We present results of axisymmetric magnetohydrodynamic (MHD) simulations investigating the launching of jets and outflows from a magnetically diffusive accretion disk. The time evolution of the disk structure is self-consistently taken into account. In contrast to previous works we have applied {\em spherical} coordinates for the numerical grid, implying substantial benefits concerning the numerical resolution and the stability of the simulation. Thanks to the new setup we were able to run simulations for more than 150,000 dynamical times on a domain extending 1500 inner disk radii with a resolution of up to 24 cells per disk height in the inner disk. Depending on the disk magnetization, jet launching occurs in two different but complementary regimes - jets driven predominantly by centrifugal or magnetic forces. These regimes differ in the ejection efficiency concerning mass, energy and angular momentum. We show that it is the {\em actual} disk magnetization and not so much the initial magnetization which describes the disk-jet evolution best. Considering the actual disk magnetization we also find that simulations starting with different initial magnetization evolve in a similar - typical - way as due to advection and diffusion the magnetic flux in the disk evolves in time. Exploring a new, modified diffusivity model we confirm the self-similar structure of the global jet-launching disk, obtaining power laws for the radial profiles of the disk physical variables such as density, magnetic field strength, or accretion velocity.
We investigate the launching mechanism of relativistic jets from black hole sources, in particular the strong winds from the surrounding accretion disk. Numerical investigations of the disk wind launching - the simulation of the accretion-ejection transition - have so far almost only been done for non-relativistic systems. From these simulations we know that resistivity, or magnetic diffusivity, plays an important role for the launching process. Here, we extend this treatment to general relativistic magnetohydrodynamics (GR-MHD) applying the resistive GR-MHD code rHARM. Our model setup conside…
We present fully three-dimensional magnetohydrodynamic jet launching simulations of a jet source orbiting in a binary system. We consider a time-dependent binary gravitational potential, thus all tidal forces that are experienced in the non-inertial frame of the jet-launching primary. We investigate systems with different binary separation, different mass ratio, and different inclination between the disk plane and the orbital plane. The simulations run over a substantial fraction of the binary orbital period. All simulations show similar local and global non-axisymmetric effects such as local …
In resistive and viscous magnetohydrodynamical (MHD) simulations we obtain axial jets launched from the innermost magnetosphere of a star-disk system. We found that in a part of the parameter space continuous asymmetric jets, which are propagating in opposite directions, are launched. We compare the speed of propagation and rotation of obtained jets with recent observational results.
We present MHD simulations exploring the launching, acceleration and collimation of jets and disk winds. The evolution of the disk structure is consistently taken into account. Extending our earlier studies, we now consider the self-generation of the magnetic field by an $α^2Ω$ mean-field dynamo. The disk magnetization remains on a rather low level, that helps to evolve the simulations for $T > 10,000$ dynamical time steps on a domain extending 1500 inner disk radii. We find a magnetic field of the inner disk similar to the commonly found open field structure, favoring magneto-centrifugal laun…
Turbulent magnetic diffusivity plays an important role for accretion disks and the launching of disk winds. We have implemented magnetic diffusivity, respective resistivity in the general relativistic MHD code HARM. This paper describes the theoretical background of our implementation, its numerical realization, our numerical tests and preliminary applications. The test simulations of the new code rHARM are compared with an analytic solution of the diffusion equation and a classical shock tube problem. We have further investigated the evolution of the magneto-rotational instability (MRI) in to…
We perform the most detailed analysis to date of the X-ray state of the Galactic black hole candidate GRS 1915+105 just prior to (0 to 4 hours) and during the brief (1 to 7 hour) ejection of major (superluminal) radio flares. A very strong model independent correlation is found between the 1.2 keV - 12 keV X-ray flux 0 to 4 hours before flare ejections with the peak optically thin 2.3 GHz emission of the flares. This suggests a direct physical connection between the energy in the ejection and the luminosity of the accretion flow preceding the ejection. In order to quantify this concept, we dev…
