A "no-drift" runaway pile-up of pebbles in protoplanetary disks in which midplane turbulence increases with radius

Abstract

A notable challenge of planet formation is to find a path to directly form planetesimals from small particles. We aim to understand how drifting pebbles pile up in a protoplanetary disk with a non-uniform turbulence structure. We consider a disk structure in which the midplane turbulence viscosity is increasing with radius in protoplanetary disks as in the outer region of a dead zone. We perform 1D diffusion-advection simulations of pebbles that include back-reaction (the inertia) to radial drift and vertical/radial diffusion of pebbles for a given pebble-to-gas mass flux. We report a new mechanism, the "no-drift" runaway pile-up, leading to a runaway accumulation of pebbles in disks, thus favoring the formation of planetesimals by streaming and/or gravitational instabilities. This occurs when pebbles drifting in from the outer disk and entering a dead zone experience a decrease in vertical turbulence. The scale height of the pebble subdisk then decreases, and for small enough values of the turbulence in the dead zone and high values of the pebble to gas flux ratio, the back-reaction of pebbles on gas leads to a significant decrease in their drift velocity and thus their progressive accumulation. This occurs when the ratio of the flux of pebbles to that of the gas is large enough so that the effect dominates over any Kelvin-Helmholtz shear instability. This process is independent of the existence of a pressure bump.

7 pages, 3 Figures, 1 Figure in Appendix; Accepted for publication in Astronomy & Astrophysics Letters (A&A Letters)

References in corpus (16)

• Particle Stirring in Turbulent Gas Disks: Including Orbital Oscillations
• Global simulations of protoplanetary disks with ohmic resistivity and ambipolar diffusion
• Planetesimal formation starts at the snow line
• How to form planetesimals from mm-sized chondrules and chondrule aggregates
• Grain Retention and Formation of Planetesimals near the Snow Line in MRI-driven Turbulent Protoplanetary Disks
• Planetesimal formation around the snow line in MRI-driven turbulent protoplanetary disks
• Formation of dust-rich planetesimals from sublimated pebbles inside of the snow line
• Can dead zones create structures like a transition disk?
• Particle dynamics in discs with turbulence generated by the vertical shear instability
• Gas and dust dynamics in starlight-heated protoplanetary disks
• An opening criterion for dust gaps in protoplanetary discs
• Temperature Structure in the Inner Regions of Protoplanetary Disks: Inefficient Accretion Heating Controlled by Nonideal Magnetohydrodynamics
• Gravitoviscous protoplanetary disks with a dust component. III. Evolution of gas, dust, and pebbles
• Planetesimal formation around the snow line. II. Dust or pebbles?
• Planetesimal formation around the snow line: I. Monte Carlo simulations of silicate dust pile-up in a turbulent disk
• Electron Heating and Saturation of Self-regulating Magnetorotational Instability in Protoplanetary Disks

Cited by in corpus (5)

• Forming pressure-traps at the snow-line to isolate isotopic reservoirs in the absence of a planet
• Planetesimal formation around the snow line. II. Dust or pebbles?
• Planetesimal formation around the snow line: I. Monte Carlo simulations of silicate dust pile-up in a turbulent disk
• Effects from different grades of stickiness between icy and silicate particles on carbon depletion in protoplanetary disks
• A "no-drift" runaway pile-up of pebbles in protoplanetary disks II. Characteristics of the resulting planetesimal belt