Astrophysics, abstract
astro-ph/0603765

From: Anders Johansen [view email]

Date: Tue, 28 Mar 2006 14:09:54 GMT (14kb)

Turbulent diffusion in protoplanetary discs: The effect of an imposed magnetic field

Authors: Anders Johansen, Hubert Klahr, Antony J. Mee

Comments: 5 pages, 2 figures, submitted to MNRAS

We study the effect of an imposed vertical magnetic field on the turbulent diffusion properties of magnetorotational turbulence in protoplanetary discs. It is well-known that the effective viscosity generated by the turbulence depends strongly on the magnitude of such an external field. In this letter we show that the turbulent diffusion of the flow also changes. The diffusion coefficient does not rise with increasing vertical field as fast as the viscosity does. The vertical Schmidt number, i.e. the ratio between viscosity and vertical diffusion, can be close to 20 for high field magnitudes, whereas the radial Schmidt number is increased from below unity to around 3. We derive power laws for the dependence of both components of the Schmidt number on the field magnitude. Our results may have consequences for the interpretation of observations of the dust distribution and the chemical evolution of protoplanetary discs.

http://arxiv.org/abs/astro-ph/0603765