Two key parameters controlling particle clumping caused by streaming instability in the dead-zone dust layer of a protoplanetary disk

TL;DR

This study identifies two key parameters, the Stokes number and dust particle column density, that determine dust particle clumping due to streaming instability in the dead zone of protoplanetary disks, confirmed through 3D numerical simulations.

Contribution

The paper introduces a new classification scheme using two parameters to predict dust clumping behavior in protoplanetary disks, enhancing understanding of planetesimal formation conditions.

Findings

Dust clumping magnitude is similar across different disk models with identical parameter sets.

The proposed parameters effectively classify the development of particle clumping.

Simulation results support the parameters' role in predicting dust behavior.

Abstract

The streaming instability and Kelvin--Helmholtz instability are considered the two major sources causing clumping of dust particles and turbulence in the dust layer of a protoplanetary disk as long as we consider the dead zone where the magneto-rotational instability does not grow. Extensive numerical simulations have been carried out in order to elucidate the condition for the development of particle clumping caused by the streaming instability. In this paper, a set of two parameters suitable for classifying the numerical results is proposed. One is the Stokes number that has been employed in previous works and the other is the dust particle column density that is nondimensionalized using the gas density in the midplane, Keplerian angular velocity, and difference between the Keplerian and gaseous orbital velocities. The magnitude of dust clumping is a measure of the behavior of the dust layer. Using three-dimensional numerical simulations of dust particles and gas based on Athena code v. 4.2, it is confirmed that the magnitude of dust clumping for two disk models are similar if the corresponding sets of values of the two parameters are identical to each other, even if the values of the metallicity (i.e., the ratio of the columns density of the dust particles to that of the gas) are different.