Streaming Instability: An aerodynamic instability arising from the relative drift and the mutual drag forces between gas and solids in protoplanetary disks.
Li et al., The Astrophysical Journal, vol. 885, #1, 'Demographics of Planetesimals Formed by the Streaming Instability' (2019, open accesslink)
Description:
As abundances of solids and gas reach parity, the streaming instability promotes dust concentration through self-gravitation. This occurs at specific locations near the disk midplane, such as pressure bumps, the water ice line, and the silicate sublimation line. These self-bound clumps, or pebbles, then rapidly collapse to form size-sorted planetesimals that can ultimately reach multi-km-scale sizes.
Reference: Jacquet et al., Space Science Reviews, 'Evolution of the Solar System: Constraints from Meteorites', 2023 ISSI Workshop (2024, open accesslink)
Additional references of interest:
Estrada and Umurhan, The Astrophysical Journal, vol. 946, #1, 'Formation of the First Planetesimals via the Streaming Instability in Globally Turbulent Protoplanetary Disks?' (2023, open accesslink)
A general discussion of the physics of turbulent particle growth in the early protoplanetary disk, including particle trapping by vortices, turbulent concentration, and the streaming instability.
See an MP4 video that illustrates the streaming instability:
Video credit: Nesvorný et al., Nature Astronomy, vol. 3, Supplementary Information
'Trans-Neptunian Binaries as Evidence for Planetesimal Formation by the Streaming Instability'
(2019, or open access arXivlink)