Dust Evolution And Concentration In Disk Wind-Driven Protoplanetary Disks

Abstract

Both observations and simulations over the last decade have shown that turbulence is less influential than previously thought in governing the dynamics of protoplanetary disks. Magnetized disk winds have instead emerged as the most important mechanism in pro- toplanetary disk evolution and must therefore be considered at every step of the planet formation process. The very first steps of planetary system formation, the growth of dust from micron-sizes to km-size planetesimals, are still a subject of debate. The tremen- dous gains in mass from one regime into the next implies that dust growth in disks must be both quick and efficient, requiring both effective growth by collisional interactions and high concentrations that can trigger rapid planetesimal formation via streaming instability. In this work, I study dust growth within a wind-driven protoplanetary disk model whose properties are informed by current observational constraints. I study the parameter space of turbulence strengths, wind-driven accretion strengths, wind-driven outflow strengths and accretion rates in a search for disks conducive to planetesimal formation. I find that even though wind-driven disks are more conducive to both dust growth and concentration compared to turbulence-driven disks, the streaming instability threshold is only crossed for the least turbulent disks with the most powerful outflow. While planetesimal formation in smooth, wind-driven disks is therefore possible in rare cases, dust concentrations into pressure bumps appear to be vital in the formation of planetary systems.