In-situ observations of a moderately strong midlatitude sporadic-E layer show a separation in altitude between distinct sublayers composed of Fe+, Mg+, and NO+. From these observations it is possible to estimate the zonal wind field consistent with diffusive equilibrium near the altitude of the layer. The amplitude of the zonal wind necessary to sustain the layer against diffusive effects is less than 10 m/s, and the vertical wavelength is less than 10 km. ¿ 2000 American Geophysical Union