Dust settling in turbulent protoplanetary disks

Min-Kai Lin^1*

¹ASIAA, Academia Sinica, Taipei, Taiwan

* Presenter:Min-Kai Lin, email:mklin@asiaa.sinica.edu.tw

Planets are formed in disks of gas and dust around young stars called protoplanetary disks. In the standard `core accretion' scenario, the first step towards planet formation is the coagulation of small dust grains into planetesimals. This requires the concentration of dust grains to the point of triggering gravitational instabilities, either directly or indirectly. Thus, dust-concentration mechanisms are of considerable interest to the planet formation community. One mechanism is dust-settling: dust particles sediment to the disk mid-plane owing to the vertical component of stellar gravity. However, this process can be hindered by turbulence in the disk. I present numerical simulations of dust settling in protoplanetary disks subject to hydrodynamic turbulence driven by the `vertical shear instability' (VSI). I demonstrate the VSI can effectively lift small dust particles, which prevents their settling. However, increasing the particle size and/or the total solid abundance can potentially overcome VSI stirring. I propose a self-sustaining cycle that allows dust to continually settle, provided certain initial conditions are met. Implications for planetesimal formation will be briefly discussed.

Keywords: planet formation, astrophysical fluid dynamics, accretion disks, computational astrophysics , theoretical astrophysics