Diurnal, seasonal, and nighttime variations of atomic nitrogen in the equatorial thermosphere

The open source neutral mass spectrometer on board the equatorial Atmosphere Explorer E satellite (AE‐E) measured atomic nitrogen densities at frequent intervals during both the elliptical and circular orbit phases of satellite operations. Elliptical orbit data presented here by means of empirical models at 225‐ and 300‐km altitude provide diurnal and seasonal profiles at altitudes lower than previously possible. Data from individual circular orbits later in the AE‐E mission confirm essential features of these models, particularly the diurnal density profile. At lower altitudes, considerable variation is evident near midnight, with density enhancements correlated with increasing levels of geomagnetic activity.