Abstract
Quasi pulsive depleting plasma density variations with period ranging from a few to a few tens sec with depletion up to 30 to 50% of the ambient non-depleted plasmapause density have been observed in the occasion of the plasmapause crossing by the Akebono (EXOS-D) satellite, in association with the enhancements of the local upper hybrid mode plasma waves. The phenomena are strictly related to the magnetospheric substorm phenomena with enhancements of normal kilometric radiations (AKR) which are emitted from the auroral region. These evidences are concluded to be caused by quasi-pulsive energy injections into the plasmapause region from the plasma sheet, possibly in the form of fast plasma streams, relating to substorms and magnetospheric disturbances. As for the origin of the simultaneous energy injection into the auroral and sub-auroral regions, the induced electric field by the disruption and/or the rapid change of the current sheet in the inner plasma sheet are discussed. The induced electric field should enhance the fast plasma injection from the inner magnetosphere to the plasmapause region due to the E x B drift, and also the field should be transported down to the amoral region along magnetic fields making a concentrated particle acceleration region which cause the enhancement of AKR.
