As in Fig. 8, but using the method to estimate the likelihood of clumping instead of the KS-derived method. The figure marks the region of the particle size vs. concentration phase space where the streaming instability is active. Particle size is measured in the stopping time τ_f and the particle concentration is Z = Σ_solid/ Σ_total. The colors mark the probability that particle clumps can form, where red is “unlikely”, magenta is “somewhat likely”, blue is “likely”, and green is “very likely”. When different simulations give different results, the two extreme values are shown. The symbols indicate the number of simulations available. The circle, cross and triangle indicate, respectively, one, two and three simulations. Regions without symbols are extrapolations. To facilitate the comparison with Fig. 8, the boundary marked by the black lines has been copied from Fig. 8 without modification.