Turbulence in weakly ionized protoplanetary disks

Abstract

We investigate the characteristic properties of self-sustained magneto-rotational instability (MRI) turbulence in low-ionized protoplanetary disks. We study the transition regime between active and dead zones, performing three-dimensional global non-ideal MHD simulations of stratified disks covering a range of magnetic Reynolds numbers between 2700 ≲ Rm≲ 6600. We found converged and saturated MRI turbulence for Rm5000 with a strength of αSS∼ 0.01. Below Rm≲ 5000, the MRI starts to decay at the midplane at first because the Elsasser number drops below 1. We find a transition regime between 3300 Rm 5000 where the MRI turbulence is still sustained but damped. At around Rm3000, the MRI turbulence decays but could be reestablished due to the accumulation of the toroidal magnetic field or the radial transport of the magnetic field from the active region. Below Rm< 3000, the MRI cannot be sustained and is decaying. Here, hydrodynamical motions, like density waves, dominate. We observe anti-cyclonic vortices in the transition between the dead zone and the active zone. © 2012. The American Astronomical Society. All rights reserved..