Wind-Driven Global Evolution of Protoplanetary Disks

Abstract

It has been realized in the recent years that magnetized disk winds likely play a decisive role in the global evolution of protoplanetary disks (PPDs). Motivated by recent local simulations , we first describe a global magnetized disk wind model, from which wind-driven accretion rate and wind mass loss rate can be reliably estimated. Both rates are shown to strongly depend on the amount of magnetic flux threading the disk. Wind kinematics is also affected by thermodynamics in the wind zone (particularly far UV heating/ionization), and the mass loss process can be better termed as “magneto-photoevaporation.” We then construct a framework of PPD global evolution that incorporates wind-driven and viscously driven accretion as well as wind mass loss. For typical PPD accretion rates, the required field strength would lead to wind mass loss rate at least comparable to disk accretion rate, and mass loss is most significant in the outer disk (beyond ∼ 10 AU). Finally, we discuss the transport of magnetic flux in PPDs, which largely governs the long-term evolution of PPDs.