Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra. We present the electron energy and flux measurements from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of now three operating satellites observes the auroral zone in the UV from which electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate ionization rates and electron densities in the upper mesosphere and lower thermosphere (≈ 80–200 km). We present our validation study of the SSUSI-derived electron densities to those measured by the ground-based EISCAT radar stations. We find that with the current standard parametrizations, the SSUSI-derived auroral electron densities (90–150 km) agree well with EISCAT measurements, with differences between +/- 20% for F18, and +/- 50 % for F17. The largest differences are at the lower end of the altitude range because there the electron densities decline very rapidly.

Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. For example particle-produced OH and NO molecules affect the ozone content in the middle atmosphere. Climate models usually parametrize this ionization and the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra. We present electron energy and flux measurements from the Special Sensor Ultraviolet Spectrographic Imagers (SSUSI) satellite instruments. This formation of satellites observes the auroral zone in the UV from which electron energies and fluxes are inferred. We use these observed electron energies and fluxes to calculate ionization rates and electron densities in the mesosphere and lower thermosphere (≈ 40–200 km). We also present an initial comparison of these rates to other models and compare the electron densities to those measured by the EISCAT radar. Together with photochemical models, trace gas concentrations, for example of NO, can be calculated from these electron densities. These concentrations then provide an independent source for comparing and validating satellite trace gas measurements.