Dusty vortices in protoplanetary disks

Global two-dimensional simulations are used to study the coupled evolution of gas and solid particles in a Rossby unstable protoplanetary disk. The initial radial bump in density is unstable to the formation of Rossby waves, which roll up and break into anticyclonic vortices that gradually merge into a large-scale vortical structure persisting for more than 100 rotations. Conditions for the growth of such vortices may naturally appear at the outer edge of the "dead zone" of a protoplanetary disk where gas tends to pile up. We find that solid particles are captured by the vortices and change the evolution: (1) large particles rapidly sink toward the center of the vortices and increase the solid-to-gas ratio by an order of magnitude, (2) solid particles tend to reduce the lifetime of the vortices, and (3) solid particles are effectively confined in the vortices before they are dispersed by the Keplerian shear flow. These results confirm that in a minimum mass solar nebula, persistent vortices could be good places for the formation of the planetesimals or the rocky cores of gas giant planets as soon as particles reach boulder size.