Modeling MHD accretion-ejection—from the launching area to propagation scales

Journal Article · Sat Sep 20 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/793/1/31· OSTI ID:22365032

Stepanovs, Deniss; Fendt, Christian ^[1]

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1. Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

We present the results of axisymmetric magnetohydrodynamic simulations investigating the launching of jets and outflows from a magnetically diffusive accretion disk. The time evolution of the disk structure is self-consistently taken into account. In contrast to previous works, we have applied spherical coordinates for the numerical grid, implying substantial benefits concerning the numerical resolution and the stability of the simulation. Due to the new setup, we were able to run simulations for more than 150,000 dynamical times on a domain extending 1500 inner disk radii with a resolution of up to 24 cells per disk height in the inner disk. Depending on the disk magnetization, jet launching occurs in two different but complementary regimes—jets driven predominantly by centrifugal or magnetic forces. These regimes differ in the ejection efficiency concerning mass, energy, and angular momentum. We show that it is the actual disk magnetization and not so much the initial magnetization that best describes the disk-jet evolution. Considering the actual disk magnetization, we also find that simulations starting with different initial magnetization evolve in a similar—typical—way, due to advection and diffusion, as the magnetic flux in the disk evolves in time. Exploring a new, modified diffusivity model, we confirm the self-similar structure of the global jet-launching disk, obtaining power laws for the radial profiles of the disk physical variables such as density, magnetic field strength, or accretion velocity.

• OSTI ID: 22365032
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 793; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ADVECTION
ANGULAR MOMENTUM
AXIAL SYMMETRY
COMPUTERIZED SIMULATION
DENSITY
DIFFUSION
EFFICIENCY
GALAXIES
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETIZATION
MAGNETOHYDRODYNAMICS
RESOLUTION
SPHERICAL CONFIGURATION
STABILITY
STAR EVOLUTION
STARS
STELLAR WINDS