Oblique Magnetic Fields and the Role of Frame Dragging Near Rotating Black Hole

Karas, Vladimír; Kopáček, Ondřej; Kunneriath, D.

doi:10.14311/ap.2014.54.0398

Cited by 12 publications

(11 citation statements)

References 60 publications

(92 reference statements)

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“…Previously, we have demonstrated that the structure of the electromagnetic field is strongly influenced by the relativistic effects of a spinning compact object (Karas & Kopáček 2009;Karas et al 2014Karas et al , 2012. In particular, we have shown that close to the event horizon, where the frame dragging dominates, these effects shape the field lines (described by the vacuum solution of Maxwell's equations) in a way that may mimic the behavior typically associated with magnetohydrodynamic plasma.…”

Section: Introductionmentioning

confidence: 76%

Near-horizon Structure of Escape Zones of Electrically Charged Particles around Weakly Magnetized Rotating Black Hole

Kopáček

Karas

2018

ApJ

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An interplay of magnetic fields and gravitation drives accretion and outflows near black holes. However, a specific mechanism is still a matter of debate; it is very likely that different processes dominate under various conditions. In particular, for the acceleration of particles and their collimation in jets, an ordered component of the magnetic field seems to be essential. Here we discuss the role of largescale magnetic fields in transporting the charged particles and dust grains from the bound orbits in the equatorial plane of a rotating (Kerr) black hole and the resulting acceleration along trajectories escaping the system in a direction parallel to the symmetry axis (perpendicular to the accretion disk). We consider a specific scenario of destabilization of circular geodesics of initially neutral matter by charging (e.g., due to photoionization). Some particles may be set on escaping trajectories and attain relativistic velocity. The case of charged particles differs from charged dust grains by their charge-tomass ratio, but the acceleration mechanism operates in a similar manner. It appears that the chaotic dynamics controls the outflow and supports the formation of near-horizon escape zones. We employ the technique of recurrence plots to characterize the onset of chaos in the outflowing medium. We investigate the system numerically and construct the basin-boundary plots, which show the location and the extent of the escape zones. The effects of black hole spin and magnetic field strength on the formation and location of escape zones are discussed, and the maximal escape velocity is computed.

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Section: Introductionmentioning

confidence: 76%

Near-horizon Structure of Escape Zones of Electrically Charged Particles around Weakly Magnetized Rotating Black Hole

Kopáček

Karas

2018

ApJ

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“…The combined effects of nonaxisymmetry and rotation on the structure of vacuum electromagnetic fields near compact objects has already been investigated by many authors; for the analyses especially close to our context, see Kopáček et al (2018) and Karas et al (2013Karas et al ( , 2014. As a consequence of profound changes in the topology of the field induced by breaking the axial symmetry, the dynamics of charged particles also changes dramatically and generally becomes more prone to deterministic chaos.…”

Section: Introductionmentioning

confidence: 86%

Near-horizon structure of escape zones of electrically charged particles around weakly magnetized rotating black hole. II. Acceleration and escape in the oblique magnetosphere

Kopáček¹,

Karas²

2020

Preprint

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Strong gravity and magnetic fields are key ingredients that power processes of accretion and ejection near compact objects. While the particular mechanisms that operate here are still discussed, it seems that the presence of an ordered magnetic field is crucial for the acceleration and collimation of relativistic jets of electrically charged particles on superhorizon length scales. In this context, we further study the effect of a large-scale magnetic field on the dynamics of charged particles near a rotating black hole. We consider a scenario in which the initially neutral particles on regular geodesic orbits in the equatorial plane are destabilized by a charging process (e.g., by photoionization). Some charged particles are accelerated out of the equatorial plane, and they follow jetlike trajectories with relativistic velocities. In our previous paper, we investigated this scenario for the case of perfect alignment of the magnetic field with the axis of rotation; i.e., the system was considered axisymmetric. Here we relax this assumption and investigate nonaxisymmetric systems in which the magnetic field is arbitrarily inclined with respect to the black hole spin. We study the system numerically in order to locate the zones of escaping trajectories and compute the maximum (terminal) escape velocity. It appears that breaking the axial symmetry (even by small inclination angles) substantially increases the fraction of escaping orbits and allows the acceleration to ultrarelativistic velocities that were excluded in the axisymmetric setup. The presence of transient chaotic dynamics in the launching region of the relativistic outflow is confirmed with chaotic indicators.

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“…We have numerically located the NPs for different values of χ and discussed their location as a function of coordinate time t and radius of the conductor R. We conclude that NPs only form for some period of coordinate time t and that they are always located outside the conducting region of a magnetic star. Previously, we have also studied the formation of magnetic NPs in the curved spacetime of a rotating Kerr black hole [2,3,23]. Namely, we investigated the nearhorizon structure of an asymptotically uniform magnetic field (aligned or inclined with respect to the axis of rotation).…”

Section: Conclusion and Final Remarksmentioning

confidence: 99%

Null points in the magnetosphere of a plunging neutron star

Kopáček¹,

Tahamtan²,

Karas³

2018

Phys. Rev. D

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We explore the structure of a dipole-type vacuum field of a slowly rotating magnetic star near the horizon of a supermassive black hole, where the structure of field lines becomes highly distorted by effects of strong gravity. Such a situation may occur near a neutron star in the final stages of a plunging trajectory into a galactic center. We solve Maxwell's equations in the Rindler approximation for the rotating conducting source of dipolar magnetic field arbitrarily inclined with respect to the axis of rotation. For the fixed inclination angle we calculate the field including the radiative terms while in the general case we discuss the electromagnetic field considering the near-field terms only. In the latter case we investigate the emergence of magnetic null points within the vacuum magnetosphere. Null points become highly relevant in the presence of astrophysical plasma where they are connected with processes of magnetic reconnection and mass ejection.

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Oblique Magnetic Fields and the Role of Frame Dragging Near Rotating Black Hole

Cited by 12 publications

References 60 publications

Near-horizon Structure of Escape Zones of Electrically Charged Particles around Weakly Magnetized Rotating Black Hole

Near-horizon Structure of Escape Zones of Electrically Charged Particles around Weakly Magnetized Rotating Black Hole

Near-horizon structure of escape zones of electrically charged particles around weakly magnetized rotating black hole. II. Acceleration and escape in the oblique magnetosphere

Null points in the magnetosphere of a plunging neutron star

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