Departures from. diffusive eq~~briu ~ in the topside F-layer from satellite soundings

Abstract-A method for the detection of O+ ion fluxes from topside soundings is described. The shape of the plasma scale-height profile is altered by such flows only at heights near the F2-peak, where ion-neutral drag is large. Model profiles are used to relate changes in scale height to the ratio (4/&) where 4 is the field-aligned 0 ’ flux (relative to the neutral air) and cPt is the limiting value set by frictional drag. Values of(+/&L) can then be determined to within a few per cent from experimental soundings, using the plasma temperature and its gradient {as deduced from the observed profile) and the MSIS model neutral tem~rature. It was found that 3700 topside profiles show departures from diffusive equilibrium, out of 10,oaO used to obtain the global morphology of (&/4,j near the sunspot minimum. Results reveal dynamic ion-flow effects such as the transequatorial breeze and the effects of the polar wind and protonospheric replenishment light-ion flows can be infeired. 1