The position of 20,000 released particles from the surface source region, with positions along their trajectory selected randomly in time between 0 and 600 s. The particles are released in random orientations and from random positions in their source region between −8 km < X < 8 km, and at random velocities centered at 380 m s⁻¹ having a Gaussian spread of +/−95 km s⁻¹. For the instantaneous time considered, about one-half of the released particles have landed onto the surface.