(Abridged) Numerical magnetohydrodynamic (MHD) simulations of a turbulent
solar nebula are used to study the growth of dust mantles swept up by
chondrules. A small neighborhood of the solar nebula is represented by an
orbiting patch of gas at a radius of 3 AU, and includes vertical stratification
of the gas density. The differential rotation of the nebular gas is replaced by
a shear flow. Turbulence is driven by destabilization of the flow as a result
of the magnetorotational instability (MRI), whereby magnetic field lines
anchored to the gas are continuously stretched by the shearing motion. A
passive contaminant mimics small dust grains that are aerodynamically well
coupled to the gas, and chondrules are modeled by Lagrangian particles that
interact with the gas through drag. Whenever a chondrule enters a region
permeated by dust, its radius grows at a rate that depends on the local dust
density and the relative velocity between itself and the dust. The local dust
abundance decreases accordingly. Different chondrule volume densities lead to
varying depletion and rimmed-chondrule size growth times. Most of the dust
sweep-up occurs within 1 gas scale height of the nebula midplane. Chondrules
can reach their asymptotic radius in 10 to 800 years. The vertical variation of
nebula turbulent intensity results in a moderate dependence of mean
rimmed-chondrule size with nebula height. The technique used here could be
combined with Monte Carlo (MC) methods that include the physics of dust
compaction, in a self-consistent MHD-MC model of dust rim growth around
chondrules in the solar nebula.Comment: 33 pages, 9 figures. Icarus, in pres
