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Title: Efficiency of particle trapping in the outer regions of protoplanetary disks

We investigate the strength of axisymmetric local pressure maxima (zonal flows) in the outer regions of protoplanetary disks, where ambipolar diffusion reduces turbulent stresses driven by the magnetorotational instability. Using local numerical simulations we show that in the absence of net vertical magnetic fields, the strength of turbulence in the ambipolar dominated region of the disk is low and any zonal flows that are present are weak. For net fields strong enough to yield observed protostellar accretion rates, however, zonal flows with a density amplitude of 10%-20% are formed. These strengths are comparable to those seen in simulations of ideal MHD disk turbulence. We investigate whether these zonal flows are able to reverse the inward radial drift of solids, leading to prolonged and enhanced concentration as a prelude to planetesimal formation. For commonly assumed mean surface density profiles (surface density Σ∝r {sup –1/2} or steeper) we find that the predicted perturbations to the background disk profile do not correspond to local pressure maxima. This is a consequence of radial width of the simulated zonal flows, which is larger than was assumed in prior analytic models of particle trapping. These larger scale flows would only trap particles for higher amplitude fluctuationsmore » than observed. We conclude that zonal flows are likely to be present in the outer regions of protoplanetary disks and are potentially large enough to be observable, but are unlikely to lead to strong particle trapping.« less
Authors:
 [1] ;  [2]
  1. Department of Space Studies, Southwest Research Institute, Boulder, CO 80302 (United States)
  2. JILA, University of Colorado and NIST, 440 UCB, Boulder, CO 80309-0440 (United States)
Publication Date:
OSTI Identifier:
22351531
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 784; 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; ABUNDANCE; ACCRETION DISKS; AMBIPOLAR DIFFUSION; AXIAL SYMMETRY; COMPUTERIZED SIMULATION; CONCENTRATION RATIO; DENSITY; DISTURBANCES; FLUCTUATIONS; INSTABILITY; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PERTURBATION THEORY; PLANETS; PROTOPLANETS; SATELLITES; STRESSES; TRAPPING; TURBULENCE