Resonant drag instabilities for polydisperse dust. II. The streaming and settling instabilities

Abstract

Dust grains embedded in gas flow give rise to a class of hydrodynamic instabilities, called resonant drag instabilities. These instabilities have predominantly been studied for single grain sizes, in which case they are found to grow fast. Nonlinear simulations indicate that strong dust overdensities can form, aiding the formation of planetesimals. In reality, however, there is going to be a distribution of dust sizes, which potentially has important consequences. We study two different resonant drag instabilities, the streaming instability and the settling instability, taking into account a continuous spectrum of grain sizes, to determine whether these instabilities survive in the polydisperse regime and how the resulting growth rates compare to the monodisperse case. We solve the linear equations for a polydisperse fluid in an unstratified shearing box to recover the streaming instability and, for approximate stratification, the settling instability, in all cases focusing on small dust-to-gas ratios. Size distributions of realistic width turn the singular perturbation of the monodisperse limit into a regular perturbation due to the fact that the backreaction on the gas involves an integration over the resonance. The contribution of the resonance to the integral can be negative, as in the case of the streaming instability, which as a result does not survive in the polydisperse regime, or positive, which is the case in the settling instability. The latter therefore has a polydisperse counterpart, with growth rates that can be comparable to the monodisperse case. Wide size distributions in almost all cases remove the resonant nature of drag instabilities. This can lead to reduced growth, as is the case in large parts of parameter space for the settling instability, or complete stabilisation, as is the case for the streaming instability.

17 pages, 12 figures, accepted for publication in A&A

References in corpus (15)

• Array Programming with NumPy
• Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample
• On disc protoplanet interactions in a non-barotropic disc with thermal diffusion
• Streaming Instability for Particle-Size Distributions
• A thermodynamic view of dusty protoplanetary disks
• Testing the Jeans, Toomre and Bonnor-Ebert concepts for planetesimal formation: 3D streaming instability simulations of diffusion regulated formation of planetesimals
• Local models of astrophysical discs
• Streaming Instability with Multiple Dust Species: II. Turbulence and Dust-Gas Dynamics at Nonlinear Saturation
• Polydisperse Streaming Instability III. Dust evolution encourages fast instability
• Stratified and vertically-shearing streaming instabilities in protoplanetary disks
• Streaming instability of multiple particle species II -- Numerical convergence with increasing particle number
• Polydisperse Streaming Instability II. Methods for solving the linear stability problem
• Instabilities in dusty non-isothermal proto-planetary discs
• Planetesimal formation via the streaming instability with multiple grain sizes
• Resonant Drag Instabilities for Polydisperse Dust, I. The Acoustic Resonant Drag Instability

Cited by in corpus (2)

• Nonlinear Evolution of the Unstratified Polydisperse Dust Settling Instability
• A multi-fluid approach for polydisperse pebble accretion: From particles to fluids, establishing the multifluid framework