Magnetic activity and the separation of dust from gas
Seminar Room 1, Newton Institute
From the starlight scattered and reprocessed by protostellar disks we know that micron-sized dust grains remain suspended in the disk atmospheres for several million years. At the same time, measurements at millimeter wavelengths indicate that some particles inside the disks have grown to the size of pebbles. Surely planet formation is underway. Yet according to coagulation models, if the disk gas were laminar, the dust would quickly grow and settle out, leaving the atmosphere optically thin. On the other hand, turbulence at the levels suggested by disk evolutionary timescales would lead to collisional disruption, halting the growth of larger bodies. I will discuss how these difficulties can be resolved if the disk has a magnetically-active, turbulent atmosphere combined with a midplane dead zone.