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)
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)