Interpretation of electron spectra in morningside pulsating aurorae

Abstract

Energy spectra of precipitating electrons in morningside aurorae were obtained with instruments on the NOAA 6 satellite during several passes through the southern auroral zone in 1982. It is substantiated with the aid of coordinated data from particle detectors and a photometer in the Simulated Emission of Energetic Particles experiment payload on satellite S81‐1 that the precipitation observed by NOAA 6 was probably in a region of pulsating aurorae. The particle detectors and forward/downward looking quadrant photometer onboard S81‐1 all exhibited regular modulations at a period of about 5–15 s. The particle detectors on NOAA 6 showed fluctuating electron intensities over an energy range from several kiloelectronvolts to many tens of kiloelectronvolts, superimposed on a steady background component extending down to energies less than 1 keV. The NOAA 6 electron observations are in qualitative agreement with a time‐dependent precipitation model that includes the production of backscattered and secondary electrons from the atmosphere. In this model the time variations imposed on the precipitation are restricted to the energetic portion of the electron spectrum, while the integrating effects inherent in the production of backscattered and secondary electrons, together with phase mixing introduced as those electrons transit between conjugate hemispheres, insure the existence of a nearly time independent population of low‐energy electrons. A steady background precipitation is thereby created as a natural consequence of a time‐variable primary precipitation.