Fig. 1. The maximum particle density versus time for streaming instability simulations without self-gravity at resolutions 64³ (black line), 128³ (yellow line), and 256³ (blue line).

Particle density is measured in units of the mid-plane gas density ρ_g and time in units of the orbital period T_orb. The first 30 orbits are run with a solids-to-gas ratio of Z = 0.01, with only modest overdensities seen in the particle density. Half of the gas is then removed over the next 10 orbits, triggering strong particle concentration, of up to 10,000 times the local gas density at the highest resolution. Doubling the resolution leads to a more than a quadrupling of the maximum particle density.