Astrophysical jets are launched from strongly magnetized systems that host an accretion disk surrounding a central object. The origin of the jet launching magnetic field is one of the open questions for modeling the accretion-ejection process. Here we address the question how to generate the accretion disk magnetization and field structure required for jet launching. Applying the PLUTO code, we present the first resistive MHD simulations of jet launching including a non-scalar accretion disk mean-field $α^2Ω$-dynamo in the context of large scale disk-jet simulations. Essentially, we find the $…
This is the first in a series of papers that introduces a new paradigm for understanding the jet in M87: a collimated relativistic flow in which strong magnetic fields play a dominant dynamical role. Here wefocus on the flow downstream of HST-1 - an essentially stationary flaring feature that ejects trails of superluminal components. We propose that these components are quad relativistic magnetohydrodynamic shock fronts (forward/reverse fast and slow modes) in a narrow jet with a helically twisted magnetic structure. And we demonstrate the properties of such shocks with simple one-dimensional …
Relativistic jets are launched from black hole (BH) X-ray binaries and active galactic nuclei when the disk accretion rate is below a certain limit (i.e., when the ratio of the accretion rate to the Eddingtion accretion rate, $\dot{m}$, is below about 0.01) but quenched when above. We propose a new paradigm to explain this observed coupling between the jet and the accretion disk by investigating the extraction of the rotational energy of a BH when it is surrounded by different types of accretion disk. At low accretion rates (e.g., when $\dot{m}\lesssim0.1$), the accretion near the event horizo…
Astrophysical jets are launched from strongly magnetized systems that host an accretion disk surrounding a central object. Here we address the question how to generate the accretion disk magnetization and field structure required for jet launching. We continue our work from Paper I (Mattia & Fendt 2020a), considering a non-scalar accretion disk mean-field $α^2Ω$-dynamo in the context of large scale disk-jet simulations. We now investigate a disk dynamo that follows analytical solutions of mean-field dynamo theory, essentially based only on a single parameter, the Coriolis number. We thereby co…
We perform resistive and viscous MHD simulations of axial jet launching from a magnetized thin accretion disk around a supermassive black hole. We compare the forces in our pseudo-Newtonian simulations for the Paczyński-Wiita and Kluźniak-Lee potentials. The results will help to find magnetic field configurations and physical parameters conducive to jet launching.
Many astrophysical sources, e.g., cataclysmic variables, X-ray binaries, active galactic nuclei, exhibit a wind outflow, when they reveal a multicolor blackbody spectrum, hence harboring a geometrically thin Keplerian accretion disk. Unlike an advective disk, in the thin disk, the physical environment, like, emission line, external heating, is expected to play a key role to drive the wind outflow. We show the wind outflow in a thin disk attributing a disk irradiation effect, probably from the inner to outer disks. We solve the set of steady, axisymmetric disk model equations in cylindrical coo…
We want to test if self-similar magneto-hydrodynamic (MHD) accretion-ejection models can explain the observational results for accretion disk winds in BHBs. In our models, the density at the base of the outflow, from the accretion disk, is not a free parameter, but is determined by solving the full set of dynamical MHD equations without neglecting any physical term. Different MHD solutions were generated for different values of (a) the disk aspect ratio ($\varepsilon$) and (b) the ejection efficiency ($p$). We generated two kinds of MHD solutions depending on the absence (cold solution) or pre…
The supermassive black hole candidate at the center of M87 drives an ultra-relativistic jet visible on kiloparsec scales, and its large mass and relative proximity allow for event horizon scale imaging with very long baseline interferometry at millimeter wavelengths (mm-VLBI). Recently, relativistic magneto-hydrodynamic (MHD) simulations of black hole accretion flows have proven capable of launching magnetically-dominated jets. We construct time-dependent disc/jet models of the innermost portion of the M87 nucleus by performing relativistic radiative transfer calculations from one such simulat…
