Speaker
Description
Despite its importance for star and planet formation, the physical process(es) that drive disk accretion remain frustratingly unclear. The magnetorotational instability is questioned both theoretically and observationally and disk winds are increasingly invoked. I will describe how the evolution of gas disk sizes from Class I to Class II indicates that some mechanism produces significant disk spreading (i.e., angular momentum transport within the disk) during the Class II phase. I will also show results from high resolution mid-infrared spectroscopy of a Class I source that may provide evidence for an alternative angular momentum transport mechanism, “surface accretion flows,” which have been reported in MHD simulations of magnetized disks.
