ON MAGNETIC SELF-COLLIMATION OF RELATIVISTIC JETS

2010 ◽  
Vol 19 (06) ◽  
pp. 689-694
Author(s):  
N. GLOBUS ◽  
V. CAYATTE ◽  
C. SAUTY
Keyword(s):  
Black Hole ◽  
Total Energy ◽  
Ideal Fluid ◽  
Polar Axis ◽  
Kerr Metric ◽  
Relativistic Jets ◽  
Simple Criterion ◽  
General Relativistic ◽  
Time Splitting ◽  
Relativistic Magnetohydrodynamics

We present a semi-analytical model using the equations of general relativistic magnetohydrodynamics (GRMHD) for jets emitted by a rotating black hole. We assume steady axisymmetric outflows of a relativistic ideal fluid in Kerr metrics. We express the conservation equations in the frame of the FIDucial Observer (FIDO or ZAMO) using a 3+1 space–time splitting. Calculating the total energy variation between a non-polar field line and the polar axis, we extend to the Kerr metric the simple criterion for the magnetic collimation of jets obtained for a nonrotating black hole by Meliani et al.10 We show that the black role rotation induced a more efficient magnetic collimation of the jet.

scholarly journals Magnetic collimation of relativistic jets: the role of the black hole spin

2010 ◽  
Vol 6 (S274) ◽  
pp. 246-248
Author(s):  
N. Globus ◽  
C. Sauty ◽  
V. Cayatte
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Polar Axis ◽  
Kerr Metric ◽  
Relativistic Jets ◽  
Self Similarity ◽  
Simple Criterion ◽  
Frame Dragging ◽  
Grmhd Equations

AbstractAn ideal engine for producing ultrarelativistic jets is a rapidly rotating black hole threaded by a magnetic field. Following the 3+1 decomposion of spacetime of Thorne et al. (1986), we use a local inertial frame of reference attached to an observer comoving with the frame-dragging of the Kerr black hole (ZAMO) to write the GRMHD equations. Assuming θ-self similarity, analytical solutions for jets can be found for which the streamline shape is calculated exactly. Calculating the total energy variation between a non polar streamline and the polar axis, we have extended to the Kerr metric the simple criterion for the magnetic collimation of jets developed by Sauty et al. (1999). We show that the black hole rotation induces a more efficient magnetic collimation of the jet.

scholarly journals Linear and circular polarization of a 1D relativistic jet model

2019 ◽  
Vol 623 ◽  
pp. A152 ◽  
Author(s):  
M. Mościbrodzka
Keyword(s):  
Black Hole ◽  
Three Dimensional ◽  
Compact Objects ◽  
Slab Geometry ◽  
Relativistic Jet ◽  
General Relativistic ◽  
Low Dimensional ◽  
Polarization Models ◽  
Radiative Transfer Equations ◽  
Relativistic Magnetohydrodynamics

Context. Polarimetric observations of black holes allow us to probe structures of magnetic fields and plasmas in strong gravity. Aims. We present a study of the polarimetric properties of a synchrotron spectrum emitted from a relativistic jet using a low-dimensional model. Methods. A novel numerical scheme is used to integrate relativistic polarized radiative transfer equations in a slab geometry where the plasma conditions change along the integration path. Results. We find that the simple model of a non-uniform jet can recover basic observational characteristics of some astrophysical sources with a relativistic jet, such as extremely high rotation measures. Our models incorporate a time-dependent component. A small fluctuation in density or temperature of the plasma along the jet produces significant amounts of fluctuations not only in the fractional linear and circular polarizations, but also in the jet internal rotation measures. Conclusions. The low-dimensional models presented here are developed within the same computational framework as the complex three-dimensional general relativistic magnetohydrodynamics simulations of black hole disks and jets, and they offer guidance when interpreting the results from more complex polarization models. The models presented here are scalable to stationary and transient polarized radio emissions produced by relativistic plasma ejected from around compact objects, in both stellar-mass and supermassive black hole systems.

scholarly journals Wave properties of plasma surrounding the event horizon of a nonrotating black hole

2008 ◽  
Vol 86 (11) ◽  
pp. 1265-1285 ◽  
Author(s):  
M Sharif ◽  
G Mustafa
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Schwarzschild Black Hole ◽  
Magnetohydrodynamics Equations ◽  
Normal Dispersion ◽  
Isothermal Plasma ◽  
General Relativistic ◽  
Relativistic Magnetohydrodynamics ◽  
Wave Properties ◽  
Complex Dispersion

