Transport of Dust Grains in Turbulent Molecular Clouds
B. R. Ragot;
ApJ, 1998, 498, 757
ABSTRACT:Recently, F.P.
Pijpers has estimated anew the average residence
time of dust grains in turbulent molecular clouds, modeling the grains'
dynamics as a random walk along turbulent eddies of a Kolmogorov energy
spectrum, with distribution versus size similar to that of the
clumps.
Implicitly, he assumed that this results in a diffusive transport process (the
spreading of the dust grains < Delta r2(t)> increasing linearly with time t), and
obtained a residence time scaling almost as the Reynolds number of the flow, and
hence much longer than previous estimates.
Following the same random walk
model, the grains are shown here to be transported anomalously quickly (<
Delta r2(t)> ~ t alpha with alpha >= 3), and a much shorter time is found,
scaling as the Reynolds number to some negative power.
This might indicate the
need to take into account the organization of the turbulent structures when
computing the transport exponent alpha .
KEYWORDS: ism: dust, extinction, ism: clouds, turbulence
PERSOKEY:turbulence, dust, size distribution, ,
CODE: ragot98