Turbulence in weakly-ionized proto-planetary disks

TL;DR

This study explores the behavior of magnetorotational instability (MRI) turbulence in weakly-ionized proto-planetary disks through 3D simulations, identifying the conditions under which turbulence is sustained or decays.

Contribution

It provides the first detailed analysis of the transition regime between active and dead zones in proto-planetary disks using global non-ideal MHD simulations.

Findings

MRI turbulence saturates for Rm > 5000 with alpha ~ 0.01

MRI decays below Rm < 5000, with a damped transition regime between 3300 and 5000

MRI cannot be sustained below Rm < 3000, leading to decay and dominance of hydrodynamical motions

Abstract

We investigate the characteristic properties of self-sustained MRI turbulence in low-ionized proto-planetary disks. We study the transition regime between active and dead-zone, performing 3D global non-ideal MHD simulations of stratified disk covering range of magnetic Reynolds number between 2700 < Rm < 6600. We found converged and saturated MRI turbulence for Rm > 5000 with a strength of alpha ~ 0.01. Below Rm < 5000 the MRI starts to decay at the midplane, having Elsasser numbers below one. We find a transition regime between 3300 < Rm < 5000 where the MRI turbulence is still sustained but damped. At around Rm < 3000 the MRI turbulence decays but could reestablished due to the accumulation of toroidal magnetic field or the radial transport of magnetic field from the active region. Below Rm < 3000 the MRI cannot be sustained and is decaying. Here hydro-dynamical motions, like density waves dominate. We observe anti-cyclonic vortices in the transition between dead-zone and active zone.