Thermal (0-25 eV) ion observations in the altitude range 5000 km to 10,000 km and at invariant latitudes greater than ~60¿,made by the Suprathermal Ion Mass Spectrometer (SMS) on the EXOS-D satellite, are used to estimate temperatures, densities, composition, and drift velocities of the local major thermal ion population during a 22-day period in February 1990. This preliminary study indicates that equatorward of a high-latitude boundary, higher-density cold ions corotate with Earth and field-aligned drift velocities are low (<1 km/s). These observations are consistent with a plasmaspheric origin for these ions; however, densities measured near the boundary (10-100cm-3) suggest that this boundary lies in or near the trough region. Poleward of this boundary, convection patterns deviate from corotation, and large upward directed field-aligned flows of iono-spheric plasma, consistent with a ''polar wind like'' source mechanism, are detected. Typically, parallel driftvelocities of 12, 7, and 3 km/s for H+, He+, and O+ are observed. Correlations of these plasma parameters, which were obtained approximately once per day, with magnetic activity (Kp) suggest response times of 2-3 days between the onset of Kp changes and the establishment of new, large-scale, steady state conditions. The implications of these results with regard to ionospheric plasma dynamics associated with depletion and replenishment of high-latitude flux tubes are discussed. ¿ American Geophysical Union 1992