High resolution X-ray spectra of black hole X-ray binaries (BHBs) show blueshifted absorption lines from disk winds which seem to be equatorial. Winds occur in the Softer (disk-dominated) states of the outburst and are less prominent or absent in the Harder (power-law dominated) states. We use self-similar magneto-hydrodynamic (MHD) accretion-ejection models to explain the disk winds in BHBs. In our models, the density at the base of the outflow from the accretion disk is not a free parameter, but is determined by solving the full set of dynamical MHD equations. Thus the physical properties of…
Ongoing millimeter VLBI observations with the Event Horizon Telescope allow unprecedented study of the innermost portion of black hole accretion flows. Interpreting the observations requires relativistic, time-dependent physical modeling. We discuss the comparison of radiative transfer calculations from general relativistic MHD simulations of Sagittarius A* and M87 with current and future mm-VLBI observations. This comparison allows estimates of the viewing geometry and physical conditions of the Sgr A* accretion flow. The viewing geometry for M87 is already constrained from observations of it…
We present results of magnetohydrodynamic (MHD) simulations of jet formation and propagation, discussing a variety of astrophysical setups. In the first approach we consider simulations of relativistic MHD jet formation, considering jets launched from the surface of a Keplerian disk, demonstrating numerically - for the first time - the self-collimating ability of relativistic MHD jets. We obtain Lorentz factors up to about 10 while acquiring a high degree of collimation of about 1 degree. We then present synchrotron maps calculated from the intrinsic jet structure derived from the MHD jet form…
Relativistically blurred reflection from the accretion disc provides a powerful probe of the extreme environments close to supermassive black holes; the inner regions of the accretion flow and the corona that produces the intense X-ray continuum. Techniques by which the geometry and extent of the corona can be measured through the observed X-ray spectrum are reviewed along with the evolution in the structure of the corona that is seen to accompany variations in the X-ray luminosity both on long and short timescales. Detailed analyses of the narrow line Seyfert 1 galaxies Markarian 335 and 1H07…
We explore the formation, energetics, and geometry of relativistic jets along with the variability of their central engine. We study both fast and slowly rotating black holes and address our simulations to active galaxy (AGN) centers and gamma ray burst (GRB) engines. The structured jets are postulated to account for emission properties of high energy sources across the mass scale, launched from stellar mass black holes in GRBs and from supermassive black holes in AGNs. Their active cores contain magnetized accretion disks and rotation of the Kerr black hole provides a mechanism for jet launch…
We investigate the launching of jets and outflows from magnetically diffusive accretion disks. Using the PLUTO code we solve the time-dependent resistive MHD equations taking into account the disk and jet evolution simultaneously. The main question we address is which kind of disks do launch jets and which kind of disks do not? In particular, we study how the magnitude and distribution of the (turbulent) magnetic diffusivity affect mass loading and jet acceleration. We have applied a turbulent magnetic diffusivity based on α-prescription, but have also investigate examples where the scale heig…
Remnant accretion disks formed in compact object mergers are an important ingredient in the understanding of electromagnetic afterglows of multi-messenger gravitational-wave events. Due to magnetically and neutrino driven winds, a significant fraction of the disk mass will eventually become unbound and undergo r-process nucleosynthesis. While this process has been studied in some detail, previous studies have typically used approximate initial conditions for the accretion disks, or started from purely hydrodynamical simulations. In this work, we analyse the properties of accretion disks formed…
The goal of this paper is to derive signatures of synchrotron radiation from state-of-the-art simulation models of collimating relativistic magnetohydrodynamic (MHD) jets featuring a large-scale helical magnetic field. We perform axisymmetric special relativistic MHD simulations of the jet acceleration region using the PLUTO code. The computational domain extends from the slow magnetosonic launching surface of the disk up to 6000^2 Schwarzschild radii allowing to reach highly relativistic Lorentz factors. The Poynting dominated disk wind develops into a jet with Lorentz factors of 8 and is col…
