VITA Research: Accretion Disks

Several members of VITA work on accretion disks and related phenomena. John Hawley is investigating the magnetohydrodynamics of accretion disks. Working with Steve Balbus, he has been carrying out computer simulations of magnetohydrodynamical turbulence in disks and the angular momentum transport that results. Disk turbulence arises from the presence of a weak magnetic field instability in accretion disks (see S. A. Balbus and J. F. Hawley, A Powerful Local Shear Instability in Weakly Magnetized Disks 1991, ApJ 376, 214).

Zhi-Yun Li’s research concerns protostellar disks and magnetohydrodynamic winds from disk systems.

Phil Arras works on quasi-periodic oscillations from accretions disks in black hole binaries (seismology of accretion tori and wave excitation by MHD turbulence.

Balbus & Hawley Instability

These numerical simulations demonstrate the Balbus & Hawley Instability. The first images show the initial and final states of a shearing box (a part of an accretion disk with negligible curvature) using hydrodynamics only. The initial velocity instabilities disappear after a number of orbits. The second pair of images shows the initial and final states of a shearing box using magnetohydrodynamic code. In this case, the instability persists after the same number of orbits.

		256x246x256 shearing box, hydro only Movies: MPEG (3.8 MB) or QuickTime (5.5 MB)
		64x64x128 shearing box, magnetic field and hydro Movies: MPEG (2.5 MB) or QuickTime (3.4 MB)

Disk Simulation Papers on the Web

Here are recent papers on global accretion disk simulations which include various MPEG animations:

J-P. De Villiers, J.F. Hawley, & J.H. Krolik Astrophysical Journal, 599, 1238 (2003). See Magnetically Driven Accretion Flows in the Kerr Metric. I. Models and Overall Structure for high-res figures and movies and PDF file.
J-P. De Villiers & J.F. Hawley Astrophysical Journal, 592, 1060 (2003). See Global General Relativistic Magnetohydrodynamic Simulations of Accretion Tori for high-res figures and movies and PDF file.
Jean-Pierre de Villiers & John F. Hawley, A Numerical Method for General Relativistic Magnetohydrodynamics Astrophysical Journal , 589, 458 (2003).
John F. Hawley & Julian H. Krolik, High Resolution Simulations of the Plunging Region in a Pseudo-Newtonian Potential: Dependence on Numerical Resolution and Field Topology Astrophysical Journal, 566, 164 (2002). The web version of this paper also provides MPEG animations.
John F. Hawley & Steven A. Balbus, The Dynamical Structure of Nonradiative Black Hole Accretion Flows Astrophysical Journal , 573, 738 (2002)
Jean-Pierre de Villiers & John F. Hawley, Three-Dimensional Hydrodynamic Simulations of Accretion Tori in Kerr Spacetimes, Astrophysical Journal , 577, 866 (2002).
John F. Hawley, Steven A. Balbus, & James M. Stone, A Magnetohydrodynamic Nonradiative Accretion Flow in Three Dimensions Astrophysical Journal Letters, 554, (2001) The preprint is on the web along with a MPEG animations, and a color version of figure 1.
John F. Hawley, Global MHD Simulations of Cylindrical Keplerian Disks. Astrophysical Journal, 554, 534 (2001). The preprint is on the web along with MPEG animations of the simulations.
John F. Hawley & Julian H. Krolik, Global MHD Simulation of the Inner Accretion Disk in a Pseudo-Newtonian Potential. Astrophysical Journal, 548, 348 (2001). The web version of this paper includes MPEG animations of the simulation.
John F. Hawley, Global Magnetohydrodynamical Simulations of Accretion Tori Astrophysical Journal, 528, 462 (2000). The web version of this paper also provides MPEG animations.

Other Disk Papers

Other recent papers on accretion disks by VITA members include:

Balbus, S. A. and J. F. Hawley, Instability, Turbulence, and Enhanced Transport in Accretion Disks 1998, Reviews of Modern Physics, 70, 1
Stone, J. M., Hawley, J.F., Gammie, C.F., and Balbus, S.A., Three-Dimensional Magnetohydrodynamical Simulations of Vertically Stratified Accretion Disks 1996, ApJ, 463, 656
Hawley, J. F., Gammie, C.F., and Balbus, S.A., Local Three Dimensional Simulations of an Accretion Disk Dynamo 1996, ApJ, 464, 690
Balbus, S.A., Hawley, J.F., and Stone, J.M., Nonlinear Stability, Hydrodynamic Turbulence, and Transport in Disks 1996, ApJ, 467, 76
Hawley, J. F. Keplerian Complexity: Numerical Simulations of Accretion Disk Transport 1995, Science, 269, 1365
Balbus, S. A. General Local Stability Criteria for Stratified Weakly Magnetized Rotating Systems, 1995, ApJ, 453, 380
Zhi-Yun Li, Self-similar Collapse of Magnetized Molecular Cloud Cores with Ambipolar Diffusion and the "Magnetic Flux Problem" in Star Formation 1998, ApJ, 497, 850
Zhi-Yun Li, Formation and Collapse of Magnetized Spherical Molecular Cloud Cores 1998, ApJ, 493, 230
Zhi-Yun Li and F. H. Shu Self-similar Collapse of an Isopedic Isothermal Disk 1997, ApJ, 475, 237
Zhi-Yun Li, Magnetohydrodynamic disk-wind connection: Self-similar solutions 1995, ApJ, 444, 848

VITA Accretion Disk research is sponsored in part by grants from the National Science Foundation, and from NASA.