Oral Presentation
Accretion across scales: Streamers, surface-layer transport, and rapid replenishment in young protoplanetary discs
Presenter: Christian G. Holm (Centre for Star and Planet Formation, Globe Institute, University of Copenhagen)
How young protoplanetary discs acquire mass from their turbulent cloud environment, whether through midplane or polar infall and whether the mass delivery is steady or burst-like, remains uncertain. Using the adaptive mesh refinement framework DISPATCH, we investigate nine stellar systems with 3D ideal magnetohydrodynamic zoom-in simulations of disc formation and evolution in a dynamic molecular cloud. While resolving disc structures down to approximately 0.8 au, we obtain disc sizes in the order of 100 au. During the ~10^5 yr evolution, accretion onto the protostar significantly fluctuates around ~10^(-5) M_sun/yr, maintaining disc to star mass ratios below 10 %. Disc mass is replenished on timescales of 10 kyr. On the large scale (> 1000 au), anisotropic mass inflow is supplied by transient dense streamers at mass accretion rates comparable to the stellar accretion. The streamer-disc interaction can temporarily halve the disc size and reduce disc masses by ~40%. Under the assumption that the outer regions of young discs are well-ionised, our results indicate that these young discs are unlikely to support early planet formation because of high disc replenishment rates and disruptive streamer infall.
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