According to NASA, the process mirrors auroras but operates on routine sunlight. Daytime UV rays energize oxygen, nitrogen, and other molecules in the mesosphere and thermosphere. Come nightfall, they de-excite, releasing light photons in a process akin to a cosmic light show powered by the sun’s daily rhythm. Ionized particles occasionally colliding with free electrons add extra sparks to the display.

Why does the night sky never go fully dark? Strip away light pollution, lunar glow, and starlight, and airglow remains, accounting for about 10% of stellar illumination. From orbit, it forms a glowing halo around Earth, concentrated in the ionosphere between 50 and 400 miles high—the realm of satellite orbits and radio wave propagation.

Color coding reveals chemistry: dominant green from oxygen at 100 km altitude, reds from nitrogen-oxygen interactions higher up, and subtle hues from lesser-known reactions. The sparse air allows prolonged excitation, fostering brighter emissions than in collision-heavy lower atmosphere. Variations track diurnal solar input and meteorological influences, creating ever-shifting patterns.

Airglow serves as an atmospheric diagnostic tool, much like smoke trails map wind flows. It maps ionospheric flows, thermal profiles, and compositions, linking solar influences to Earth-bound weather. This intel is vital for forecasting space weather events that could scramble GPS or endanger astronauts.

ISS cameras routinely document these luminous layers, fueling studies that connect celestial forces with our planet’s climate. As climate change alters atmospheric dynamics, airglow research grows ever more crucial for global forecasting and space safety.