VITA Research: Accretion Disks



Accretion Disk
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:

Other Disk Papers


Other recent papers on accretion disks by VITA members include: VITA Accretion Disk research is sponsored in part by grants from the National Science Foundation, and from NASA.