The Initial Conditions for Planet Formation: Turbulence Driven by Hydrodynamical Instabilities in Disks around Young Stars

Lyra, Wladimir; Umurhan, O. M.

doi:10.1088/1538-3873/aaf5ff

Cited by 94 publications

(64 citation statements)

References 168 publications

(319 reference statements)

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“…Variations of the viscosity parameter α in the 10 −4 -10 −2 range, which is commonly adopted for PSN models, show that the results are qualitatively close to those presented here and that the conclusions remain unchanged. The lowest value α = 10 −4 corresponds to the assumption of an MRI dead zone in our simulation box [45][46][47]. Our results are quite different from those derived by Ali-Dib et al [15] who found very high abundances of solid CO in the vicinity of its iceline.…”

Section: Resultscontrasting

confidence: 84%

The role of ice lines in the formation of Uranus and Neptune

Mousis

Aguichine

Helled

et al. 2020

Phil. Trans. R. Soc. A.

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We aim at investigating whether the chemical composition of the outer region of the protosolar nebula can be consistent with current estimates of the elemental abundances in the ice giants. To do so, we use a self-consistent evolutionary disc and transport model to investigate the time and radial distributions of H 2 O, CO, CO 2 , CH 3 OH, CH 4 , N 2 and H 2 S, i.e. the main O-, C-, N and S-bearing volatiles in the outer disc. We show that it is impossible to accrete a mixture composed of gas and solids from the disc with a C/H ratio presenting enrichments comparable to the measurements (approx. 70 times protosolar). We also find that the C/N and C/S ratios measured in Uranus and Neptune are compatible with those acquired by building blocks agglomerated from solids condensed in the 10–20 AU region of the protosolar nebula. By contrast, the presence of protosolar C/N and C/S ratios in Uranus and Neptune would imply that their building blocks agglomerated from particles condensed at larger heliocentric distances. Our study outlines the importance of measuring the elemental abundances in the ice giant atmospheres, as they can be used to trace the planetary formation location, the origin of their building blocks and/or the chemical and physical conditions of the protosolar nebula. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.

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Section: Resultscontrasting

confidence: 84%

The role of ice lines in the formation of Uranus and Neptune

Mousis

Aguichine

Helled

et al. 2020

Phil. Trans. R. Soc. A.

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“…In Fig. 13, we compare the critical timescale of the VSI with the thermal relaxation timescale as described in Lin & Youdin (2015) and adopted by Malygin et al (2017) and Lyra & Umurhan (2019). For our model we expect the VSI to be quenched inwards of 20 au.…”

Section: The Inner Edge Of the Vsi Active Zonementioning

confidence: 96%

“…The dynamical states of protostellar disks during the first million years after their formation are crucial for understanding planet formation processes. As the coupling of the magnetic field to the gas in these dense and cold disks is believed to be weak (Turner et al 2014;Armitage 2019), it seems likely that various hydrodynamical instabilities play important roles, such as the Goldreich−Schubert−Fricke (GSF) instability (Goldreich & Schubert 1967;Fricke 1968), the convective instability (Cameron & Pine 1973), the Papaloizou−Pringle instability (Papaloizou & Pringle 1984), the baroclinic instability (Klahr & Bodenheimer 2003;Lesur ical timescale (Urpin & Brandenburg 1998;Nelson et al 2013;Lin & Youdin 2015;Richard et al 2016;Malygin et al 2017;Latter & Papaloizou 2018;Pfeil & Klahr 2019;Lyra & Umurhan 2019). Recent hydrodynamical simulations have found that the VSI develops in the non-linear regime to produce vortices (Richard et al 2016;Manger & Klahr 2018) due to the Rossby-Wave-Instability (Li et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Gas and Dust Dynamics in Starlight-heated Protoplanetary Disks

