2007/11/28 by Igor V. Igumenshchev, I. V. Igumenshchev · 5 citations
Physics and Astronomy · #Accretion (finance) #Angular momentum #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Classical mechanics #Intermediate polar #Magnetic field #Magnetohydrodynamics #Physics #Poynting vector #Stars #White dwarf #astro-ph
paper · pdf · doi:10.1086/529025
23 pages, 10 figures, attached as jpg-files
arxiv created 2007/11/28 · openalex publication_date 2008/04/04 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
The dynamics and structure of accretion disks, which accumulate a vertical magnetic field in their centers, are investigated using two- and three-dimensional MHD simulations. The central field can be built up to the equipartition level, where it disrupts a nearly axisymmetric outer accretion disk inside a magnetospheric radius, forming a magnetically arrested disk (MAD). In the MAD, the mass accretes in the form of irregular dense spiral streams, and the vertical field, split into separate bundles, penetrates through the disk plane in low-density magnetic islands. The accreting mass, when spiraling inward, drags the field and twists it around the axis of rotation, resulting in collimated Poynting jets in the polar directions. These jets are powered by the accretion flow with an efficiency of up to ~1.5% (in units of in c 2 ). The spiral flow pattern in the MAD is dominated by modes with low azimuthal wavenumbers m ∼ 1–5 and can be a source of quasi-periodic oscillations in the outgoing radiation. The formation of the MAD and the Poynting jets can naturally explain the observed changes of spectral states in galactic black hole binaries. Our study is focused on black hole accretion flows; however, the results can also be applied to accretion disks around nonrelativistic objects, such as young stellar objects and stars in binary systems.