We have examined characteristics of the vertical O+ flux in the topside high-latitude ionosphere from measurements of the vertical ion drift and ion number density made by the Defense Meteorological Satellite Program (DMSP) F13 spacecraft from June 1996 to January 1997, June 1998 to January 1999, and June 2001 to January 2002. In the polar cap the vertical ion flux is, on average, downward at all locations. However, in the auroral zone the ion flux is highly structured, and a net upward flux is produced primarily by spatially and temporally confined events containing upward fluxes in excess of 109 cm-2s-1. These dominant high-flux events tend to be produced more commonly by high densities rather than by high velocities. The range of vertical velocity and number density changes with season and solar cycle with greater variability in the vertical velocity occurring during winter and at lower levels of solar activity. There is also evidence that the vertical fluxes are a function of the interplanetary magnetic field, with upward fluxes in the auroral zones for negative Bz and upward fluxes in the polar cap for positive Bz.