Turbulence in outer protoplanetary discs: MRI or VSI?

ABSTRACT The outer protoplanetary discs (PPDs) can be subject to the magnetorotational instability (MRI) and vertical shear (VSI). While both processes drive turbulence in disc, existing numerical simulations have studied them separately. In this paper, we conduct global 3D non-ideal magnetohydrodynamic (MHD) for PPDs, with ambipolar diffusion instantaneous cooling, hence conductive instabilities. Given range of Elsässer numbers (Am) explored, it is found that VSI dominates over MRI when strong (Am = 0.1); co-exist Am 1; overwhelmed by weak 10). Angular momentum transport process primarily driven MHD winds, while viscous accretion due and/or makes a moderate contribution most cases. Spontaneous magnetic flux concentration formation annular substructures remain robust diffusion-dominated ? 1) presence VSI. Ambipolar major contributor phenomenon rather than advection.