On linear dust-gas streaming instabilities in protoplanetary discs

TL;DR

This paper analyzes a linear streaming instability in dusty protoplanetary disks using simplified equations, highlighting the roles of rotation, dust pileups, and drag feedback in the instability's physical origin.

Contribution

It provides a clearer understanding of the physical mechanisms behind dust-gas streaming instabilities, emphasizing the importance of rotational dynamics and pressure maxima.

Findings

Rotation is essential for the instability.

Dust pileups in pressure maxima trigger the instability.

Drag feedback strengthens the pressure maxima.

Abstract

We revisit, via a very simplified set of equations, a linear streaming instability (technically an overstability), which is present in, and potentially important for, dusty protoplanetary disks (Youdin & Goodman 2005). The goal is a better understanding of the physical origin of such instabilities, which are notoriously subtle. Rotational dynamics seem to be essential to this type of instability, which cannot be captured by one-dimensional Cartesian models. Dust `pileups' in moving pressure maxima are an important triggering mechanism of the instability, and drag feedback of dust upon the gas allows these maxima to be strengthened. Coriolis forces and the background drift counteract the effects of the pressure force.