Streaming instability phase space. (a) The ratio of the surface densities of grown dust to gas, ξ_d2g, as a function of the Stokes number. The pink and dashed black lines mark the critical values above which the streaming instability develops according to C. C. Yang et al. (2017) and R. Li & A. N. Youdin (2021), respectively. (b) The ratio of the volume densities of grown dust to gas, ζ, as a function of Stokes number. The solid black line indicates the critical values for the streaming instability according to R. Li & A. N. Youdin (2021). The data of our model are overlaid with filled circles, with blue ones fulfilling in addition the criterion on the ratio of volume densities.