Streaming instability

The streaming instability is an instability of mutually coupled gas and solid particles in a disk. Relative drift and drag can concentrate the particles into dense structures.

A streaming-instability resonance occurs when a gas wave has frequency $\omega =\mathbf{k}\cdot \Delta \mathbf{u}$, matching the wave phase to the particle drift. The resonant forcing then produces algebraic particle-density growth in the test-particle limit.