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Rethinking Dust Concentration in Protoplanetary Disks with Underwater Sand Ripples

Presentation #615.10 in the session Planet Formation Theory.

Published onApr 03, 2024
Rethinking Dust Concentration in Protoplanetary Disks with Underwater Sand Ripples

The hydrodynamic behavior of dust in protoplanetary disks, key during the initial stages of planet formation, remains riddled with questions. In particular, there is ambiguity regarding the physical processes that can concentrate dust to densities sufficient for planetesimal formation. Drawing upon the analogy of underwater sand ripples, I will introduce a new linear, axisymmetric instability that may resolve this question. The diffusive instability can reorganize a turbulent dust patch in the mid-plane of a protoplanetary disk into azimuthally elongated, high density filaments, provided diffusivity decreases sufficiently fast with increasing dust loading — a premise supported by our numerical simulations of protoplanetary disks where dust-gas interactions self-generate turbulent diffusion. I will discuss the diffusion instability’s role in broader planetesimal formation theory, including its relationship to the streaming instability, and provide predictions for characteristic sizes of initial planetesimals that are of order 100km, an estimate consistent with Asteroid Belt data.

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