- Lectures
- Institute of Astronomy and Astrophysics
- Location
R1203 of the Astronomy-Mathematics Building, National Taiwan University
- Speaker Name
Yuya Fukuhara, Institute of Science Tokyo
- State
Definitive
- Url
Turbulence in protoplanetary disks affects dust evolution and planetesimal formation. The vertical shear instability (VSI) is one of the candidate turbulence-driving mechanisms in the outer part of the disks. Since the VSI requires rapid gas cooling, dust particles in disks can influence and potentially control VSI-driven turbulence. However, VSI-driven turbulence has strong vertical motion, causing vertical diffusion of dust particles. We perform global two-dimensional hydrodynamical simulations of an axisymmetric protoplanetary disk to investigate how the VSI drives turbulence and maintains a balance between dust settling and diffusion. These simulations account for the dynamic interplay between dust distribution, cooling rates, and VSI-driven turbulence. We find that VSI mixing, dust settling, and the local dust cooling reach an equilibrium, forming a thick dust layer with a dimensionless vertical mixing coefficient of approximately $10^{-3}$. The ability of VSI to sustain this equilibrium depends on dust size and dust-to-gas mass ratio. Larger grains or lower mass ratios weaken the turbulence, leading to dust settling. Our results suggest that in VSI-dominated disks, dust grows under turbulence with intensity varying by dust size. Finally, I will talk about the application of the early disk stage and further planet formation.