Magnetically Arrested Disks and the Origin of Poynting Jets: A Numerical Study

Journal Article · Fri Apr 04 04:00:00 EDT 2008 · The Astrophysical Journal

DOI:https://doi.org/10.1086/529025· OSTI ID:926631

Igumenshchev, I V ^[1]

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1. Laboratory for Laser Energetics, University of Rochester, Rochester, NY

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 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 wuth an efficiency of up to ~1.5% (in units of Msub-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 oscillatiosn 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.

• Research Organization: Laboratory for Laser Energetics, University of Rochester
• Sponsoring Organization: USDOE
• DOE Contract Number: FC52-08NA28302
• OSTI ID: 926631
• Report Number(s): DOE/NA/28302-813; 2007-168; 1783
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Vol. 677
• Country of Publication: United States
• Language: English

Related Subjects

ISM: jets and outflows
MHD
accrestion
accretion disks
black hole physics
galaxies: jets
gamma rays: bursts
instabilities
magnetic fields
stars: oscillations
turbulence