We study the wave properties of a cold isothermal plasma in the vicinity of a Schwarzschild black-hole event horizon. The Fourier-analyzed perturbed 3+1 general relativistic magnetohydrodynamics equations are examined such that the complex dispersion relations are obtained for nonrotating, rotating nonmagnetized, and rotating magnetized backgrounds. The propagation and attenuation vectors along with the refractive index are obtained (shown graphically) to study the dispersive properties of the medium near the event horizon. The results show that no information can be obtained from the Schwarzschild magnetosphere. Further, the pressure stops the existence of normal dispersion of waves.PACS Nos.: 95.30.Sf, 95.30.Qd, 04.30.Nk

scholarly journals Nonradial and nonpolytropic astrophysical outflows

2018 ◽  
Vol 612 ◽  
pp. A63 ◽  
Author(s):  
L. Chantry ◽  
V. Cayatte ◽  
C. Sauty ◽  
N. Vlahakis ◽  
K. Tsinganos
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
High Sensitivity ◽  
Polar Axis ◽  
Kerr Metric ◽  
Efficiency Criterion ◽  
Flux Function ◽  
Available Energy ◽  
Efficiency Parameter ◽  
Field Lines

Context. High-resolution radio imaging of active galactic nuclei (AGN) has revealed that the jets of some sources present superluminal knots and transverse stratification. Recent observational projects, such as ALMA and γ-ray telescopes, such as HESS and HESS2 have provided new observational constraints on the central regions of rotating black holes in AGN, suggesting that there is an inner- or spine-jet surrounded by a disk wind. This relativistic spine-jet is likely to be composed of electron-positron pairs extracting energy from the black hole and will be explored by the future γ-ray telescope CTA. Aims. In this article we present an extension to and generalization of relativistic jets in Kerr metric of the Newtonian meridional self-similar mechanism. We aim at modeling the inner spine-jet of AGN as a relativistic light outflow emerging from a spherical corona surrounding a Kerr black hole and its inner accretion disk. Methods. The model is built by expanding the metric and the forces with colatitude to first order in the magnetic flux function. As a result of the expansion, all colatitudinal variations of the physical quantities are quantified by a unique parameter. Unlike previous models, effects of the light cylinder are not neglected. Results. Solutions with high Lorentz factors are obtained and provide spine-jet models up to the polar axis. As in previous publications, we calculate the magnetic collimation efficiency parameter, which measures the variation of the available energy across the field lines. This collimation efficiency is an integral part of the model, generalizing the classical magnetic rotator efficiency criterion to Kerr metric. We study the variation of the magnetic efficiency and acceleration with the spin of the black hole and show their high sensitivity to this integral. Conclusions. These new solutions model collimated or radial, relativistic or ultra-relativistic outflows in AGN or γ-ray bursts. In particular, we discuss the relevance of our solutions to modeling the M 87 spine-jet. We study the efficiency of the central black hole spin to collimate a spine-jet and show that the jet power is of the same order as that determined by numerical simulations.

scholarly journals Magnetorotational core collapse of possible GRB progenitors – I. Explosion mechanisms

2020 ◽  
Vol 492 (4) ◽  
pp. 4613-4634 ◽  
Author(s):  
M Obergaulinger ◽  
M Á Aloy
Keyword(s):  
Magnetic Fields ◽  
Time Scale ◽  
Main Sequence ◽  
Gamma Ray ◽  
Polar Axis ◽  
Hydrodynamic Instabilities ◽  
Alternative Description ◽  
Ram Pressure ◽  
General Relativistic ◽  
Relativistic Magnetohydrodynamics

ABSTRACT We investigate the explosion of stars with zero-age main-sequence masses between 20 and 35 M⊙ and varying degrees of rotation and magnetic fields including ones commonly considered progenitors of gamma-ray bursts (GRBs). The simulations, combining special relativistic magnetohydrodynamics, a general relativistic approximate gravitational potential, and two-moment neutrino transport, demonstrate the viability of different scenarios for the post-bounce evolution. Having formed a highly massive proto-neutron star (PNS), several models launch successful explosions, either by the standard supernova mechanism based on neutrino heating and hydrodynamic instabilities or by magnetorotational processes. It is, however, quite common for the PNS to collapse to a black hole (BH) within a few seconds. Others might produce proto-magnetar-driven explosions. We explore several ways to describe the different explosion mechanisms. The competition between the time-scales for advection of gas through the gain layer and heating by neutrinos provides an approximate explanation for models with insignificant magnetic fields. The fidelity of this explosion criterion in the case of rapid rotation can be improved by accounting for the strong deviations from spherical symmetry and mixing between pole and equator. We furthermore study an alternative description including the ram pressure of the gas falling through the shock. Magnetically driven explosions tend to arise from a strongly magnetized region around the polar axis. In these cases, the onset of the explosion corresponds to the equality between the advection time-scale and the time-scale for the propagation of Alfvén waves through the gain layer.

