Abstract
We consider accretion disks around black holes at high luminosity, and the problem of the formation of a large-scale magnetic field in such disks, taking into account the non-uniform vertical structure of the disk. The structure of advective accretion disks is investigated, and conditions for the formation of optically thin regions in central parts of the accretion disk are found. The high electrical conductivity of the outer layers of the disk prevents outward diffusion of the magnetic field. This implies a stationary state with a strong magnetic field in the inner parts of the accretion disk close to the black hole, and zero radial velocity at the surface of the disk. The problem of jet collimation by magneto-torsion oscillations is investigated.
Highlights
Quasars and AGN contain supermassive black holes, about 10 HMXR contain stellar mass black holes – microquasars
Jets are observed in objects with black holes: collimated ejection from accretion disks
It was shown by Artemova et al [1], that for large accretion rates there are no local solutions that are continuous over the entire region of existence of the disk and undergo Kepler rotation
Summary
Quasars and AGN contain supermassive black holes, about 10 HMXR contain stellar mass black holes – microquasars. To solve the more general problem, advection and a radial pressure gradient have been included in the analysis of the disk structure by Paczynski & Bisnovatyi-Kogan [19] It was shown by Artemova et al [1], that for large accretion rates there are no local solutions that are continuous over the entire region of existence of the disk and undergo Kepler rotation. Analytic models of the field advection and diffusion in a turbulent disk suggested, that the large-scale field diffuses outward rapidly [15, 17], and prevents a significant amplification of the external poloidal field. This has led to the suggestion that special conditions (non-axisymmetry) are required for the field to be advected inward [21]. This leads to a strong magnetic field in the inner parts of accretion disks
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