Dispersal of protoplanetary discs by the combination of magnetically driven and photoevaporative winds

Abstract

ABSTRACT We investigate the roles of magnetically driven disc wind (MDW) and thermally driven photoevaporative wind (PEW) in the long-time evolution of protoplanetary discs. We start simulations from the early phase in which the disc mass is $0.118\, \rm M_{\odot }$ around a $1\, \rm M_{\odot }$ star and track the evolution until the disc is completely dispersed. We incorporate the mass-loss by PEW and the mass-loss and magnetic braking (wind torque) by MDW, in addition to the viscous accretion, viscous heating, and stellar irradiation. We find that MDW and PEW, respectively, have different roles: magnetically driven wind ejects materials from an inner disc in the early phase, whereas photoevaporation has a dominant role in the late phase in the outer (≳1 au) disc. The disc lifetime, which depends on the combination of MDW, PEW, and viscous accretion, shows a large variation of ∼1–20 Myr; the gas is dispersed mainly by the MDW and the PEW in the cases with a low viscosity and the lifetime is sensitive to the mass-loss rate and torque of the MDW, whereas the lifetime is insensitive to these parameters when the viscosity is high. Even in discs with very weak turbulence, the cooperation of MDW and PEW enables the disc dispersal within a few Myr.