Disk Winds: Simulations and Constraints from ALMA Surveys

During the process of low-mass star formation, a protostar is inevitably surrounded by a flattened, centrifugally-supported circumstellar disk. For mass accretion to proceed in such disks, angular momentum transport must take place. Canonically, a protoplanetary disk is thought to accrete viscously, wherein the angular momentum is redistributed within the disk. The primary source of viscosity is considered to be magnetorotational instability (MRI) which causes turbulence in the presence of weakly ionized gas and magnetic field. However, several lines of observational evidence now shows that the turbulence in a typical protoplanetary disk is insufficient to drive accretion. Conversely, when all of the non-ideal magnetohydrodynamic effects are included, the simulations also point towards suppression of MRI. Instead, magnetic disk winds are now considered crucial for disk evolution, which evacuate the angular momentum and mass vertically out of the plane of the disk. In this presentation, I will talk about the results of numerical simulations of formation and evolution of protoplanetary disks, which include the concurrent effects of gravitational and viscous torques, along with magnetic disk winds. I will discuss the long-term evolution of protoplanetary disks, wherein the disk forms and evolves through Class 0, I and II stages. I will also discuss the central role of disk winds in deciding the fundamental disk properties and implications derived from comparison with the observed populations of Class II disks from large-scale ALMA surveys.