The nature of Turbulence in Planet Formation: Magnetorotational and Baroclinic Instability

Hubert Klahr

Turbulence in protoplanetary disks diffuses small solid material, leads to collisions among larger objects, concentrates boulders promoting planetesimal formation via gravity and also has an impact on planet migration. Despite the importance of turbulence, its nature is not completely understood so far. In certain regions of the disk the gas is sufficiently ionized for Magneto-Hydrodynamics to lead to turbulence. Other regions being too cold or dusty could now either be dead zones without turbulence or develop a different kind of instability. Realistic radial entropy gradients and thermal diffusion times in typical accretion disks around young stars can lead to baroclinic instability and the formation of vortices and the generation of turbulent viscosity. I summarize the state of field of baroclinic instability in accretion disks and show latest results from numerical simulations.