scholarly journals High-energy collision of particles in the magnetic field far from black holes

2014 ◽  
Vol 29 (29) ◽  
pp. 1450151
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Center Of Mass ◽  
High Energy ◽  
Axially Symmetric ◽  
High Energy Collision ◽  
Mass Frame ◽  
Symmetric Black Hole ◽  
Rotating Star ◽  
The Magnetic Field

We consider collision of two particles in the axially symmetric black hole metric in the magnetic field. If the value of the angular momentum |L| of one particles grows unbound (but its Killing energy remains fixed) one can achieve unbound energy in the center-of-mass frame E c.m. In the absence of the magnetic field, collision of this kind is known to happen in the ergoregion. However, if the magnetic field strength B is also large, with the ratio |L|/B being finite, large E c.m. can be achieved even far from a black hole, in the almost flat region. Such an effect also occurs in the metric of a rotating star.

scholarly journals Kinematics of ultra-high energy particle collisions near black holes in the magnetic field

2015 ◽  
Vol 30 (06) ◽  
pp. 1550027 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Center Of Mass ◽  
High Energy ◽  
High Energy Particle ◽  
Ultra High Energy ◽  
Particle Collisions ◽  
Mass Frame ◽  
Bsw Effect ◽  
The Magnetic Field

There are different versions of collisions of two particles near black holes with unbound energy E cm in the center of mass frame. The so-called BSW effect arises when a slow fine-tuned "critical" particle hits a rapid "usual" one. We discuss a scenario of collision in the strong magnetic field for which explanation turns out to be different. Both particles are rapid but the nonzero angle between their velocities (which are both close to c, the speed of light) results in a relative velocity close to c and, hence, big E cm .

scholarly journals High energy particle collisions and geometry of horizon

2016 ◽  
Vol 25 (10) ◽  
pp. 1650095 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Black Hole ◽  
Center Of Mass ◽  
Naked Singularity ◽  
High Energy ◽  
Fine Tuning ◽  
High Energy Particle ◽  
Axially Symmetric ◽  
Particle Collisions ◽  
Material Source ◽  
Mass Frame

We consider collision of two geodesic particles near the lightlike surface (black hole horizon or naked singularity) of such an axially symmetric rotating or static metric that the coefficient [Formula: see text] on this surface. It is shown that the energy in the center of mass frame [Formula: see text] is indefinitely large even without fine-tuning of particles’ parameters. Kinematically, this is the collision between two rapid particles that approach the horizon almost with the speed of light but at different angles (or they align along the normal to the horizon too slowly). The latter is the reason why the relative velocity tends to that of light, hence to high [Formula: see text]. Our approach is model-independent. It relies on general properties of geometry and is insensitive to the details of material source that supports the geometries of the type under consideration. For several particular models (the stringy black hole, the Brans–Dicke analogue of the Schwarzschild metric and the Janis–Newman–Winicour one) we recover the results found in literature previously.

scholarly journals Very High-Energy Emission from the Direct Vicinity of Rapidly Rotating Black Holes

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 122 ◽  
Author(s):  
Kouichi Hirotani
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Black Hole ◽  
Electric Field ◽  
Gamma Rays ◽  
Accretion Rate ◽  
High Energy ◽  
Relativistic Electrons ◽  
Field Lines ◽  
The Magnetic Field

When a black hole accretes plasmas at very low accretion rate, an advection-dominated accretion flow (ADAF) is formed. In an ADAF, relativistic electrons emit soft gamma-rays via Bremsstrahlung. Some MeV photons collide with each other to materialize as electron-positron pairs in the magnetosphere. Such pairs efficiently screen the electric field along the magnetic field lines, when the accretion rate is typically greater than 0.03–0.3% of the Eddington rate. However, when the accretion rate becomes smaller than this value, the number density of the created pairs becomes less than the rotationally induced Goldreich–Julian density. In such a charge-starved magnetosphere, an electric field arises along the magnetic field lines to accelerate charged leptons into ultra-relativistic energies, leading to an efficient TeV emission via an inverse-Compton (IC) process, spending a portion of the extracted hole’s rotational energy. In this review, we summarize the stationary lepton accelerator models in black hole magnetospheres. We apply the model to super-massive black holes and demonstrate that nearby low-luminosity active galactic nuclei are capable of emitting detectable gamma-rays between 0.1 and 30 TeV with the Cherenkov Telescope Array.

scholarly journals Generation of Magnetic Fields in Accreting Systems as a Basis of Nonthermal Mode of Energy Release

1993 ◽  
Vol 157 ◽  
pp. 197-201
Author(s):  
L.A. Pustil'Nik ◽  
N.R. Ikhsanov
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Magnetic Fields ◽  
Energy Release ◽  
Polar Region ◽  
High Energy ◽  
Ultra High Energy ◽  
The Magnetic Field

Generation of the magnetic field during procces of disc accretion onto black hole or magnetize neutrin star may form current structures in a polar region. The instability and disruption of this currents must lead to effective acceleration of the particles to ultra high energy as it observe by GRO and UHE-astronomy experiments.

