When the Fall Precedes the Rise: Lessons from the Temporal Evolution of Artificial Aurora Optical Emissions

The atomic oxygen red line emission is an important observable in ionospheric heating experiments. We report an analysis of extant observations of this emission that incorporates updated inputs on O(
¹
D) production as well as collisional relaxation by molecular nitrogen, molecular oxygen, and atomic oxygen. The results highlight the crucial role of O atoms in controlling the intensity and temporal evolution of artificial aurora optical emissions and provide an improved interpretation of the O(
¹
D) emission’s temporal evolution. This is especially relevant for altitudes below 250 km, where discrepancies between observed and calculated effective lifetimes have persisted. The O(
¹
D) emission decay lifetime is controlled by the competition between the rates of its production and collisional relaxation.