AURORAL IONOSPHERIC ION FEEDING OF THE INNER PLASMA SHEET DURING SUBSTORMS

During the last decade, satellite observations in the nightside magnet osphere have confirmed the presence of energetic (>20 keV) ionospheric -origin ions in the near-Earth magnetotail. Observations also imply th at the feeding of the equatorial magnetosphere with ions from the high -latitude ionosphere can be very fast and intense at times. In the pre sent paper we use observations from the Combined Release and Radiation Effects Satellite (CRRES) to investigate the characteristics of ion e nergy density variations. :Multispecies studies of the energy density give important clues on the coupling of the different plasma sources a nd their participation in the substorm energization. The measurements, coming from the Magnetospheric Ion Composition Spectrometer (MICS), c onfirm previous results obtained from the AMPTE/CCE-CHEM spectrometer, with regard to the timing of the high-latitude ionosphere response to the equatorial magnetosphere disturbances. The energy density profile of the ionospheric-origin O+ follows the intensity enhancements of th e westward electrojet very closely in time, exhibiting a continuing in crease, contrary to the behaviour of the other major ion species H+ an d He++. This feature, which is consistent with statistical studies of AMPTE/CCE observations, points towards a fast activation of an extract ion/acceleration mechanism which feeds the inner plasma sheet with ion s of ionospheric origin during the substorm expansion.