A Two‐Fluid Analysis of the Kelvin‐Helmholtz Instability in the Dusty Layer of a Protoplanetary Disk: A Possible Path toward Planetesimal Formation through Gravitational Instability

Michikoshi, Shugo; Inutsuka, Shu‐ichiro

doi:10.1086/499799

Cited by 26 publications

(39 citation statements)

References 22 publications

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“…The latter is a wellknown hydrodynamic instability caused by a shear flow velocity at the interface between two fluids (see Chandrasekhar 1961). A great number of papers have been devoted to the study of this instability in many astrophysical environments, such as Earth's aurora (Hallinan & Davis 1970), protoplanetary disks (Michikoshi & Inutsuka 2006), the magnetopause (Guo et al 2010), or planetary magnetospheres (Ogilvie & Fitzenreiter 1989). In solar coronal plasmas this instability has been observed in coronal mass ejections, for instance (Foullon et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Onset of the Kelvin-Helmholtz instability in partially ionized magnetic flux tubes

Martínez‐Gómez

Soler

Terradas

2015

A&A

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Context. Recent observations of solar prominences show the presence of turbulent flows that may be caused by Kelvin-Helmholtz instabilites (KHI). However, the observed flow velocities are below the classical threshold for the onset of KHI in fully ionized plasmas. Aims. We investigate the effect of partial ionization on the onset of KHI in dense and cool cylindrical magnetic flux tubes surrounded by a hotter and lighter environment. Methods. The linearized governing equations of a partially ionized two-fluid plasma were used to describe the behavior of smallamplitude perturbations superimposed on a magnetic tube with longitudinal mass flow. A normal mode analysis was performed to obtain the dispersion relation for linear incompressible waves. We focused on the appearance of unstable solutions and studied the dependence of their growth rates on various physical parameters. We obtained an analytical approximation of the KHI linear growth rate for slow flows and strong ion-neutral coupling. We applied this to solar prominence threads. Results. The presence of a neutral component in a plasma may contribute to the onset of the KHI even for sub-Alfvénic longitudinal shear flows. Collisions between ions and neutrals reduce the growth rates of the unstable perturbations, but cannot completely suppress the instability. Conclusions. Turbulent flows in solar prominences with sub-Alfvénic flow velocities may be interpreted as consequences of KHI in partially ionized plasmas.

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Section: Introductionmentioning

confidence: 99%

Onset of the Kelvin-Helmholtz instability in partially ionized magnetic flux tubes

Martínez‐Gómez

Soler

Terradas

2015

A&A

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“…Far away ( 100 AU) from the sun, when the hot solar wind meets the cold interstellar medium, the boundary layer between them may become Kelvin-Helmholtz unstable (Dasgupta et al 2011). Shear instabilities in the dust layer of the solar nebula may inhibit the formation of planetisimals (Sekiya 1998;Sekiya & Ishitsu 2001;Michikoshi & Inutsuka 2006;Hasegawa & Toru 2014). It is quite plausible that the KH instability is responsible for the narrower line profiles in the ionized spices in molecular clouds (Watson et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Can Hall effect trigger Kelvin–Helmholtz instability in sub-Alfvénic flows?

Pandey

2018

Monthly Notices of the Royal Astronomical Society

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In the Hall magnetohydrodynamics, the onset condition of the Kelvin-Helmholtz instability is solely determined by the Hall effect and is independent of the nature of shear flows. In addition, the physical mechanism behind the super and sub-Alfvénic flows becoming unstable is quite different: the high frequency right circularly polarized whistler becomes unstable in the super-Alfvénic flows whereas low frequency, left circularly polarized ion-cyclotron wave becomes unstable in the presence of sub-Alfvénic shear flows. The growth rate of the Kelvin-Helmholtz instability in the super-Alfvénic case is higher than the corresponding ideal magnetohydrodynamic rate. In the sub-Alfvénic case, the Hall effect opens up a new, hitherto inaccessible (to the magnetohydrodynamics) channel through which the partially or fully ionized fluid can become Kelvin-Helmholtz unstable. The instability growth rate in this case is smaller than the super-Alfvénic case owing to the smaller free shear energy content of the flow.When the Hall term is somewhat smaller than the advection term in the induction equation, the Hall effect is also responsible for the appearance of a new overstable mode whose growth rate is smaller than the purely growing Kelvin-Helmholtz mode. On the other hand, when the Hall diffusion dominates the advection term, the growth rate of the instability depends only on the Alfvén -Mach number and is independent of the Hall diffusion coefficient. Further, the growth rate in this case linearly increase with the Alfvén frequency with smaller slope for sub-Alfvénic flows.

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“…In this way, the KHI can potentially disrupt the growths to higher density in the midplane, or dynamically cause higher densities in some regions. This has been studied analytically as well as numerically in Michikoshi & Inutsuka (2006), Johansen et al (2006), and Barranco (2009).…”

Section: Introductionmentioning

confidence: 99%

Effect of dust on Kelvin-Helmholtz instabilities

Hendrix

Keppens

2014

A&A

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Context. Dust is present in a large variety of astrophysical fluids, ranging from tori around supermassive black holes to molecular clouds, protoplanetary discs, and cometary outflows. In many such fluids, shearing flows are present, which can lead to the formation of Kelvin-Helmholtz instabilities (KHI) and may change the properties and structures of the fluid through processes such as mixing and clumping of dust. Aims. We study the effects of dust on the KHI by performing numerical hydrodynamical dust+gas simulations. We investigate how the presence of dust changes the growth rates of the KHI in 2D and 3D and how the KHI redistributes and clumps dust. We investigate if similarities can be found between the structures in 3D KHI and those seen in observations of molecular clouds. Methods. We perform numerical multifluid hydrodynamical simulations in addition to the gas a number of dust fluids. Each dust fluid represents a portion of the particle size-distribution. We study how dust-to-gas mass density ratios between 0.01 and 1 alter the growth rate in the linear phase of the KHI. We do this for a wide range of perturbation wavelengths, and compare these values to the analytical gas-only growth rates. As the formation of high-density dust structures is of interest in many astrophysical environments, we scale our simulations with physical quantities that are similar to values in molecular clouds. Results. Large differences in dynamics are seen for different grain sizes. We demonstrate that high dust-to-gas ratios significantly reduce the growth rate of the KHI, especially for short wavelengths. We compare the dynamics in 2D and 3D simulations, where the latter demonstrates additional full 3D instabilities during the non-linear phase, leading to increased dust densities. We compare the structures formed by the KHI in 3D simulations with those in molecular clouds and see how the column density distribution of the simulation shares similarities with log-normal distributions with power-law tails sometimes seen in observations of molecular clouds.

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A Two‐Fluid Analysis of the Kelvin‐Helmholtz Instability in the Dusty Layer of a Protoplanetary Disk: A Possible Path toward Planetesimal Formation through Gravitational Instability

Cited by 26 publications

References 22 publications

Onset of the Kelvin-Helmholtz instability in partially ionized magnetic flux tubes

Onset of the Kelvin-Helmholtz instability in partially ionized magnetic flux tubes

Can Hall effect trigger Kelvin–Helmholtz instability in sub-Alfvénic flows?

Effect of dust on Kelvin-Helmholtz instabilities

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