[P-PS04] 惑星科学

[PPS04-P32] Scaling Laws of Dust Clumps Formed by Streaming Instability and Dust Growth Therein

和田 航汰¹、*田中 秀和¹、冨永 遼佑² (1.東北大学理学研究科、2.東京科学大学理学院)

キーワード：

惑星形成、微惑星形成、ストリーミング不安定性、ダスト成長

Planetesimal formation is the most challenging problem in planetary formation theory. The most promising model involves planetesimal formation through the gravitational instability of dense dust clumps created by streaming instability in the protoplanetary disk. Previous simulations of streaming instability primarily focused on maximum dust density and debated whether it exceeds the Roche density required to trigger gravitational instability. This study, in contrast, aims to clarify the overall picture of streaming instability and its nonlinear properties by examining the size of dust density structures and dust collision velocities. We performed extensive two-dimensional unstratified simulations of streaming instability, varying the Stokes number and the dust-to-gas ratio. We also performed simulations with a dust size distribution. By analyzing our simulation results of streaming instability using two-body correlation functions, we discovered that the size of the dust clump structure is proportional to the average drift speed of dust relative to the gas. We derived an empirical formula for this average relative drift speed. Furthermore, we analyzed the collision velocity distribution and collisional mass flux to derive empirical expressions for these quantities. We demonstrated that the collision velocity distribution can be expressed as a universal formula independent of parameters when scaled by the average relative drift speed. The empirical expression for the collisional mass flux yields the dust growth time, consistent with previous studies. Simulations with a size distribution suggest that the distribution evolves toward narrower ranges as a result of dust growth.