High-latitude plasma outflow as measured by the DMSP spacecraft

We have examined the vertical ion flux in the topside high‐latitude ionosphere from measurements of the vertical ion drift and ion number density made by the DMSP F13 satellite. We found that the average vertical flux over the entire high‐latitude region near 800 km altitude is quite small. This suggests that most of the vertical ion flux is associated with a large‐scale “breathing” of the upper ionosphere. In the polar cap the vertical ion flux is uniformly downward at all locations. However, in the auroral zone the ion flux is highly structured, and a net upward flux is produced only by spatially and temporally confined events containing upward fluxes in excess of 1010 cm−2 s−1 that have no downward counterparts.