1989 Fiscal Year Final Research Report Summary
Magnetohydrodynamical Structure in the Vicinity of a Black Hole
| Project/Area Number |
62540176
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Astronomy
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| Research Institution | Ibaraki University |
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Principal Investigator |
YOKOSAWA Masayoshi Ibaraki University, Faculty of Science Assistant Professor, 理学部, 助教授 (30158357)
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| Project Period (FY) |
1987 – 1989
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| Keywords | Active Galaxy / Black Hole / Energy Extraction / Magnetohydrodynamics |
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| Research Abstract |
1. Extraction process of black holes spin energy and magnetohydrodynamical structure around a Kerr black hole are studied by an exact nonstationary solution for the variation of magnetic field with a given axially symmetric accretion. Initially homogeneous magnetic field lines are twisted by the frame-dragging effect, thus exerting a torque on a infalling plasma. This hydromagnetic extraction of a black holes spin energy is analyzed on the assumption of equipartition between the magnetic and kinetic energies of a falling plasma. In order to examine the possible structure of the magnetic field formed around the hole we investigate precisely the structure of the nonstationary magnetic field produced by the stationary accretion. The strongly winding field is formed around the event horizon and then the horizon is seen as wrapped by a bundle of magnetic field lines. The evolution of a rotating black hole immersed in a magnetized plasma and electric energy generation caused by the interaction of magnetized infalling plasma with the accretion disk are discussed.
2. In order to make clear the focusing of the energy and momentum by wave motion, the wave propagation of a sound wave were investigated in curved space-time. By using a canonical-type formulation for the hydrodynamical disturbances in accretion disk, the basic properties of sound wave propagation and the numerical calculations of motion of the locus of simultaneous fronts of wave packets were preseted. The sound waves inside the potentials hi-11 converge into the rotation axis of the black hole.
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