Aurora Borealis
Definition
The Northern Lights — glowing light in the northern night sky produced when solar particles make the upper atmosphere emit light.
In plain language
When charged particles from the Sun reach Earth, our magnetic field steers them toward the north polar region, where they crash into air molecules and make the sky glow in green, red, and purple curtains.
The science
Precipitating electrons, accelerated within the magnetosphere, collide with atomic oxygen and molecular nitrogen between roughly 80 and 600 km altitude. Collisional excitation followed by radiative de-excitation produces discrete emission lines, dominated by the 557.7 nm oxygen green line. The name combines Aurora (Roman dawn goddess) and Boreas (Greek north wind).
Why it matters for aurora viewing
It is the show itself — everything else in this glossary exists to help you predict when and where the borealis will appear.
See this in action on tonight's data.