But three records noted phenomena that were likely candidates for auroras: "red glow," "red cloud" and "red sky," according to the study.

"These descriptions themselves are quite consistent with the early modern descriptions of auroral display," Hayakawa told Live Science in an email. Indeed, red is a color typically found in low-altitude auroras and in auroras produced by low-energy electrons, the researchers reported.

A typical aurora — sometimes called the northern lights or the southern lights, depending on the hemisphere in which it's located — occurs when charged particles from the sun interact with Earth's oxygen and nitrogen molecules. This interaction excites the molecules and causes them to glow.

But STEVE, formally known as Strong Thermal Emission Velocity Enhancement, is different. In the Northern Hemisphere, the phenomenon is visible from areas farther south than a typical aurora, and it looks like a ribbon of pink or mauve light. Sometimes, STEVE even has a "picket fence" appearance, with green columns of light passing through the ribbon. Auroras, by contrast, usually are shimmering green ribbons.

Now, new research on the phenomenon suggests that the picket-fence aspect of STEVE is caused by a similar mechanism as the process that results in an aurora. STEVE's mauve streaks occur when charged particles are heated up high in the atmosphere, further south than typical auroras. "This occurs outside the auroral zone, so it's indeed unique," Bea Gallardo-Lacourt, a space physicist at the University of Calgary in Alberta, Canada, and co-author of the new research, said in a statement released by the American Geophysical Union, which published the new research.
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When STEVE was on display, the study authors realized, energetic electrons were pouring into Earth's ionosphere, the layer of the planet's atmosphere where atoms lose electrons due to solar and cosmic radiation. The friction that flood creates heats particles, which creates the pinkish glow, almost like an incandescent light bulb.

https://www.space.com/steve-aurora-powered-by-electrons.html