Modelling MHD accretion-ejection - from the launching area to propagation scales

Abstract

We present results of axisymmetric magnetohydrodynamic (MHD) 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 {\em spherical} coordinates for the numerical grid, implying substantial benefits concerning the numerical resolution and the stability of the simulation. Thanks 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 {\em actual} disk magnetization and not so much the initial magnetization which describes the disk-jet evolution best. Considering the actual disk magnetization we also find that simulations starting with different initial magnetization evolve in a similar - typical - way as due to advection and diffusion 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.

22 pages, 25 figures; submitted to ApJ, revised; suggestions welcome

References in corpus (6)

• PLUTO: a Numerical Code for Computational Astrophysics
• Accretion disc viscosity: how big is alpha?
• MHD simulations of jet acceleration from Keplerian accretion disks: the effects of disk resistivity
• High accretion rates in magnetised Keplerian discs mediated by a Parker instability driven dynamo
• Can Protostellar Jets Drive Supersonic Turbulence in Molecular Clouds?
• The Effects of Large-Scale Magnetic Fields on Disk Formation and Evolution

Cited by in corpus (14)

• The Role of Magnetic Fields in Protostellar Outflows and Star Formation
• Rings and gaps produced by variable magnetic disk winds and avalanche accretion streams: I. Axisymmetric resistive MHD simulations
• rHARM: Accretion and Ejection in Resistive GR-MHD
• Modelling MHD accretion-ejection - episodic ejections of jets triggered by a mean-field disk dynamo
• A Search for Consistent Jet and Disk Rotation Signatures in RY Tau
• Global axisymmetric simulations of photoevaporation and magnetically driven protoplanetary disk winds
• A Study of Outflows in Luminous Quasars at Redshift $\sim 0.4-0.8$
• Dust entrainment in magnetically and thermally driven disk winds
• MHD accretion-ejection: jets launched by a non-isotropic accretion disk dynamo. II. A dynamo tensor defined by the disk Coriolis number
• MHD accretion-ejection: jets launched by a non-isotropic accretion disk dynamo. I. Validation and application of selected dynamo tensorial components
• MHD simulations of the formation and propagation of protostellar jets to observational length scales
• The physics of the MHD disk-jet transition in binary systems: jetted spiral walls launched from disk spiral arms
• Disk Wind Feedback from High-mass Protostars. II. The Evolutionary Sequence
• Helical and nonhelical large-scale dynamos in thin accretion discs