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J. A. Barranco, P. S. Marcus (University of California, Berkeley)
Understanding how millimeter-sized dust grains agglomerate to become kilometer-sized, self-gravitating ``planetesimals'' is a key problem in planet formation. One theory is that the dust grains settle into the mid-plane of the protoplanetary disk (orbiting around the newly forming star) until they reach a critical density that triggers a gravitational instability to clumping. However, turbulence within the disk is likely to stir up the dust grains and prevent them from reaching this critical density. We examine the role of 3D vortices within the protoplanetary disk in aiding the agglomeration of dust grains. We have shown that gas-drag creates an attracting basin within the vortices in which the grains accumulate. Some of the questions we will answer with our novel numerical simulations are: (1) Are 3D vortices robust and long-lived structures? Do smaller vortices merge to form larger vortices the way jovian vortices do? (2) What is the rate at which vortices capture dust grains, as a function of grain size and/or drag parameters? Are vortices effective at preventing grains from viscously spirally into the protostar? (3) Do 3D vortices reduce turbulence in their interiors (the way laboratory and jovian vortices do) which would allow captured grains to settle into the mid-plane of the disk? (4) At what point do the captured grains become gravitationally unstable to clumping? What is the nonlinear development of this instability? We would like to thank NASA, NSF, and the Berkeley Center for Integrative Planetary Sciences for supporting this research.