VLF PLASMASPHERIC EMISSIONS - WAVE SIGNATURES OF INNER MAGNETOSPHERE BOUNDARIES

VLF quarter-gyrofrequency emissions have been observed in the plasmasp here by low-altitude (up to 2500 km) Intercosmos satellites. Their exp erimental characteristics indicate that the origin and the distributio n function of resonant electrons and the type of instability leading t o their production can differ during various phases of magnetospheric disturbances. Their close connection to the earthward edge of the lowe st energy plasma sheet electron fluxes during active periods is shown. During recovery periods following magnetospheric substorms, they pers ist (together with other symptoms of a certain internal plasmaspheric structure-subauroral T(e)-peaks, SAR arcs, etc.) at roughly the same L -value within the new, more distant plasmapause. A new kind of instabi lity is mentioned which could lead to their production during the reco very phase of magnetospheric substorms.