensity, has the potential to determine the geometry of the magnetic field. This is a key probe of the physical processes in the relativistic jet, such as ordered field components, turbulence, magnetic reconnections, magnetic collimation and acceleration of the jet flow, particle acceleration, and radiative processes …
The rotational energy of a black hole can be extracted via the Blandford-Znajek mechanism and numerical simulations suggest a strong dependence of the power of the produced jet on the black hole spin. A recent study has found no evidence for a correlation between the spin and the power of steady jets. If the measurements of the spin and of the jet power are correct, it leads one to conclude that steady jets are not powered by the black hole spin. In this paper, I explore another possibility: I assume that steady jets are powered by the spin and I check if current observations can be explained …
Jets are ubiquitous in the Universe. They are collimated outflows whose origin is associated to an accretion disc and a central object, and can be very powerful non-thermal emitters. Jets form in active galactic nuclei, gamma-ray bursts, microquasars, and young stellar objects. Galactic jets emitting non-thermal emission are typically associated to microquasars, although the jets of massive young stellar objects are also non-thermal sources. The production of non-thermal radiation, in particular radio synchrotron emission, is a clear indication that particle acceleration is taking place in the…
The mechanism of turbulent viscosity is the central question in investigations of turbulence. This is also the case in the accretion disk theory, where turbulence is considered to be responsible for the outward transport of angular momentum in the accretion disk. In turbulent flows, vortices transport momentum over their length scales providing the mechanism of viscosity that is controlled by mass entrainment. We have earlier proposed an entrainment model for the particular case of the relativistic jets in the radio galaxy 3C31. In this paper, we further constrain the model parameters. The mod…
