Dust evolution in protoplanetary accretion disks.
W. Schmitt, T. Henning, R. Mucha;
AaA, 1997, 325, 569
ABSTRACT:The time evolution of dust particles in circumstellar disk-like structures around protostars and young stellar objects was investigated.
For
the first time, we coupled the dust evolution directly to the evolution of
the disk and followed the influence of opacity changes due to collisional
aggregation on the dynamics of the disk.
For that purpose, we numerically
simulated the dynamical evolution of a turbulent protoplanetary accretion disk
described by a time-dependent one-dimensional (radial) "alpha" model.
Within
this model, the growth of dust grains due to coagulation was calculated by
solving numerically the non-linear Smoluchowski equation.
As physical
processes leading to relative velocities between the grains, Brownian motion,
turbulence, and drift motion were taken into account.
In contrast to other
studies, we especially considered particle-cluster agglomeration (PCA) as
growth mode but also included cluster-cluster agglomeration (CCA) into our
considerations.
For time periods of 100 years and disk radii up to 100AU, the mass
distributions of coagulated dust grains were calculated.
From these mass spectra,
we determined the corresponding Rosseland mean dust opacities.
The
variations of the dust grain opacity drive changes in the energetic structure of
the protoplanetary disk which again influences the accretion process
itself.
Our results show three evolutionary stages of the PCA process.
For CCA
particles, there is no dust growth after the disappearance of the smallest
grains.
The different characteristic timescales for the coagulation at
different radii result in the restructuring of the dust region of the
protoplanetary disks.
Significant changes in the thermal and optical structure of
the disk occur.
KEYWORDS: accretion disks, hydrodynamics, turbulence, methods: numerical, solar system: formation, planetary system
PERSOKEY:dust, size distribution, ,
CODE: schmitt97