Grain growth in turbulent protoplanetary accretion disks
H. Mizuno, W. J. Markiewicz, H. J. Voelk;
AaA, 1988, 195, 183
ABSTRACT:The process of coagulation of dust grains in spatially uniform turbulent gas, where at the low mass end of the grain size spectrum small
interstellar grains are assumed to be added continuously, was studied.
The
turbulence-induced collision velocity between two grains was calculated including a
finite inner scale of the turbulence, and the asymptotic mass spectrum and
dust opacity were obtained.
These calculations were applied to the case of
a rotating protostellar nebula, where the central object accretes mass
through a turbulent accretion disk, which in turn is fed by material from an
extended collapsing outer envelope.
It is shown that the grain opacity
initially increases with time, keeping the disk convectively turbulent; later
on, even though the disk is fed by small particles, convective instability
ceases due to the decrease of the opacity on account of grain growth.
During
the following quiet episode, the freshly added interstellar grains can
increase the disk opacity again until convection restarts.
It is shown that
planetesimal formation might be possible through sedimentation during the laminar
phases.
KEYWORDS: accretion disks, cosmic dust, cosmology, particle size distribution, protoplanets, turbulence effects, angular momentum, extrasolar planets, laminar flow, nebulae, planetary evolution, solar system, spectrum analysis
PERSOKEY:turbulence, dust, size distribution, ,
CODE: mizuno88