There is a growing body of evidence that energetic heavy ions observed at one or more Earth radii over the polar cap originate from the dayside ionosphere in the vicinity of the dayside cleft. The ions, consisting mostly of O+, are often characterized by conic pitch-angle distributions, suggesting that they have undergone acceleration transverse to geomagnetic field lines. This process of ion injection from a latitudinally localized source region in the dayside auroral oval followed by dispersal throughout the entire polar cap has been called the ''cleft ion fountain. But, except for placement of the ion injection source somewhere in the vicinity of the dayside auroral oval, very little is known about the altitude regime in which the source operates and the nature of the process that transports ionospheric ions into the magnetosphere. Results are presented of upward thermal-ion flows measured at 800-km altitude in the dayside polar ionosphere by the Hilat satellite. The characteristics of these thermal-ion upwellings (TIU) are described and shown to be closely associated with the cleft ion fountain. We show that TIU events are latitudinally confined and spatially collocated with cleft electron precipitation, upward field-aligned currents, and velocity gradients in magnetospheric convection. ¿ American Geophysical Union 1989