SCIFER - STRUCTURE OF THE CLEFT ION FOUNTAIN AT 1400-KM ALTITUDE

The SCIFER, sounding rocket intersected the cleft ion fountain (CIF) a t an altitude of about 1400 km revealing the structure of upward flows and ion acceleration. This altitude range is intermediate, between lo wer altitude studies using DE-2 and HILAT data and higher altitude stu dies using DE-1 and EXOS-D data. Within the observed intense ion heati ng region the ions are consistent with satellite measurements of the c left ion fountain of DE-1, or the ''ion wall'' of EXOS-D obtained at m uch higher altitudes. We conclude from the SCIFER data set that the ac celerated ion flux levels at 1400 km altitude are similar to the TAI f luxes measured at higher altitudes. Furthermore the transversely accel erated ions are found within separate ''events'' of 30-40 km latitudin al width and have well-defined boundaries. The ion distribution functi on within an event indicates transverse-beating up to about 40 eV, occ urring a few tens of km below the rocket. The SCIFER data set serves t o demonstrate that the cleft ion fountain is composed of discrete stru ctures originating poleward of the electron trapping boundary in regio ns of depleted ionospheric density.