She later confirmed she wasn't imagining things by watching a video of that night's aurora activity taken at Poker Flat Research Range north of Fairbanks. Kimball and her advisor, Geophysical Institute Professor Emeritis Tom Hallinan, showed me a black aurora that was captured by a narrow-field camera at the former Ester Dome observatory in Fairbanks in the 1970s.
Black aurora occurs almost directly overhead in Alaska during diffuse auroras.
Diffuse auroras are nondescript displays about as bright as the Milky Way, according to Neil Davis in his book, The Aurora Watcher's Handbook. For her master's thesis work, Kimball observed dozens of examples of black aurora and came up with some fresh conclusions. When the aurora draws us outside with impressive displays, we're watching the interaction between particles from the sun and gases in Earth's atmosphere. These gases produce the color in auroras. The familiar whitish-green color of the aurora, for example, results when electron particles from the sun strike nitrogen molecules.