CHARGED-PARTICLE BEHAVIOR DURING THE ACTIVE PHASE OF THE APEX EXPERIMENT

The Active Plasma Experiment (APEX) uses intensive electron beam emiss ion for the study of dynamic processes in the magnetosphere and upper ionosphere. The beam energy and current is as high as 8 keV and 100 mA and the pitch angle of the emission varies in the range from 50 degre es to 80 degrees. The basic cycle of electron injection is formed by c urrent pulses of different duration, intensity and frequency. The spac ecraft potential is balanced by a low energy xenon plasma generator du ring the electron beam injection. The response of the environment is s tudied by the PEAS charged particle spectrometer working in the energy range 0.1-25 keV. The common response to the beam emission is the inc rease of the intensity of the registered electrons with energy less th an 2 keV. Under some circumstances (the satellite position, the inject or regime, the beam direction with respect to the magnetic field etc.) , strong electron fluxes of the order of 10(7) cm(-2)sec(-1)keV(-1) ha ve been observed. The energy of these fluxes is in general a rising fu nction of the mean current of the emitted beam bur never exceeds the b eam energy. The energy-angular distribution exhibits a complicated str ucture with the maximum energy located at the pitch angle which corres ponds to that of the emitted electron beam.