Velocities of ions and various grains relative to the amplitude of the neutral velocity for n₀ = 10⁶ cm⁻³. The pink points correspond to the ion velocities, the dark points to the smallest grains, namely, of size a_min whereas the red points correspond to grain of size a_max. The blue, cyan, and purple points correspond to grain of intermediate sizes evenly distributed (logarithmically) between a_min and a_max.