Vortices in Protoplanetary Disks

We use a high order accuracy spectral code to carry out two-dimensionaltime-dependent numerical simulations of vortices in accretion disks. Inparticular, we examine the stability and the life time of vortices incircumstellar disks around young stellar objects. The results show thatcyclonic vortices dissipate quickly, while anticyclonic vortices can survive inthe flow for many orbits. When more than one vortex is present, theanticyclonic vortices interact through vorticity waves and merge together toform larger vortices. The decay time of anticyclonic vortices is of the orderof 30-60 orbital periods (for a viscosity parameter alpha = 1.e-4), which issufficiently long to allow heavy dust particles to rapidly concentrate in thecore of anticyclonic vortices in protoplanetary disks. This dust concentrationincreases the local density of centimeter-size grains, thereby favoring theformation of larger scale objects which are then capable of efficientlytriggering a gravitational instability. The relatively long-lived vorticesfound in this work may therefore play a key role in the formation process ofgiant planets.Comment: The Astrophysical Journal, in pres