Turbulent Torques on Protoplanets in a Dead Zone


Dynamical migration of protoplanets seems likely to explain the observed distribution of extrasolar planets. Previous work on laminar disks predicts short migration times (less than the disk lifetime). This is a significant problem for the "core accretion" scenario, in which giant planets are thought to form from small, rocky protoplanetary cores in the disk. However, there have been recent suggestions that the turbulence providing accretion in protoplanetary disks might enhance migration by turning laminar migration into a random walk, possibly providing a solution to the short migration timescale. I will report the results of local, 3D simulations of MHD turbulence with quiescent "dead zones" of varying sizes at the midplane. I demonstrate that turbulent torques on a massless protoplanet at the midplane are strongly affected by the presence of dead zones, which considerably decrease the total turbulent torque on the planet. In all cases, the torques have a finite correlation time and are dominated by gas close to the planet. These results can be incorporated into statistical models for the survival of a population of protoplanets in a disk, allowing a better understanding of the nature of planet migration and survival.

American Astronomical Society Meeting Abstracts