Magnetic fields connecting the immediate environs of rotating black holes to large distances appear to be the most promising mechanism for launching relativistic jets, an idea first developed by Blandford and Znajek in the mid-1970s. To enable an understanding of this process, we provide a brief introduction to dynamics and electromagnetism in the spacetime near black holes. We then present a brief summary of the classical Blandford-Znajek mechanism and its conceptual foundations. Recently, it has become possible to study these effects in much greater detail using numerical simulation. After d…
Hybrid Black Hole and Disk-Driven Jets: Steady Axisymmetric Ideal MHD Modeling
Peking University（北京大学）；Tsung-Dao Lee Institute, Shanghai Jiao-Tong University（上海交大凌波研究院）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Ningbo University（宁波大学）
We perform GR-MHD simulations of outflow launching from thin accretion disks. As in the non-relativistic case, resistivity is essential for the mass loading of the disk wind. We implemented resistivity in the ideal GR-MHD code HARM3D, extending previous works (Qian et al. 2017, 2018) for larger physical grids, higher spatial resolution, and longer simulation time. We consider an initially thin, resistive disk orbiting the black hole, threaded by a large-scale magnetic flux. As the system evolves, outflows are launched from the black hole magnetosphere and the disk surface. We mainly focus on d…
Magnetic, radiation pressure, and thermal driving are the three mechanisms capable of launching accretion disk winds. In X-ray binaries, radiation pressure is often not significant, as in many systems the luminosity is too low for driving due to continuum transitions yet too high for driving due to line transitions. This leaves thermal and magnetic driving as the contender launching mechanisms in these systems. Using Athena++, we perform axisymmetric ideal MHD simulations that include radiative heating and cooling processes appropriate for Compton heated winds to show that the inclusion of mag…
We report on a 120 ks Chandra/HETG spectrum of the black hole GRS 1915+105. The observation was made during an extended and bright soft state in June, 2015. An extremely rich disk wind absorption spectrum is detected, similar to that observed at lower sensitivity in 2007. The very high resolution of the third-order spectrum reveals four components to the disk wind in the Fe K band alone; the fastest has a blue-shift of v = 0.03c. Broadened re-emission from the wind is also detected in the first-order spectrum, giving rise to clear accretion disk P Cygni profiles. Dynamical modeling of the re-e…
We develop the theoretical model for the analytic description of hydrodynamic jets from protostellar disks employing the Beltrami-Bernoulli flow configuration of disk-jet structure. For this purpose we extend the standard turbulent viscosity prescription and derive several classes of analytic solutions using the flow parametrization in self-similar variables. Derived solutions describe the disk-jet structure, where for the first time jet properties are analytically linked with the properties of the accretion disk flow. The ratio of the jet ejection and disk accretion velocities is controlled b…
We examine the long-term evolution of accretion tori around black hole (BH) remnants of compact object mergers involving at least one neutron star, to better understand their contribution to kilonovae and the synthesis of r-process elements. To this end, we modify the unsplit magnetohydrodynamic (MHD) solver in FLASH4.5 to work in non-uniform three-dimensional spherical coordinates, enabling more efficient coverage of a large dynamic range in length scales while exploiting symmetries in the system. This modified code is used to perform BH accretion disk simulations that vary the initial magnet…
Relativistic, magnetized jets are observed to propagate to very large distances in many Active Galactic Nuclei (AGN). We use 3D relativistic MHD (RMHD) simulations to study the propagation of Poynting flux-driven jets in AGN. These jets are assumed already being launched from the vicinity ($\sim 10^3$ gravitational radii) of supermassive black holes. Jet injections are characterized by a model described in Li et al. (2006) and we follow the propagation of these jets to ~ parsec scales. We find that these current-carrying jets are always collimated and mildly relativistic. When $α$, the ratio o…
