Turbulent Mixing and the Dead Zone in Protostellar Disks

By N. J. Turner, Takayoshi Sano, N. Dziourkevitch. 2006

153 citations recorded by the source corpus.

We investigate the conditions for the presence of a magnetically inactive dead zone in protostellar disks using three-dimensional shearing-box MHD calculations, including vertical stratification, ohmic resistivity, and time-dependent ionization chemistry. Activity driven by the magneto-rotational instability fills the whole thickness of the disk at 5 AU, provided cosmic-ray ionization is present, small grains are absent, and the gas-phase metal abundance is sufficiently high. At 1 AU, the larger column density of 1700 g cm-2 means the midplane is shielded from ionizing particles and remains magneto-rotationally stable, even under the most favorable conditions considered. Nevertheless, the dead zone is effectively eliminated. Turbulence mixes free charges into the interior as they recombine, leading to a slight coupling of the midplane gas to the magnetic fields. Weak, large-scale radial fields diffuse to the midplane, where they are sheared out to produce stronger azimuthal fields. On average, the resulting midplane accretion stresses are just a few times less than in the surface layers.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/7fabd4dc8d2f0c17dacc26279c35cb53fa51ef4d

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Citations in the corpus

Global Simulations of the Inner Regions of Protoplanetary Disks with Comprehensive Disk Microphysics (2017, background): “We note that the rate of cosmic-ray ionization rate bears large uncertainties (e.g., McCall et al. 2003; Cleeves et al. 2013a), though it would not change the fact that the midplane region of the inner disk is ionized extremely weakly, suppressing the MRI (Bai 2011).”
Thanatology in protoplanetary discs - The combined influence of Ohmic, Hall, and ambipolar diffusion on dead zones (2014, background): “S R ] 2 4 Fe b 20 14 2000; Fromang et al. 2002; Ilgner & Nelson 2006a,b) and threedimensional numerical simulations (Fleming et al. 2000; Fleming & Stone 2003; Turner et al. 2007; Ilgner & Nelson 2008).”
Dead Zone Accretion Flows in Protostellar Disks (2008, background): “In other respects the calculations are identical to our recent work (Turner et al. 2007).”
EFFECT OF AMBIPOLAR DIFFUSION ON THE NONLINEAR EVOLUTION OF MAGNETOROTATIONAL INSTABILITY IN WEAKLY IONIZED DISKS (2011, background): “…in PPDs, where the surface layer of the disk is sufficiently ionized to couple to the magnetic field and drive the MRI turbulence, while the midplane region is too poorly ionized and “dead” (Fleming & Stone 2003; Turner et al. 2007; Turner & Sano 2008; Ilgner & Nelson 2008; Oishi & Mac Low 2009).”
Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations (2014, background): “Inside the gap, the Elsasser number peaks at 0.1, which enables MRI activity (Turner et al. 2007; Okuzumi & Hirose 2011; Flock et al. 2012b).”
WIND-DRIVEN ACCRETION IN PROTOPLANETARY DISKS. I. SUPPRESSION OF THE MAGNETOROTATIONAL INSTABILITY AND LAUNCHING OF THE MAGNETOCENTRIFUGAL WIND (2013, methodology): “In regions near the disk midplane where Ohmic resistivity dominates, the Ohmic Elsasser number is below one within about z = ±2H , too small for the MRI to operate (Turner et al. 2007).”
The great dichotomy of the Solar System: Small terrestrial embryos and massive giant planet cores (2015, background): “In fact, some turbulence can be sustained in the dead zone due to a number of effects, e.g. diffusion of the magnetic accretion stress (Turner et al., 2007), baroclynic instability (Klahr and Bodenheimer, 2003), vertical shear instability (Nelson et al., 2013).”
Toward Planetesimals: Dense Chondrule Clumps in the Protoplanetary Nebula (2008, background): “The widely accepted magnetorotational instability (MRI) (Stone et al 2000) may or may not be precluded at the high gas densities of the inner solar system (Turner et al 2007).”
Grain Retention and Formation of Planetesimals near the Snow Line in MRI-driven Turbulent Protoplanetary Disks (2007, methodology): “As the active region switches from covering the entire thickness of the disk to being virtually non-existent in the presence of a significant population of small particles (Turner et al. 2007), we can utilize our simple α description from eq(3) where α1 = αMRI and α2 = α0.”
Global simulations of protoplanetary disks with net magnetic flux: I. Non-ideal MHD case (2016, background): “Large-scale magnetic fields are observed in the vicinity of protoplanetary disks, hosted by the parent molecular cloud and 1 Reduced chemical models can nonetheless be computationally affordable, see for example Turner et al. (2007), Ilgner & Nelson (2008).”