ACCELERATION OF PARTICLES AS A UNIVERSAL PROPERTY OF ERGOSPHERE

2013 ◽  
Vol 28 (11) ◽  
pp. 1350037 ◽  
Author(s):  
O. B. ZASLAVSKII
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Recent Observation ◽  
Center Of Mass ◽  
Kerr Black Hole ◽  
Acceleration Of Particles ◽  
Axially Symmetric ◽  
Fixed Energy ◽  
Mass Frame

We show that recent observation made by Grib and Pavlov, [A. A. Grib and Yu. V. Pavlov, Europhys. Lett.101, 20004 (2013)] for the Kerr black hole is valid in the general case of rotating axially symmetric metric. Namely, collision of two particles in the ergosphere leads to indefinite growth of the energy in the center-of-mass frame, provided the angular momentum of one of the two particles is negative and increases without limit for a fixed energy at infinity. General approach enabled us to elucidate why the role of the ergosphere is crucial in this process.

scholarly journals Black hole with a scalar field as a particle accelerator

2017 ◽  
Vol 26 (10) ◽  
pp. 1750108 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Center Of Mass ◽  
High Energy ◽  
Particle Accelerator ◽  
Particle Collision ◽  
Axially Symmetric ◽  
Speed Of Light ◽  
Test Particles ◽  
Energy Formula

We consider stationary axially symmetric black holes with the background scalar field and test particles that can interact with this field directly. Then, particle collision near a black hole can lead to the unbounded energy [Formula: see text] in the center of mass frame (contrary to some recent claims in literature). This happens always if one of the particles is neutral whereas another one has nonzero scalar charge. Kinematically, two cases occur here. (i) A neutral particle approaches the horizon with the speed of light while the velocity of the charged one remains separated from it (this is direct analogue of the situation with collision of geodesic particles.). (ii) Both particles approach the horizon with the speed almost equal to that of light but with different rates. As a result, in both cases the relative velocity also approaches the speed of light, so that [Formula: see text] becomes unbounded. We consider also a case when the metric coefficient [Formula: see text] near a black hole. Then, overlap between the geometric factor and the presence of the scalar field opens additional scenarios in which unbounded energy [Formula: see text] is possible as well. We give a full list of possible scenarios of high-energy collisions for the situations considered.

scholarly journals High-energy collisions inside black holes and their counterpart in flat spacetime

2014 ◽  
Vol 23 (05) ◽  
pp. 1450045 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Black Hole ◽  
Center Of Mass ◽  
High Energy ◽  
General Character ◽  
Particle Collisions ◽  
Flat Spacetime ◽  
Mass Frame ◽  
High Energy Collisions ◽  
Horizon Geometry

Two particles can collide inside a nonextremal black hole in such a way that the energy E c.m. in their center-of-mass frame becomes as large as one likes. We show that this effect can be understood with the help of a simple analogy with particle collisions in flat spacetime. As the two-dimensional part of near-horizon geometry inside a black hole is described by the flat Milne metric, the results have a general character. Full classification of scenarios with unbound E c.m. is suggested. Some scenarios of this kind require proximity of collision to the bifurcation point, but for some other ones this is not necessary.

scholarly journals Ultrahigh energy particle collisions near the black hole horizon in the strong magnetic field

2014 ◽  
Vol 29 (21) ◽  
pp. 1450112 ◽  
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Strong Magnetic Field ◽  
Center Of Mass ◽  
Black Hole Horizon ◽  
Ultrahigh Energy ◽  
Particle Collisions ◽  
Energy Particle ◽  
Neutral Particles ◽  
Mass Frame

We consider collision between two charged (or charged and neutral) particles near the black hole horizon in the strong magnetic field B. It is shown that there exists a strip near the horizon within which collision of any two such particles leads to ultrahigh energy in the center-of-mass frame (CM frame). The results apply to generic (not necessarily vacuum) black holes.

scholarly journals Blandford-Znajek mechanism in the general stationary axially-symmetric black-hole spacetime

2021 ◽  
Vol 2021 (12) ◽  
pp. 002
Author(s):  
R.A. Konoplya ◽  
J. Kunz ◽  
A. Zhidenko
Keyword(s):  
Black Hole ◽  
Deformation Parameter ◽  
Rotation Parameter ◽  
Energy Extraction ◽  
Axially Symmetric ◽  
Asymptotically Flat ◽  
Kerr Spacetime ◽  
Black Hole Spacetime ◽  
Symmetric Black Hole ◽  
The Magnetic Field

Abstract We consider the Blandford-Znajek process of electromagnetic extraction of energy from a general axially symmetric asymptotically flat slowly rotating black hole. Using the general parametrization of the black-hole spacetime we construct formulas for the flux of the magnetic field and the rate of energy extraction, which are valid not only for the Kerr spacetime, but also for its arbitrary axially symmetric deformations. We show that in the dominant order these quantities depend only on a single deformation parameter, which relates the spin frequency of a black hole with its rotation parameter.

scholarly journals Broadband Linear Polarization in Ap Stars

1993 ◽  
Vol 138 ◽  
pp. 305-309
Author(s):  
Marco Landolfi ◽  
Egidio Landi Degl’Innocenti ◽  
Maurizio Landi Degl’Innocenti ◽  
Jean-Louis Leroy ◽  
Stefano Bagnulo
Keyword(s):  
Magnetic Field ◽  
Circular Polarization ◽  
Linear Polarization ◽  
Rotation Axis ◽  
Spectral Lines ◽  
Line Of Sight ◽  
Long Time ◽  
Rotating Star ◽  
Ap Stars ◽  
The Magnetic Field

AbstractBroadband linear polarization in the spectra of Ap stars is believed to be due to differential saturation between σ and π Zeeman components in spectral lines. This mechanism has been known for a long time to be the main agent of a similar phenomenon observed in sunspots. Since this phenomenon has been carefully calibrated in the solar case, it can be confidently used to deduce the magnetic field of Ap stars.Given the magnetic configuration of a rotating star, it is possible to deduce the broadband polarization at any phase. Calculations performed for the oblique dipole model show that the resulting polarization diagrams are very sensitive to the values of i (the angle between the rotation axis and the line of sight) and β (the angle between the rotation and magnetic axes). The dependence on i and β is such that the four-fold ambiguity typical of the circular polarization observations ((i,β), (β,i), (π-i,π-β), (π-β,π-i)) can be removed.

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