scholarly journals Photon boomerang in a nearly extreme Kerr metric

2021 ◽  
Author(s):  
Don N Page
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Opposite Direction ◽  
Elliptic Integral ◽  
Polar Axis ◽  
Rotation Parameter ◽  
Kerr Metric ◽  
Complete Elliptic Integral ◽  
The North ◽  
North Polar

Abstract The Kerr rotating black hole metric has unstable photon orbits that orbit around the hole at fixed values of the Boyer-Lindquist coordinate r that depend on the axial angular momentum of the orbit, as well as on the parameters of the hole. For zero orbital axial angular momentum, these orbits cross the rotational axes at a fixed value of r that depends on the mass M and angular momentum J of the black hole. Nonzero angular momentum of the hole causes the photon orbit to rotate so that its direction when crossing the north polar axis changes from one crossing to the next by an angle I shall call ∆φ, which depends on the black hole dimensionless rotation parameter a/M = cJ/(GM2) by an equation involving a complete elliptic integral of the first kind. When the black hole has a/M ≈ 0.994 341 179 923 26, which is nearly maximally rotating, a photon sent out in a constant-r direction from the north polar axis at r ≈ 2.423 776 210 035 73 GM/c2returns to the north polar axis in precisely the opposite direction (in a frame nonrotating with respect to the distant stars), a photon boomerang.

scholarly journals Leptonic and Hadronic Radiative Processes in Supermassive-Black-Hole Jets

Galaxies ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 72
Author(s):  
Matteo Cerruti
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Polar Axis ◽  
Research Topic ◽  
Relativistic Jets ◽  
Physical Mechanisms ◽  
Radiative Processes ◽  
Radiative Emission ◽  
Supermassive Black Hole ◽  
Active Research

Supermassive black holes lying in the center of galaxies can launch relativistic jets of plasma along their polar axis. The physics of black-hole jets is a very active research topic in astrophysics, owing to the fact that many questions remain open on the physical mechanisms of jet launching, of particle acceleration in the jet, and on the radiative processes. In this work I focus on the last item, and present a review of the current understanding of radiative emission processes in supermassive-black-hole jets.

THE EFFECTS OF DIFFERENT PERTURBATIONS ON THE DYNAMICS OF THE ACCRETION DISK AROUND THE BLACK HOLE

2007 ◽  
Vol 22 (10) ◽  
pp. 1875-1898 ◽  
Author(s):  
ORHAN DÖNMEZ
Keyword(s):  
Shock Wave ◽  
Black Hole ◽  
Shock Waves ◽  
Accretion Disk ◽  
Periodic Oscillation ◽  
Single Star ◽  
Special Cases ◽  
Galactic Black Hole ◽  
General Relativistic ◽  
Armed Spiral

We investigate the special cases of the formation of shocks in the accretion disks around the nonrotating (Schwarzschild) black holes in cases where one or few stars perturb the disk. We model the structure of disk with a 2D fully general relativistic hydrodynamic code and investigate a variety of cases in which the stars interacting with the disk are captured at various locations. We have found the following results: (1) if the stars perturb the disk at nonsymmetric locations, a moving one-armed spiral shock wave is produced and it destroys the disk eventually; (2) if the disk is perturbed by a single star located close to the black hole, a standing shock wave is produced while the disk becomes an accretion tori; (3) if the disk is perturbed by stars at symmetric locations, moving two-armed spiral shock waves are produced while the disk reaches a steady state; (4) continuous injection of matter into the stable disk produces a standing shock wave behind the black hole. Our outcomes reinforce the view that different perturbations on the stable accretion disk carry out different types of shock waves which produce Quasi-Periodic Oscillation (QPO) phenomena in galactic black hole candidates and it is observed as a X-ray.

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