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Planetesimal and Protoplanet Dynamics in a Turbulent Protoplanetary Disk: Ideal Unstratified Disks

Yang, Chao-Chin LU ; Mac Low, Mordecai-Mark and Menou, Kristen (2009) In The Astrophysical Journal 707(2). p.1233-1246
Abstract
The dynamics of planetesimals and planetary cores may be strongly influenced by density perturbations driven by magneto-rotational turbulence in their natal protoplanetary gas disks. Using the local shearing box approximation, we perform numerical simulations of planetesimals moving as massless particles in a turbulent, magnetized, unstratified gas disk. Our fiducial disk model shows turbulent accretion characterized by a Shakura-Sunyaev viscosity parameter of α ~ 10^-2, with rms density perturbations of ~10%. We measure the statistical evolution of particle orbital properties in our simulations including mean radius, eccentricity, and velocity dispersion. We confirm random walk growth in time of all three properties, the first time that... (More)
The dynamics of planetesimals and planetary cores may be strongly influenced by density perturbations driven by magneto-rotational turbulence in their natal protoplanetary gas disks. Using the local shearing box approximation, we perform numerical simulations of planetesimals moving as massless particles in a turbulent, magnetized, unstratified gas disk. Our fiducial disk model shows turbulent accretion characterized by a Shakura-Sunyaev viscosity parameter of α ~ 10^-2, with rms density perturbations of ~10%. We measure the statistical evolution of particle orbital properties in our simulations including mean radius, eccentricity, and velocity dispersion. We confirm random walk growth in time of all three properties, the first time that this has been done with direct orbital integration in a local model. We find that the growth rate increases with the box size used at least up to boxes of eight scale heights in horizontal size. However, even our largest boxes show velocity dispersions sufficiently low that collisional destruction of planetesimals should be unimportant in the inner disk throughout its lifetime. Our direct integrations agree with earlier torque measurements showing that type I migration dominates over diffusive migration by stochastic torques for most objects in the planetary core and terrestrial planet mass range. Diffusive migration remains important for objects in the mass range of kilometer-sized planetesimals. Discrepancies in the derived magnitude of turbulence between local and global simulations of magneto-rotationally unstable disks remains an open issue, with important consequences for planet formation scenarios. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
accretion accretion disks methods: numerical MHD planetary systems: formation planetary systems: protoplanetary disks turbulence
in
The Astrophysical Journal
volume
707
issue
2
pages
1233 - 1246
publisher
University of Chicago Press
external identifiers
  • Scopus:72949105582
DOI
10.1088/0004-637X/707/2/1233
language
English
LU publication?
no
id
d41f6f75-711e-4942-b6cd-337262395170 (old id 4361482)
date added to LUP
2014-03-20 16:51:09
date last changed
2016-10-13 04:44:58
@misc{d41f6f75-711e-4942-b6cd-337262395170,
  abstract     = {The dynamics of planetesimals and planetary cores may be strongly influenced by density perturbations driven by magneto-rotational turbulence in their natal protoplanetary gas disks. Using the local shearing box approximation, we perform numerical simulations of planetesimals moving as massless particles in a turbulent, magnetized, unstratified gas disk. Our fiducial disk model shows turbulent accretion characterized by a Shakura-Sunyaev viscosity parameter of α ~ 10^-2, with rms density perturbations of ~10%. We measure the statistical evolution of particle orbital properties in our simulations including mean radius, eccentricity, and velocity dispersion. We confirm random walk growth in time of all three properties, the first time that this has been done with direct orbital integration in a local model. We find that the growth rate increases with the box size used at least up to boxes of eight scale heights in horizontal size. However, even our largest boxes show velocity dispersions sufficiently low that collisional destruction of planetesimals should be unimportant in the inner disk throughout its lifetime. Our direct integrations agree with earlier torque measurements showing that type I migration dominates over diffusive migration by stochastic torques for most objects in the planetary core and terrestrial planet mass range. Diffusive migration remains important for objects in the mass range of kilometer-sized planetesimals. Discrepancies in the derived magnitude of turbulence between local and global simulations of magneto-rotationally unstable disks remains an open issue, with important consequences for planet formation scenarios.},
  author       = {Yang, Chao-Chin and Mac Low, Mordecai-Mark and Menou, Kristen},
  keyword      = {accretion accretion disks methods: numerical MHD planetary systems: formation planetary systems: protoplanetary disks turbulence},
  language     = {eng},
  number       = {2},
  pages        = {1233--1246},
  publisher    = {ARRAY(0x77c28c8)},
  series       = {The Astrophysical Journal},
  title        = {Planetesimal and Protoplanet Dynamics in a Turbulent Protoplanetary Disk: Ideal Unstratified Disks},
  url          = {http://dx.doi.org/10.1088/0004-637X/707/2/1233},
  volume       = {707},
  year         = {2009},
}