Streaming instability of multiple particle species

II. Numerical convergence with increasing particle number

¹ Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden
e-mail: noemi.schaffer@astro.lu.se
² Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5–7, 1350 Copenhagen, Denmark

Received: 1 March 2021
Accepted: 29 June 2021

Abstract

The streaming instability provides an efficient way of overcoming the growth barriers in the initial stages of the planet formation process. Considering the realistic case of a particle size distribution, the dynamics of the system is altered compared to the outcome of single size models. In order to understand the outcome of the multispecies streaming instability in detail, we perform a large parameter study in terms of particle number, particle size distribution, particle size range, initial metallicity, and initial particle scale height. We study vertically stratified systems and determine the metallicity threshold for filament formation. We compare these with a system where the initial particle distribution is unstratified and find that its evolution follows that of its stratified counterpart. We find that a change in the particle number does not result in significant variation in the efficiency and timing of filament formation. We also see that there is no clear trend for how varying the size distribution in combination with the particle size range changes the outcome of the multispecies streaming instability. Finally, we find that an initial metallicity of Z_init = 0.005 and Z_init = 0.01 both result in similar critical metallicity values for the start of filament formation. Our results show that the inclusion of a particle size distribution into streaming instability simulations, while changing the dynamics as compared to mono-disperse systems, does not result in overall unfavorable conditions for solid growth. We attribute the subdominant role of multiple species to the high-density conditions in the midplane, conditions under which linear stability analysis also predict little difference between single and multiple species.