Ion density and vertical ion drift velocity sampled at 1024 Hz from the ROCSAT 1 satellite are used to examine the behavior of horizontal structures in equatorial spread F near 600 km altitude. An initial investigation shows that at scale sizes less than 100 m the relationships between the vertical drift and density structure are distinguished by the bulk plasma flow in the structure and by the background gradient in the density. Two adjacent equatorial bubble structures are examined: one in which the bulk plasma flow is upward and characteristic of an active evolving bubble and the other in which the bulk plasma flow is small and characteristic of a stagnated structure. We find that at scale sizes less than 100 m the velocity structure has a spectral slope that is consistently shallower than that of the density structure in the stagnated bubble but matches closely the spectrum of the density structure in the active bubble. Each of the bubble regions examined are characterized by one edge that has a much larger background gradient than the other. We find that in these bubbles, observed near 600-km altitude, the lower background gradient is characterized by enhanced structure at 1-km scale sizes. ¿ 2001 American Geophysical Union