We present a detailed physical analysis of the jet launching mechanism of a circum-stellar disk that is located in a binary system. Applying 3D resistive MHD simulations, we investigate the local and global properties of the system, such as the angular momentum transport and the accretion and ejection mass fluxes. In comparison to previous works, for the first time, we have considered the full magnetic torque, the presence of an outflow, thus the angular momentum transport by vertical motion, and the binary torque. We discuss its specific 3D structure, and how it is affected by tidal effects. …
Global simulations of accretion flows onto perturbers embedded in magnetized disks -I. MRI and jet formation in ideal MHD
Charles University（查理大学）；Instituto de Astronomía, Universidad Nacional Autónoma de México（墨西哥国立自治大学天文研究所）；Niels Bohr International Academy, Niels Bohr Institute（尼尔斯·玻尔国际学院，尼尔斯·玻尔研究所）
We perform general relativistic, magnetohydrodynamic (GRMHD) simulations of binary neutron stars in quasi-circular orbit that merge and undergo delayed or prompt collapse to a black hole (BH). The stars are irrotational and modeled using an SLy or an H4 nuclear equation of state. To assess the impact of the initial magnetic field configuration on jet launching, we endow the stars with a purely poloidal magnetic field that is initially unimportant dynamically and is either confined to the stellar interior or extends from the interior into the exterior as in typical pulsars. Consistent with our …
We investigate the launching and stability of extragalactic jets through nonlinear magnetohydrodynamic (MHD) simulation and linear eigenmode analysis. In the simulations of jet evolution, a small-scale equilibrium magnetic arcade is twisted by a differentially rotating accretion disk. These simulations produce a collimated outflow which is unstable to the current driven m=1 kink mode for low rotational velocities of the accretion disk relative to the Alfven speed of the coronal plasma. The growth rate of the kink mode in the jet is shown to be inversely related to the rotation rate of the disk…
We interpret the 1.3mm VLBI observations made by the Event Horizon Telescope of the black hole in M87. It is proposed that, instead of being a torus of accreting gas, the observed annular ring is a rotating, magnetically-dominated ergomagnetosphere that can transmit electromagnetic angular momentum and energy outward to the disc through a combination of large scale magnetic torque and small scale instabilities. It is further proposed that energy can be extracted by magnetic flux threading the ergosphere through the efficient emission of long wavelength electromagnetic disturbances onto negativ…
We study the small scale magnetic reconnection above the radiative inefficient accretion flow around massive black hole via 2D magnetohydrodynamics (MHD) numerical simulation, in order to model the blob formation and ejection from the accretion flow around Sgr A*. The connection of both the newly emerging magnetic field and the pre-existing magnetic field is investigated to check whether blobs could be driven in the environment of black hole accretion disc. After the magnetic connection, both the velocity and temperature of the plasma can be comparable to the inferred physical properties at th…
Jets are a commonly observed phenomenon in post-asymptotic giant branch (post-AGB) binaries. Due to the orbital motion of the binary, the jet causes variable absorption in the Balmer profiles. In previous work, we have developed spatio-kinematic and radiative transfer models to reproduce the observed Balmer line variability and derive the spatio-kinematic structure of the jet and its mass-loss rate. Here, we apply our jet model to five post-AGB binaries with distinct Hα line variability and diverse orbital properties. Our models fit the Hα line variations very well. We estimate jet mass-loss r…
We perform local, vertically stratified shearing-box MHD simulations of protoplanetary disks (PPDs) at a fiducial radius of 1 AU that take into account the effects of both Ohmic resistivity and ambipolar diffusion (AD). The magnetic diffusion coefficients are evaluated self-consistently from a look-up table based on equilibrium chemistry. We first show that the inclusion of AD dramatically changes the conventional picture of layered accretion. Without net vertical magnetic field, the system evolves into a toroidal field dominated configuration with extremely weak turbulence in the far-UV ioniz…
Jet launching from the Kerr black hole magnetosphere: An electrogeodesic approach
