Rocket observations of precipitating electrons over a pulsating aurora

Data from the third rocket of the Substorm‐GEOS series have been studied. The rocket was launched from ESRANGE on January 27, 1979 at 21.52.20 UT into a pulsating aurora. Measurements were performed in the energy range 0‐33 keV with electrostatic analyzers and above 48 keV with solid state detectors. The pulsations are visible in the data above 3‐4 keV. In a pulsation maximum the bulk of the energy flux is carried by electrons of energies between 5 and 40 keV. In pulsation minima the bulk of the energy flux is carried by particles of lower energies. In the electron fluxes above 25 keV a modulation of about 3 Hz is seen in the loss cone. This modulation is seen only in pulsation maxima and the modulation depth increases with increasing energy.