PI: Henrik Latter

Protoplanetary disks are the birth environments for planetary systems, and hence of life more generally. They are also highly complex and dynamic magnetohydrodynamic (MHD) flows, containing a hot turbulent inner region close to the star and a cooler laminar region further away. The work carried out under DiRAC grant dp316, building on previous awards, investigates the flows of both dust and gas in this region, in particular, (a) around and through the interface between laminar and turbulence regions and (b) how any winds launched entrain small solid particles, leading to their radial transport and potentially thermal (re-) processing. 

An important result we find is the ‘porosity’ of the boundary between laminar and turbulent regions. Despite the presence of a pressure bump, solids can drift through it into the inner disk due to its fluctuating nature and a complex poloidal flow and current system around it. This can be observed in the two panels, where only the dust density it plotted. The pressure bump is at a radius slightly greater than 4 (in code units). Smaller dust is also entrained in a weak outflow. This porosity of the dead/active zone boundary complicates theories of planet formation that rely on the reliable build-up of solid material in the dead zone.

Figure: A snapshot of a simulation of the dust in a protoplanetary disk seen edge-on. Left panel plots the dust to gas ratio for 50mm particles; the right panel plots that of 5mm particles. The dead zone edge is at r=4 in code units, which can be mapped to ~1 AU.