Planet formation: First steps from first principles

Phil Armitage (U. of Colorado)

The first steps in planet formation - growing from dust to km-scale planetesimals - are poorly understood, because the physics in this size regime is dominated by aerodynamic coupling to the turbulent protoplanetary disk. I will describe efforts to remedy this situation using a new generation of simulations of disk turbulence. The simulations include the non-ideal MHD processes that are of critical importance in cold protoplanetary disks, and take advantage of the Athena code's scalability to over 100,000 processor cores. Results I will highlight include evidence for the growth and dynamical role of large-scale magnetic fields, predictions for turbulent line broadening in disk atmospheres that may be observable with ALMA, and consequences of disk dead zones for the growth of massive planets.