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Title: Magnetic coupling in the disks around young gas giant planets

We examine the conditions under which the disks of gas and dust orbiting young gas giant planets are sufficiently conducting to experience turbulence driven by the magneto-rotational instability. By modeling the ionization and conductivity in the disk around proto-Jupiter, we find that turbulence is possible if the X-rays emitted near the Sun reach the planet's vicinity and either (1) the gas surface densities are in the range of the minimum-mass models constructed by augmenting Jupiter's satellites to solar composition, while dust is depleted from the disk atmosphere, or (2) the surface densities are much less, and in the range of gas-starved models fed with material from the solar nebula, but not so low that ambipolar diffusion decouples the neutral gas from the plasma. The results lend support to both minimum-mass and gas-starved models of the protojovian disk. (1) The dusty minimum-mass models have internal conductivities low enough to prevent angular momentum transfer by magnetic forces, as required for the material to remain in place while the satellites form. (2) The gas-starved models have magnetically active surface layers and a decoupled interior 'dead zone'. Similar active layers in the solar nebula yield accretion stresses in the range assumed in constructing themore » circumjovian gas-starved models. Our results also point to aspects of both classes of models that can be further developed. Non-turbulent minimum-mass models will lose dust from their atmospheres by settling, enabling gas to accrete through a thin surface layer. For the gas-starved models it is crucial to learn whether enough stellar X-ray and ultraviolet photons reach the circumjovian disk. Additionally, the stress-to-pressure ratio ought to increase with distance from the planet, likely leading to episodic accretion outbursts.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
  2. Department of Earth Sciences and Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong)
  3. Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan)
Publication Date:
OSTI Identifier:
22351377
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 783; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; AMBIPOLAR DIFFUSION; ANGULAR MOMENTUM TRANSFER; COUPLING; DENSITY; EMISSION; INSTABILITY; JUPITER PLANET; LAYERS; MAGNETOHYDRODYNAMICS; MASS; SIMULATION; SOLAR NEBULA; STRESSES; SURFACES; TURBULENCE; ULTRAVIOLET RADIATION; X RADIATION