Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-01-28
Astrophys.J. 634 (2005) 1353-1371
Astronomy and Astrophysics
Astrophysics
Accepted for publication in ApJ. An additional MPEG movie can be downloaded at http://www.mpia.de/homes/johansen/
Scientific paper
10.1086/497118
We measure the turbulent diffusion coefficient of dust grains embedded in magnetorotational turbulence in a protoplanetary disc directly from numerical simulations and compare it to the turbulent viscosity of the flow. The simulations are done in a local coordinate frame comoving with the gas in Keplerian rotation. Periodic boundary conditions are used in all directions, and vertical gravity is not applied to the gas. Using a two-fluid approach, small dust grains of various sizes (with friction times up to $\varOmega_0 \tau_{\rm f}=0.02$) are allowed to move under the influence of friction with the turbulent gas. We measure the turbulent diffusion coefficient of the dust grains by applying an external sinusoidal force field acting in the vertical direction on the dust component only. This concentrates the dust around the mid-plane of the disc, and an equilibrium distribution of the dust density is achieved when the vertical settling is counteracted by the turbulent diffusion away from the mid-plane. Comparing with analytical expressions for the equilibrium concentration we deduce the vertical turbulent diffusion coefficient. The vertical diffusion coefficient is found to be lower than the turbulent viscosity and to have an associated vertical diffusion Prandtl number of about 1.5. A similar radial force field also allows us to measure the radial turbulent diffusion coefficient. We find a radial diffusion Prandtl number of about 0.85 and also find that the radial turbulent diffusion coefficient is around 70% higher than the vertical. We also find evidence for trapping of dust grains of intermediate friction time in turbulent eddies.
Johansen Anders
Klahr Hubert
No associations
LandOfFree
Dust diffusion in protoplanetary discs by magnetorotational turbulence does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Dust diffusion in protoplanetary discs by magnetorotational turbulence, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dust diffusion in protoplanetary discs by magnetorotational turbulence will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-286909