Numerical simulation of MRI: towards a systematic characterization of turbulent transport in accretion disks.

From the early 90s, the magneto rotational instability has found to be the most promising instability to explain turbulent transport in accretion disks. However, some important issues have been overlooked in previous studies and need to be studied to quantify the role of MRI-driven turbulence in disks. We present here a numerical study using a pseudo spectral incompressible 3D code, with explicit viscosity and resistivity. First, we show that close to the marginal stability limit, the turbulent transport is unexpectedly large, and highly time-dependent. Second, we exhibit a substantial dependance of the global transport on the magnetic Prandtl number, which may have an important role in many astrophysical objects such as YSO accretion disks (Pr=10^-8). More generally, these results exhibit the need to control the dissipation process in astrophysical simulations.