Particle Stokes numbers as a function of mass, in the midplane of an MMSN disk at 5 AU. Different lines show compact particles (red), porous aggregates with constant φ = 10⁴ (yellow), and aggregates with a constant fractal dimension of 2.5 (green). For the solid lines, all drag regimes (Epstein, Stokes and Newton) have been taken into account, while the dashed lines indicate the results using only Epstein and Stokes drag. Horizontal lines indicate Ωt_s = 1 (where drift is fastest) and Ωt_s = α = 10^-3 (where particles start to settle to the midplane).