Oral Presentation

Dust concentration and thresholds for planetesimal formation explored in two-dimensional global models of streaming instability and vertical shear instability

Author(s): Urs Schäfer (University of Copenhagen, Denmark) Anders Johansen (University of Copenhagen, Denmark; Lund University, Sweden)

Presenter: Urs Schäfer (Centre for Star and Planet Formation, Globe Institute, University of Copenhagen)

The streaming instability is arguably the most promising mechanism to induce the formation of planetesimals, a key step in the growth from dust grains to planets. Nonetheless, planetesimal formation via the streaming instability has been found in previous studies to require either a dust-to-gas ratio or a dust size that is enhanced compared to observed values. We employ two-dimensional adaptive mesh refinement simulations of protoplanetary disks on a global scale to investigate dust concentration and the potential for planetesimal formation owing to the streaming instability in concert with another hydrodynamic instability, the vertical shear instability. Our simulations show that the two instabilities in conjunction can cause dust concentration that is sufficient for planetesimal formation for lower dust-to-gas ratios and smaller dust sizes than the streaming instability in isolation, and in particular under conditions that are consistent with observational constraints. This is because dust accumulating in pressure bumps induced by the vertical shear instability seeds the streaming instability, which in turn reinforces both pressure bumps and dust accumulations.