Arnold Sommerfeld Center for Theoretical Physics（阿诺德·索末菲理论物理中心）；Univ Lyon, CNRS, ENS de Lyon, Laboratoire de Physique (LPENSL)（里昂大学，法国国家科学研究中心，里昂高等师范学院，物理实验室）；Departament de Física, EEBE, Universitat Politècnica de Catalunya（加泰罗尼亚理工大学，高等工程学院，物理系）；LUX, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université（巴黎天文台，PSL大学，法国国家科学研究中心，索邦大学）；Laboratoire de Mathématiques de Bretagne Atlantique, CNRS UMR 6205, Université de Bretagne Occidentale（布列塔尼西部大学，法国国家科学研究中心）
We conduct forward-modeling analysis based on our 2.5 dimensional magnetohydrodynamics (MHD) simulation of magnetic flux rope (MFR) formation and eruption driven by photospheric converging motion. The current sheet (CS) evolution during the MFR formation and eruption process in our MHD simulation can be divided into four stages. The current sheet (CS) evolution during the MFR formation and eruption process in our MHD simulation can be divided into four stages. The first stage shows the CS forming and gradually lengthening. Resistive instabilities that disrupt the CS mark the beginning of the s…
In this paper we explore the dynamics of radiative axisymmetric MHD jets at high resolution using AMR methods. The goal of the study is to determine both the dynamics and emission properties of such jets. To that end we have implemented microphysics enabling us to produce synthetic maps of H$α$ and [S II]. The jets are pulsed either sinusoidally or randomly via a time-dependent ejection velocity which leads to a complicated structure of internal shocks and rarefactions as has been seen in previous simulations. The high resolution of our simulations allows us to explore in great detail the effe…
Modelling the delayed shock-breakout emission following jet-launching binary neutron star mergers via relativistic magnetohydrodynamic simulations simulations
INAF, Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；INFN, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）
We suggest that the radio emission from the dwarf nova SS Cyg during outburst comes from magnetic activity that formed a corona (similar to coronae found in magnetically active stars), rather than from jets. We base our claim on the recent results of Laor & Behar, who found that when the ratio between radio and X-ray flux of accretion disks in radio-quiet quasars is as in active stars, Lr/Lx=10^{-5}, then most of the radio emission comes from coronae. Using observations from the literature we find that for SS Cyg during outburst Lr/Lx<10^{-5}. This does not mean jets are not launched during ou…
The accretion-ejection connection in the asymmetric Th 28 jet revealed by MUSE-NFM
Academia Sinica Institute of Astronomy and Astrophysics（中央研究院天文及天文物理研究所）；Department of Experimental Physics, Maynooth University（梅努斯大学实验物理系）；INAF—Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；School of Physics, University College Dublin（都柏林大学学院物理学院）；ESO（欧洲南方天文台）；Thüringer Landessternwarte（图林根州立天文台）
We have developed a numerical MHD model of the propeller candidate star AE Aqr using axisymmetric magneto-hydrodynamic (MHD) simulations. We suggest that AE Aqr is an intermediate polar-type star, where the magnetic field is relatively weak and an accretion disc may form around the white dwarf. The star is in the propeller regime, and many of its observational properties are determined by the disc-magnetosphere interaction. Comparisons of the characteristics of the observed versus modelled AE Aqr star show that the model can explain many observational properties of AE Aqr. In a representative …
We explore the pulsationally driven orbital mass ejection mechanism for Be star disc formation using isothermal, 3D magnetohydrodynamic (MHD) and hydrodynamic simulations. Non-radial pulsations are added to a star rotating at 95\% of critical as an inner boundary condition that feeds gas into the domain. In MHD, the initial magnetic field within the star is weak. The hydrodynamics simulation has limited angular momentum transport, resulting in repeating cycles of mass accumulation into a rotationally-supported disc at small radii followed by fall-back onto the star. The MHD simulation, convers…
The aim of this paper is to investigate the properties of accretion disks threaded by a weak vertical magnetic field, with a particular focus on the interplay between MHD turbulence driven by the magnetorotational instability (MRI) and outflows that might be launched from the disk. For that purpose, we use a set of numerical simulations performed with the MHD code RAMSES in the framework of the shearing box model. We concentrate on the case of a rather weak vertical magnetic field such that the initial ratio beta0 of the thermal and magnetic pressures in the disk midplane equals 10^4. As repor…
