Dead Zone Accretion Flows in Protostellar Disks

By N. J. Turner, Takayoshi Sano. 2008

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Planets form inside protostellar disks in a dead zone where the electrical resistivity of the gas is too high for magnetic forces to drive turbulence. We show that much of the dead zone nevertheless is active and flows toward the star while smooth, large-scale magnetic fields transfer the orbital angular momentum radially outward. Stellar X-ray and radionuclide ionization sustain a weak coupling of the dead zone gas to the magnetic fields, despite the rapid recombination of free charges on dust grains. Net radial magnetic fields are generated in the magnetorotational turbulence in the electrically conducting top and bottom surface layers of the disk, and reach the midplane by ohmic diffusion. A toroidal component to the fields is produced near the midplane by the orbital shear. The process is similar to the magnetization of the solar tachocline. The result is a laminar, magnetically driven accretion flow in the region where the planets form.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5d6e570b59d17718c202c7dbb9f9ff2b77e62c1a

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Citations in the corpus

Towards initial mass functions for asteroids and Kuiper Belt Objects (2010, background): “The most generally accepted (although perhaps not the only) way to drive nebula turbulence is the magnetorotational instability (MRI), in which the turbulent intensity is considerably higher in the dilute gas of the outer (and upper) nebula than in the terrestrial planet region (Turner and Sano, 200”
Planet-Disk Interaction and Orbital Evolution (2012, background): “3.2.1 Effect of a dead zone There have been numerous numerical studies of the dynamics of protoplanetary disks with dead zones (Fleming & Stone, 2003; Ilgner & Nelson, 2008; Turner & Sano, 2008; Oishi & Mac Low, 2009; Gressel, Nelson & Turner, 2011; Flaig et al., 2012).”
GLOBAL SIMULATIONS OF PROTOPLANETARY DISKS WITH OHMIC RESISTIVITY AND AMBIPOLAR DIFFUSION (2015, background): “These field belts can be understood as “undead zones”, that is, a region that does not sustain MRI, but where diffusion can be balanced by the winding-up of preexisting radial field via differential rotation (Turner & Sano 2008).”
IMPLEMENTATION OF THE SHEARING BOX APPROXIMATION IN ATHENA (2010, background): “…the MRI (Fromang et al. 2007; Lesur & Longaretti 2007; Simon & Hawley 2009), the saturation of the MRI in radiation pressure dominated disks (Hirose et al. 2008), and the effects of non-ideal MHD and dust on the properties of the MRI in protostellar disks (Turner & Sano 2008; Ilgner & Nelson 2008).”
NONSTEADY ACCRETION IN PROTOSTARS (2008, background): “Simulations have indicated that active layers can have an effect on non-magnetically active regions below, producing a Reynolds stress promoting accretion in the lower regions (Fleming & Stone 2003; Turner & Sano 2008; Ilgner & Nelson 2008).”
TRANSITIONAL DISKS AS SIGNPOSTS OF YOUNG, MULTIPLANET SYSTEMS (2011, methodology): “The MRI scenario proposed by Chiang & Murray-Clay (2007) also cannot clear the interior disk material.”
ELECTRIC CHARGING OF DUST AGGREGATES AND ITS EFFECT ON DUST COAGULATION IN PROTOPLANETARY DISKS (2009, unknown): “A useful fitting formula is given by Turner & Sano (2008), ζXR(r, z) ≈ ζXR,0 ( r 1 AU )−2( LXR 2 × 1030 erg s−1 ) × { exp ( −χ + g (r, z) χXR ) + exp ( −χ − g (r, z) χXR )} , (49) where LXR is the X-ray luminosity, and ζXR,0 = 2.6 × 10−15s−1 and χXR = 8.0 g cm−2 are the fitting parameters.”
WIND-DRIVEN ACCRETION IN PROTOPLANETARY DISKS. I. SUPPRESSION OF THE MAGNETOROTATIONAL INSTABILITY AND LAUNCHING OF THE MAGNETOCENTRIFUGAL WIND (2013, background): “Note that although this is phenomenologically similar to the “undead” zone proposed by Turner & Sano (2008), it is conceptually very different.”
Thanatology in protoplanetary discs - The combined influence of Ohmic, Hall, and ambipolar diffusion on dead zones (2014, background): “This effect is distinct from the process found by Turner & Sano (2008), in which the magnetic field Ohmically diffuses from the upper active layers down into the midplane, where it exerts a large-scale stress.”
Global Simulations of the Inner Regions of Protoplanetary Disks with Comprehensive Disk Microphysics (2017, methodology): “Taking only Ohmic resistivity into account, the picture of layered accretion has been established (Gammie 1996; Fleming & Stone 2003; Turner & Sano 2008; Oishi & Mac Low 2009), where the MRI is suppressed by resistivity in the midplane region of the inner disk (i.e., the densest region where…”
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).”
Dynamics of Protoplanetary Disks (2010, background): “An analytic form for the ionization rate ζ has been given by Turner & Sano (2008), who find that the results of Igea & Glassgold (1999) for a star emitting 5 keV thermal X-rays at LX = 2× 1030 erg s−1 can be fit as, ζ(∆Σ) = 2.6× 10−15 ( r 1 AU )−2 exp [ −∆Σ/8.0 g cm−2 ] s−1, (31) where ∆Σ is the…”
Differentiated Planetesimals and the Parent Bodies of Chondrites (2013, background): “Magnetohydrodynamical simulations predict nebular fields of order 0.01–0.1 mT in the midplane of the asteroid belt region but find that these fields were dominated by toroidal and radial components that periodically reversed every few hundred years (Turner & Sano 2008).”
Planet formation bursts at the borders of the dead zone in 2D numerical simulations of circumstellar disks (2009, background): “2 Another alternative is local ionization provided by the decay of the short-lived radioactive nuclide 26Al (Umebayashi & Nakano 2009), although Turner & Sano (2008) show that the free electrons given out by this low ionization source would quickly recombine on the surface of µm-sized dust grains.”