Nonlinear Outcome of Coagulation Instability in Protoplanetary Disks I: First Numerical Study of Accelerated Dust Growth and Dust Concentration at Outer Radii

TL;DR

This paper presents the first numerical study of coagulation instability in protoplanetary disks, showing it can concentrate dust and accelerate growth, potentially aiding planetesimal formation at outer radii.

Contribution

It demonstrates through simulations that coagulation instability can cause dust concentration and growth acceleration without requiring backreaction or fragmentation effects.

Findings

Coagulation instability leads to dust ring formation.

Dust growth is accelerated, reaching $ au_s=1$ at outer radii.

Dust concentration occurs even without backreaction or fragmentation.

Abstract

Our previous linear analysis presents a new instability driven by dust coagulation in protoplanetary disks. The coagulation instability has the potential to concentrate dust grains into rings and assist dust coagulation and planetesimal formation. In this series of papers, we perform numerical simulations and investigate nonlinear outcome of coagulation instability. In this paper (Paper I), we first conduct local simulations to demonstrate the existence of coagulation instability. Linear growth observed in the simulations is in good agreement with the previous linear analysis. We next conduct radially global simulations to demonstrate that coagulation instability develops during the inside-out disk evolution due to dust growth. To isolate the various effects on dust concentration and growth, we neglect effects of backreaction to a gas disk and dust fragmentation in Paper I. This simplified simulation shows that either of backreaction or fragmentation is not prerequisite for local dust concentration via the instability. In most runs with weak turbulence, dust concentration via coagulation instability overcomes dust depletion due to radial drift, leading to the formation of multiple dust rings. The nonlinear development of coagulation instability also accelerates dust growth, and the dimensionless stopping time $\tau_{\mathrm{s}}$ reaches unity even at outer radii (>10 au). Therefore, coagulation instability is one promising process to retain dust grains and to accelerate dust growth beyond the drift barrier.