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Transport processes play crucial role in the global evolution of
protoplanetary disks. Likely, they are responsible for the
presence of crystalline silicate dust in outer disk regions
and in comets and meteoritic bodies in our solar
system, and non-thermal broadening of the
observed molecular lines. However, the
influence of transport phenomena on the chemical evolution of
protoplanetary disks has hardly been studied in detail. In my
presentation, I will talk about the importance of turbulent diffusion for
disk
chemical evolution. Briefly, the time-dependent chemistry over 5 Myr
is modeled, using a T Tau disk structure with vertical temperature
gradient, a
gas-grain chemical network with surface chemistry, and several chemical
models with and without turbulent mixing included.
Overall, the turbulent diffusion in both radial and vertical directions does
not affect significantly the abundances of many simple molecules and ions
produced by fast photoreactions in the disk, but is very important for
more complex
molecules and deuterated species whose evolution is governed by surface
chemistry. Particularly, it is demonstrated that the 2D mixing modeling
results can
explain the puzzling "CO depletion problem"---a large amount of CO gas at
T<15 K in
the DM Tau disk.
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