Turbulent Saturation of the Acoustic Resonant Drag Instability*

The acoustic resonant drag instability (RDI) is a recently proposed instability of relevance to a range of dusty astrophysical environments. The instability results from a resonant interaction between dust streaming through gas and acoustic waves in the gas, producing amplification of sound waves and large fluctuations of dust density.[1] The nonlinear evolution of this instability has been shown in simulations to produce clumping of the dust into filaments, the generation of turbulence, and, under some circumstances, the formation of dust jets.[2] Understanding these behaviors is of relevance to modelling dusty winds such as those around active galactic nuclei, in planetary nebulae, and in molecular clouds.[3] We present simulations of the acoustic RDI under varied Mach number, dust/gas mass ratio, and wavelength. These are compared against both novel and previously proposed analytic estimates of saturation amplitude across different length scales, and the phenomenology of the turbulence produced under different regimes is considered.

[1] P. F. Hopkins and J. Squire, The Resonant Drag Instability (RDI): Acoustic Modes, MNRAS 480, 2813 (2018)

[2] E. R. Moseley, J. Squire, and P. F. Hopkins, Non-Linear Evolution of Instabilities between Dust and Sound Waves, MNRAS 489, 325 (2019)

[3] B. Y. Israeli, A. Bhattacharjee, and H. Qin, Resonant instabilities mediated by drag and electrostatic interactions in laboratory and astrophysical dusty plasmas, arXiv:2303.13640 (2023) (to appear in Phys. Plasmas)