How Efficient Is the Streaming Instability in Viscous Protoplanetary Disks?

The streaming instability is a popular candidate for planetesimal formation by concentrating dust particles to trigger gravitational collapse. However, its robustness against the physical conditions expected in protoplanetary disks is unclear. In particular, particle stirring by turbulence may imped...

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Bibliographic Details
Published in:The Astrophysical journal 2020-03, Vol.891 (2), p.132
Main Authors: Chen, Kan, Lin, Min-Kai
Format: Article
Language:English
Subjects:
Alpha rays
Astrophysics
Celestial bodies
Compressibility
Diffusion
Diffusion effects
Diffusion rate
Disks
Dust
Dust particles
Exoplanet formation
Extrasolar planets
Gas viscosity
Gravitational collapse
Hydrodynamics
Instability
Particle diffusion
Planet formation
Planetesimals
Protoplanetary disks
Protoplanets
Solar corona
Solar nebula
Space telescopes
Stability
Stokes number
Turbulence
Viscosity
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Summary:The streaming instability is a popular candidate for planetesimal formation by concentrating dust particles to trigger gravitational collapse. However, its robustness against the physical conditions expected in protoplanetary disks is unclear. In particular, particle stirring by turbulence may impede the instability. To quantify this effect, we develop the linear theory of the streaming instability with external turbulence modeled by gas viscosity and particle diffusion. We find the streaming instability is sensitive to turbulence, with growth rates becoming negligible for alpha viscosity parameters , where is the particle Stokes number. We explore the effect of nonlinear drag laws, which may be applicable to porous dust particles, and find growth rates are modestly reduced. We also find that gas compressibility increases growth rates by reducing the effect of diffusion. We then apply the linear theory to global models of viscous protoplanetary disks. For minimum-mass solar nebula disk models, we find the streaming instability only grows within disk lifetimes beyond tens of astronomical units, even for centimeter-sized particles and weak turbulence ( ). Our results suggest it is rather difficult to trigger the streaming instability in nonlaminar protoplanetary disks, especially for small particles.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ab76ca