HALL EFFECT CONTROLLED GAS DYNAMICS IN PROTOPLANETARY DISKS. II. FULL 3D SIMULATIONS TOWARD THE OUTER DISK

By Xue-Ning Bai. 2014

137 citations recorded by the source corpus.

We perform three-dimensional stratified shearing-box magnetohydrodynamic (MHD) simulations on the gas dynamics of protoplanetary disks with a net vertical magnetic flux of Bz0. All three nonideal MHD effects, Ohmic resistivity, the Hall effect, and ambipolar diffusion, are included in a self-consistent manner based on equilibrium chemistry. We focus on regions toward outer disk radii, from 5 to 60 AU, where Ohmic resistivity tends to become negligible, ambipolar diffusion dominates over an extended region across the disk height, and the Hall effect largely controls the dynamics near the disk midplane. We find that at around R = 5 AU the system launches a laminar or weakly turbulent magnetocentrifugal wind when the net vertical field Bz0 is not too weak. Moreover, the wind is able to achieve and maintain a configuration with reflection symmetry at the disk midplane. The case with anti-aligned field polarity () is more susceptible to the magnetorotational instability (MRI) when Bz0 decreases, leading to an outflow oscillating in radial directions and very inefficient angular momentum transport. At the outer disk around and beyond R = 30 AU, the system shows vigorous MRI turbulence in the surface layer due to far-UV ionization, which efficiently drives disk accretion. The Hall effect affects the stability of the midplane region to the MRI, leading to strong/weak Maxwell stress for aligned/anti-aligned field polarities. Nevertheless, the midplane region is only very weakly turbulent in both cases. Overall, the basic picture is analogous to the conventional layered accretion scenario applied to the outer disk. In addition, we find that the vertical magnetic flux is strongly concentrated into thin, azimuthally extended shells in most of our simulations beyond 15 AU, leading to enhanced radial density variations know as zonal flows. Theoretical implications and observational consequences are briefly discussed.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/bccdcebbcac6cbd0fa7579073bd51ed462b1823e

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In Astronomy and Astrophysics

1. Xue-Ning Bai
2. G. Herczeg
3. L. Hartmann
4. N. Calvet
5. R. Nelson
6. N. J. Turner
7. Oliver Gressel
8. C. McNally

Citations in the corpus

• Accretion onto Pre-Main-Sequence Stars (2016, background): “Bai (2014) has argued that this is the dominant mode of mass and angular momentum transport in T Tauri disks at radii of ∼1–10 AU, with thermal and nonthermal activation of MRI at smaller and larger radii, respectively.”
• GLOBAL SIMULATIONS OF PROTOPLANETARY DISKS WITH OHMIC RESISTIVITY AND AMBIPOLAR DIFFUSION (2015, methodology): “Shearing box simulations presented by Lesur et al. (2014) and Bai (2014) show that when Ω · B > 0, the Hall effect leads to the amplification of the horizontal magnetic fields within approximately two scale heights of the disk midplane, and the generation of a large scale Maxwell stress through…”
• Global Simulations of the Inner Regions of Protoplanetary Disks with Comprehensive Disk Microphysics (2017, methodology): “This is consistent with previous local simulations (Bai 2014, 2015), and for a given vertical field, the amplification factor also depends on the assumed grain abundance (e.g., see Lesur et al. 2014; Simon et al. 2015; Xu & Bai 2016 where different grain abundances are adopted).”