Temperature Structure in the Inner Regions of Protoplanetary Disks: Inefficient Accretion Heating Controlled by Nonideal Magnetohydrodynamics

Mori, Shoji; Bai, Xue-Ning; Okuzumi, Satoshi

doi:10.3847/1538-4357/ab0022

Cited by 70 publications

(77 citation statements)

References 77 publications

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“…As the luminosity of the Sun decreases with the contraction of the protostar, the water ice line moves interior of 1 AU after around 1.5 Ma to 2 Ma in both models. Because the limiting case where viscous heating is applied everywhere is not physically realistic, as demonstrated in magnetohydrodynamical simulations ( 30 ), we adopt the dead zone model when integrating the growth tracks of planets. Overall, we infer from the dead zone model that the first planetesimals in the inner Solar Systems likely formed in a region devoid of magnetically driven turbulence between 1.2 and 2.0 AU.…”

Section: Resultsmentioning

confidence: 99%

A pebble accretion model for the formation of the terrestrial planets in the Solar System

et al. 2021

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Pebbles of millimeter sizes are abundant in protoplanetary discs around young stars. Chondrules inside primitive meteorites—formed by melting of dust aggregate pebbles or in impacts between planetesimals—have similar sizes. The role of pebble accretion for terrestrial planet formation is nevertheless unclear. Here, we present a model where inward-drifting pebbles feed the growth of terrestrial planets. The masses and orbits of Venus, Earth, Theia (which later collided with Earth to form the Moon), and Mars are all consistent with pebble accretion onto protoplanets that formed around Mars’ orbit and migrated to their final positions while growing. The isotopic compositions of Earth and Mars are matched qualitatively by accretion of two generations of pebbles, carrying distinct isotopic signatures. Last, we show that the water and carbon budget of Earth can be delivered by pebbles from the early generation before the gas envelope became hot enough to vaporize volatiles.

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Section: Resultsmentioning

confidence: 99%

A pebble accretion model for the formation of the terrestrial planets in the Solar System

et al. 2021

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“…Unrealistic single grain opacities (typically of micrometer size particles) result in discs that are too hot. This implies that potentially other heating sources are needed to keep the iceline at large orbital distances, especially if viscous heating is low (Mori et al 2019).…”

Section: Au (26)mentioning

confidence: 99%

Influence of grain growth on the thermal structure of protoplanetary discs

Savvidou

Bitsch

Lambrechts

2020

A&A

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The thermal structure of a protoplanetary disc is regulated by the opacity that dust grains provide. However, previous works have often considered simplified prescriptions for the dust opacity in hydrodynamical disc simulations, for example, by considering only a single particle size. In the present work, we perform 2D hydrodynamical simulations of protoplanetary discs where the opacity is self-consistently calculated for the dust population, taking into account the particle size, composition, and abundance. We first compared simulations utilizing single grain sizes to two different multi-grain size distributions at different levels of turbulence strengths, parameterized through the α-viscosity, and different gas surface densities. Assuming a single dust size leads to inaccurate calculations of the thermal structure of discs, because the grain size dominating the opacity increases with orbital radius. Overall the two grain size distributions, one limited by fragmentation only and the other determined from a more complete fragmentation-coagulation equilibrium, give comparable results for the thermal structure. We find that both grain size distributions give less steep opacity gradients that result in less steep aspect ratio gradients, in comparison to discs with only micrometer-sized dust. Moreover, in the discs with a grain size distribution, the innermost (<5 AU) outward migration region is removed and planets embedded in such discs experience lower migration rates. We also investigated the dependency of the water iceline position on the alpha-viscosity (α), the initial gas surface density (Σg,0) at 1 AU and the dust-to-gas ratio (fDG) and find rice ∝ α0.61Σg,00.8fDG0.37 independently of the distribution used in the disc. The inclusion of the feedback loop between grain growth, opacities, and disc thermodynamics allows for more self-consistent simulations of accretion discs and planet formation.

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“…However, it should be noted that the validity of viscous disk models has been challenged in the recent years (see, e.g., Turner et al 2014;Gressel et al 2015;Bai 2017) due to the fact that non-ideal MHD effects tend to suppress the source of turbulent viscosity in the disk, and their evolution would then rather be driven by thermo-magnetic winds. This possibly results in inefficient viscous heating of the disks (Mori et al 2019). The non-ideal MHD effects are expected to dominate even more in the case of CPDs (Fujii et al 2014(Fujii et al , 2017, so that CPDs could be denser than advocated by Canup & Ward (2002) while remaining cold.…”

Section: Motivationmentioning

confidence: 99%

Formation of moon systems around giant planets

Ronnet

Johansen

2020

A&A

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The four major satellites of Jupiter, known as the Galilean moons, and Saturn’s most massive satellite, Titan, are believed to have formed in a predominantly gaseous circum-planetary disk during the last stages of formation of their parent planet. Pebbles from the protoplanetary disk are blocked from flowing into the circumplanetary disk by the positive pressure gradient at the outer edge of the planetary gap, so the gas drag assisted capture of planetesimals should be the main contributor to the delivery of solids onto circum-planetary disks. However, a consistent framework for the subsequent accretion of the moons remains to be built. Here, we use numerical integrations to show that most planetesimals that are captured within a circum-planetary disk are strongly ablated due to the frictional heating they experience, thus supplying the disk with small dust grains, whereas only a small fraction “survives” their capture. We then constructed a simple model of a circum-planetary disk supplied by ablation, where the flux of solids through the disk is at equilibrium with the ablation supply rate, and we investigate the formation of moons in such disks. We show that the growth of satellites is mainly driven by accretion of the pebbles that coagulate from the ablated material. The pebble-accreting protosatellites rapidly migrate inward and pile up in resonant chains at the inner edge of the circum-planetary disk. We propose that dynamical instabilities in these resonant chains are at the origin of the different architectures of Jupiter’s and Saturn’s moon systems. The assembly of moon systems through pebble accretion can therefore be seen as a down-scaled manifestation of the same process that forms systems of super-Earths and terrestrial-mass planets around solar-type stars and M-dwarfs.

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Temperature Structure in the Inner Regions of Protoplanetary Disks: Inefficient Accretion Heating Controlled by Nonideal Magnetohydrodynamics

Cited by 70 publications

References 77 publications

A pebble accretion model for the formation of the terrestrial planets in the Solar System

A pebble accretion model for the formation of the terrestrial planets in the Solar System

Influence of grain growth on the thermal structure of protoplanetary discs

Formation of moon systems around giant planets

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