Flock

Turner

Nelson

et al. 2020

ApJ

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111

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Theoretical models of the ionization state in protoplanetary disks suggest the existence of large areas with low ionization and weak coupling between the gas and magnetic fields. In this regime hydrodynamical instabilities may become important. In this work we investigate the gas and dust structure and dynamics for a typical T Tauri system under the influence of the vertical shear instability (VSI). We use global 3D radiation hydrodynamics simulations covering all 360 • of azimuth with embedded particles of 0.1 and 1mm size, evolved for 400 orbits. Stellar irradiation heating is included with opacities for 0.1-to 10-µm-sized dust. Saturated VSI turbulence produces a stress-to-pressure ratio of α 10 −4. The value of α is lowest within 30 au of the star, where thermal relaxation is slower relative to the orbital period and approaches the rate below which VSI is cut off. The rise in α from 20 to 30 au causes a dip in the surface density near 35 au, leading to Rossby wave instability and the generation of a stationary, long-lived vortex spanning about 4 au in radius and 40 au in azimuth. Our results confirm previous findings that mm size grains are strongly vertically mixed by the VSI. The scale height aspect ratio for 1mm grains is determined to be 0.037, much higher than the value H/r = 0.007 obtained from millimeter-wave observations of the HL Tau system. The measured aspect ratio is better fit by non-ideal MHD models. In our VSI turbulence model, the mm grains drift radially inwards and many are trapped and concentrated inside the vortex. The turbulence induces a velocity dispersion of ∼ 12 m/s for the mm grains, indicating that grain-grain collisions could lead to fragmentation.

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“…In Flock et al (2017) we found a stress-to-pressure ratio of up to 0.1 for the net vertical magnetic flux case. For temperatures below the ionization threshold we chose stress-to-pressure ratios α DZ between 10 −3 and 5 × 10 −4 , to mimic the accretion activity either by hydrodynamical instabilities (Lyra & Umurhan 2019) or a magnetically driven wind (Béthune et al 2017). We note again that the increase in the stress-to-pressure ratio at the ionization transition has a direct impact on the surface density profile.…”

Section: Model Parametersmentioning

confidence: 99%

Planet formation and migration near the silicate sublimation front in protoplanetary disks

Flock

Turner

Mulders

et al. 2019

A&A

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Context. The increasing number of newly detected exoplanets at short orbital periods raises questions about their formation and migration histories. Planet formation and migration depend heavily on the structure and dynamics of protoplanetary disks. A particular puzzle that requires explanation arises from one of the key results of the Kepler mission, namely the increase in the planetary occurrence rate with orbital period up to 10 days for F, G, K and M stars. Aims. We investigate the conditions for planet formation and migration near the dust sublimation front in protostellar disks around young Sun-like stars. We are especially interested in determining the positions where the drift of pebbles would be stopped, and where the migration of Earth-like planets and super-Earths would be halted. Methods. For this analysis we use iterative 2D radiation hydrostatic disk models which include irradiation by the star, and dust sublimation and deposition depending on the local temperature and vapor pressure. Results. Our results show the temperature and density structure of a gas and dust disk around a young Sun-like star. We perform a parameter study by varying the magnetized turbulence onset temperature, the accretion stress, the dust mass fraction, and the mass accretion rate. Our models feature a gas-only inner disk, a silicate sublimation front and dust rim starting at around 0.08 au, an ionization transition zone with a corresponding density jump, and a pressure maximum which acts as a pebble trap at around 0.12 au. Migration torque maps show Earth-and super-Earth-mass planets halt in our model disks at orbital periods ranging from 10 to 22 days. Conclusions. Such periods are in good agreement with both the inferred location of the innermost planets in multiplanetary systems, and the break in planet occurrence rates from the Kepler sample at 10 days. In particular, models with small grains depleted produce a trap located at a 10-day orbital period, while models with a higher abundance of small grains present a trap at around a 17-day orbital period. The snow line lies at 1.6 au, near where the occurrence rate of the giant planets peaks. We conclude that the dust sublimation zone is crucial for forming close-in planets, especially when considering tightly packed super-Earth systems.

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The Initial Conditions for Planet Formation: Turbulence Driven by Hydrodynamical Instabilities in Disks around Young Stars

Cited by 94 publications

References 168 publications

The role of ice lines in the formation of Uranus and Neptune

The role of ice lines in the formation of Uranus and Neptune

Gas and Dust Dynamics in Starlight-heated Protoplanetary Disks

Planet formation and migration near the silicate sublimation front in protoplanetary disks

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