Oral Presentation

Runaway Planetesimal Formation in Turbulent Dust Rings Driven by a Dust Growth-Concentration Feedback Loop

Author(s): Ziyan Xu (University of Copenhagen)

Presenter: Ziyan Xu (University of Copenhagen)

High resolution ALMA observations reveal that dust in protoplanetary disks commonly concentrates into narrow rings, which are widely interpreted as dust traps and promising sites of planetesimal formation via streaming instability. However, how dust evolution within these rings interacts with dust diffusion and feedback processes to regulate the onset of planetesimal formation remains understudied.
We investigate this problem by combining local MHD simulations of streaming instability and global DustPy model of planetesimal formation in dust rings with dust evolution. The simulations show that dust clumping in rings increases the local dust loading, suppressing turbulence and dust diffusion. When incorporated into DustPy, this process produces a positive loop between dust growth, concentration, and diffusion suppression, that can trigger runaway planetesimal formation in rings. In rings undergoing active planetesimal formation, the midplane dust-to-gas ratio self regulates near the streaming instability clumping threshold, consistent with the marginally clumping behavior inferred for many ALMA rings.