Journal Article

Accreting magnetofluids around a rotating compact object with a dipolar magnetic field

M. Shaghaghian

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 1, pages 534-544
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18727.x
Accreting magnetofluids around a rotating compact object with a dipolar magnetic field

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The dynamics of an axisymmetric stationary disc of accreting magnetofluid with finite conductivity around a rotating compact object is presented here. Along with the Maxwell equations and the generalized Ohm law, the basic equations governing the motion of a finitely conducting plasma in a curved space–time around a slowly rotating compact object are derived. The finite electrical conductivity is taken into account for the plasma; however, the shear viscous stress is neglected, as well as the self-gravity of the disc. In this case, energy dissipation occurs only through the finite resistivity. The magnetic stress takes the place of viscous stress in the standard disc model, and extracts angular momentum from the disc. The accreting plasma in the presence of an external dipole magnetic field gives rise to a current in the azimuthal direction. The azimuthal current produced as a result of the motion of the magnetofluid generates the magnetic field for the disc. Magnetic lines of force can penetrate the accretion disc because of the presence of finite resistivity. It has been shown that the dipolar magnetic field structure of the central black hole is modified inside the disc. In fact, the magnetic field lines are pushed outward and are continuous across the disc boundary. It has been demonstrated that the inward flow passing through a sub-Alfvénic region becomes super-Alfvénic to fall into the event horizon.

Keywords: accretion, accretion discs; MHD; relatavistic processes

Journal Article.  4977 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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