Existence of the Blandford-Znajek monopole for a slowly rotating Kerr black hole

Grignani, G.; Harmark, Troels; Orselli, Marta

doi:10.1103/physrevd.98.084056

Cited by 18 publications

(39 citation statements)

References 24 publications

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“…This provides independent evidence to the issues discovered with the asymptotics of the Blandford-Znajek (split-)monopole in Ref. [1] from which it follows that its perturbative construction is inconsistent.…”

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confidence: 58%

Force-free electrodynamics near rotation axis of a Kerr black hole

Grignani

Harmark²,

Orselli

2020

Class. Quantum Grav.

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Despite their potential importance for understanding astrophysical jets, physically realistic exact solutions for magnetospheres around Kerr black holes have not been found, even in the force-free approximation. Instead approximate analytical solutions such as the Blandford-Znajek (split-)monopole, as well as numerical solutions, have been constructed. In this paper we consider a new approach to the analysis and construction of such magnetospheres. We consider force-free electrodynamics close to the rotation axis of a magnetosphere surrounding a Kerr black hole assuming axisymmetry. This is the region where the force-free approximation should work the best, and where the jets are located. We perform a systematic study of the asymptotic region with (split-)monopole, paraboloidal and vertical asymptotic behaviors. Imposing asymptotics similar to a (split-)monopole, we find that demanding regularity at the rotation axis and the event horizon restricts solutions of the stream equation so much that it is not possible for a solution to be continuously connected to the static (split-)monopole around the Schwarzschild black hole in the limit where the rotation goes to zero. This provides independent evidence to the issues discovered with the asymptotics of the Blandford-Znajek (split-)monopole in Ref.[1] from which it follows that its perturbative construction is inconsistent.

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confidence: 58%

Force-free electrodynamics near rotation axis of a Kerr black hole

Grignani

Harmark²,

Orselli

2020

Class. Quantum Grav.

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“…In 2018 the authors of Ref. [10] showed that there is a problem already at second order, since the approximate solution is not consistent with the exact stream equation expanded at large r.…”

Section: Perturbation Methodsmentioning

confidence: 99%

Consistent Blandford-Znajek expansion

Armas

Cai

Compère

et al. 2020

J. Cosmol. Astropart. Phys.

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The Blandford-Znajek mechanism is the continuous extraction of energy from a rotating black hole via plasma currents flowing on magnetic field lines threading the horizon. In the discovery paper, Blandford and Znajek demonstrated the mechanism by solving the equations of force-free electrodynamics in a perturbative expansion valid at small black hole spin. Attempts to extend this perturbation analysis to higher order have encountered inconsistencies. We overcome this problem using the method of matched asymptotic expansions, taking care to resolve all of the singular surfaces (light surfaces) in the problem. Working with the monopole field configuration, we show explicitly how the inconsistencies are resolved in this framework and calculate the field configuration to one order higher than previously known. However, there is no correction to the energy extraction rate at this order. These results confirm the basic consistency of the split monopole at small spin and lay a foundation for further perturbative studies of the Blandford-Znajek mechanism. * j.armas@uva.nl †

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“…in active galactic nuclei and quasars. For more recent discussions on the consistency of the BZ mechanism, see [2][3][4].…”

Section: Jhep12(2020)018mentioning

confidence: 99%

Electro-magnetic energy extraction from rotating black holes in AdS

Callebaut

Rodríguez

Verlinde

2020

J. High Energ. Phys.

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Force-Free Electrodynamics for black holes in Anti de Sitter is considered. We present new, energy extracting solutions of Force-Free Electrodynamics in Anti de Sitter-Near Horizon Extremal Kerr and Super-Entropic Near Horizon Extremal Kerr geometries. The relevant equations of motion are derived from an action for force-free plasma surrounding spinning black holes with generic asymptotics. We consider the energy flux of electrodynamic fields in rotating frames to argue that the correct measure for energy extraction is the energy flux measured by a rotating observer in the near horizon region. We illustrate this procedure by application to near horizon solutions in Kerr, AdS-Kerr and BTZ.

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Existence of the Blandford-Znajek monopole for a slowly rotating Kerr black hole

Cited by 18 publications

References 24 publications

Force-free electrodynamics near rotation axis of a Kerr black hole

Force-free electrodynamics near rotation axis of a Kerr black hole

Consistent Blandford-Znajek expansion

Electro-magnetic energy extraction from rotating black holes in AdS

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