Abstract
We explore the analogy with pulsars and investigate the structure of the force-free magnetosphere around a Kerr black hole. We propose that the source of the black hole magnetic field is the Poynting-Robertson effect on the plasma electrons at the inner edge of the surrounding accretion disk, the so called Cosmic Battery. The magnetospheric solution is characterized by the distributions of the magnetic field angular velocity and the poloidal electric current. These are not arbitrary. They are determined self-consistently by requiring that magnetic field lines cross smoothly the two singular surfaces of the problem, the inner ‘light surface’ located inside the ergosphere, and the outer ‘light surface’ which is the generalization of the pulsar light cylinder. The black hole forms a relativistic jet only if it is surrounded by a thick disk and/or extended disk outflows.
Highlights
We explore the analogy with pulsars and investigate the structure of the force-free magnetosphere around a Kerr black hole
The electromagnetic extraction of energy from a spinning black hole can be one of the most powerful and efficient engines in the Universe. [2] first argued that a spinning black hole threaded by a sufficiently strong magnetic field and permeated by an electron-positron plasma generated from pair cascades establishes a force-free magnetosphere, in direct analogy to the theory of ‘pulsar electrodynamics’ developed a few years earlier by [15]. [21] realized that many astrophysicists feel uncomfortable in curved spacetime and rewrote black hole electrodynamics in an absolute-space/universal-time formulation with the hope that it may catalyze pulsar-experienced astrophysicists to begin research in black hole electrodynamics and to bring to bear on this topic their lore about the axisymmetric pulsar problem
Before we proceed with a numerical solution for the black hole magnetosphere, we would like to discuss what is the origin of the black hole magnetic field
Summary
The electromagnetic extraction of energy from a spinning black hole can be one of the most powerful and efficient engines in the Universe. [2] first argued that a spinning black hole threaded by a sufficiently strong magnetic field and permeated by an electron-positron plasma generated from pair cascades establishes a force-free magnetosphere, in direct analogy to the theory of ‘pulsar electrodynamics’ developed a few years earlier by [15]. [21] realized that many astrophysicists feel uncomfortable in curved spacetime (sic) and rewrote black hole electrodynamics in an absolute-space/universal-time formulation with the hope that it may catalyze pulsar-experienced astrophysicists to begin research in black hole electrodynamics and to bring to bear on this topic their lore about the axisymmetric pulsar problem (sic). 4pm: A central element of the magnetosphere is the poloidal current sheet that takes care of magnetospheric current closure It extends from the tip of the closed line region on the light cylinder to infinity, and from the tip to the surface of the star along the separatrix between closed and open field lines. The field lines isorotation law applies in ideal black hole magnetospheres too, and a generalized light cylinder still forms 6bh: The black hole is expected to lose energy at a rate proportional to the square of the total amount of open magnetic flux and to the square of the field line rotation angular velocity. Before we proceed with a numerical solution for the black hole magnetosphere, we would like to discuss what is the origin of the black hole magnetic field
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