Global model of magnetic wind-driven accretion in protoplanetary disks

Due to the conservation of angular momentum contained in the parent molecular cloud, a protostar is inevitably surrounded by a flattened, centrifugally-supported circumstellar disk. For accretion to proceed, angular momentum transport must take place in the disk. Canonically, the magnetorotational instability (MRI) was considered to be the primary source of turbulence which could generate viscosity for accretion. However, several lines of reasoning now show that the observed turbulence in a typical protoplanetary disk is insufficient to drive the disk accretion. Conversely, when all of the non-ideal magnetohydrodynamic effects are included, the simulations also point towards suppression of the MRI. In this talk, I will present a global model of magnetic wind-driven accretion, based on numerical magnetohydrodynamics simulations of protoplanetary disks. We study long-term evolution of the disk and show that magnetocentrifugal winds are capable of transporting the angular momentum vertically, which results in sufficiently large accretion rates. I will also discuss the impact of wind-driven accretion on the inner disk structure and its implications for episodic accretion.