Protostars and Planets VI, Heidelberg, July 15-20, 2013
RADIAL ACCUMULATION AND TURBULENT CONCENTRATION OF THE DUST BOULDERS AT THE RADIAL PRESSURE BUMP IN PROTOPLANETARY DISKS
Taki, Tetsuo (Titech)
Fujimoto, Masaki (ISAS/JAXA, ELSI/Titech)
Ida, Shigeru (ELSI/Titech)
In the process of planetesimal formation, spiral-in of dust boulders toward the host star is the most serious difficulty. One of the mechanisms to halt the spiral-in is a radial pressure bump in the disk, at which the boundary between local super/sub-Keplerian flow exists. However, according to accumulation of dust boulders at the super/sub-Keplerian transition point, the dust frictional force alters the gas density profile (e.g., Kato et al., 2012). We think that accumulation processes of the dust boulders at the pressure bump, which is simply borne by the gas azimuthal velocity profile. To investigate the time evolution of dust and gad density distributions at once, we conduct the local 1-D and 2-D hybrid simulations, which take into account the backreaction from the dust to the gas consistently. In 1-D simulations, we found that the gas density distribution is seriously deformed as the dust accumulates at pressure bump in the case with backreaction. The dust density distribution is radially expanded around the boundary between super/sub-Keplerian flow quickly. Finally, the dust boulders resume the inward drifts, and their density distribution achieves the gradual peak in the radial direction. Then the maximum dust-to-gas density ratio is just about unity. In 2-D simulations, we confirm the driving of streaming instability in the one-dimensionally-dense region of dust, formed by the radial pressure bump. Though, The dust-to-gas density ratios, which is enhanced by the SI, is too small to drive the gravitational instability, and the pressure bump is not able to maintain the halting of the dust boulders as is the case with 1-D simulations. Therefore, we conclude that the halting mechanism of pressure bump is not able to form the planetesimals very well by itself. Then we suggest the possibility that the effect of the maintenance or restoration to the pressure bump might increase the dust density and form the planetesimals via gravitational instability.
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