Global simulations of protoplanetary disks with OHMIC resistivity and ambipolar diffusion

Journal Article · Tue Mar 10 00:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/801/2/84· OSTI ID:22882685

Gressel, Oliver; McNally, Colin P. ^[1]; Turner, Neal J. ^[2]

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1. Niels Bohr International Academy, The Niels Bohr Institute, Blegdamsvej 17, DK-2100, Copenhagen Ø (Denmark)
2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

Protoplanetary disks (PPDs) are believed to accrete onto their central T Tauri star because of magnetic stresses. Recently published shearing box simulations indicate that Ohmic resistivity, ambipolar diffusion (AD) and the Hall effect all play important roles in disk evolution. In the presence of a vertical magnetic field, the disk remains laminar between 1–5 AU, and a magnetocentrifugal disk wind forms that provides an important mechanism for removing angular momentum. Questions remain, however, about the establishment of a true physical wind solution in the shearing box simulations because of the symmetries inherent in the local approximation. We present global MHD simulations of PPDs that include Ohmic resistivity and AD, where the time-dependent gas-phase electron and ion fractions are computed under FUV and X-ray ionization with a simplified recombination chemistry. Our results show that the disk remains laminar, and that a physical wind solution arises naturally in global disk models. The wind is sufficiently efficient to explain the observed accretion rates. Furthermore, the ionization fraction at intermediate disk heights is large enough for magneto-rotational channel modes to grow and subsequently develop into belts of horizontal field. Depending on the ionization fraction, these can remain quasi-global, or break-up into discrete islands of coherent field polarity. The disk models we present here show a dramatic departure from our earlier models including Ohmic resistivity only. It will be important to examine how the Hall effect modifies the evolution, and to explore the influence this has on the observational appearance of such systems, and on planet formation and migration.

• OSTI ID: 22882685
• Journal Information: Astrophysical Journal, Vol. 801, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
AMBIPOLAR DIFFUSION
ANGULAR MOMENTUM
COMPUTERIZED SIMULATION
ELECTRONS
HALL EFFECT
IONIZATION
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MATHEMATICAL SOLUTIONS
MIGRATION
PLANETS
PROTOPLANETS
RECOMBINATION
STELLAR WINDS
STRESSES
SYMMETRY
T TAURI STARS
TIME DEPENDENCE