Fig. 1.
Grain velocities v as a function of grain radius a. Two grain species, (a) silicate and (b) carbonaceous dust, are shown. The solid lines indicate the velocity calculated by Yan et al. (2004) with the physical condition of the WIM described in the text. The dashed line shows the simplified velocity model (Eq. (10)) with ac = 10−6 cm. The dotted line shows the shattering threshold velocity.