TAILWARD ENERGETIC ION STREAMS OBSERVED AT SIMILAR-TO-100 R(E) BY GEOTAIL EPIC ASSOCIATED WITH GEOMAGNETIC-ACTIVITY INTENSIFICATION

We report energetic particle (EPIC instrument) and magnetic field (MGF instrument) measurements collected onboard GEOTAIL located at similar to 100 R(E) downstream in the magnetotail during a 13-hour long activ e period on January 20-21, 1993. During this period, a series of 6 geo magnetic activity intensifications (breakup or pseudo-breakup) have be en studied with ground magnetograms and energetic particle data at geo synchronous orbit. We show that: (1) as a general trend, the level of the energetic ion fluxes was related to the intensity of the westward electrojet; (2) a systematic temporal (within a few minutes) correlati on exists between energetic ion flux enhancements observed by GEOTAIL/ EPIC in the distant tail and neat-Earth geomagnetic activity intensifi cation onsets; and (3) for 5 of 6 cases, these energetic ion flux enha ncements corresponded to strong tailward streams which included partic les of both solar wind and ionospheric origin. Their amplitude seemed also to be related to the electrojet intensity change.