According to
Spaceweather.com :
SAR arcs were discovered in 1956 at the beginning of the Space Age. Researchers didn't know what they were and unwittingly gave them a misleading name: "Stable Auroral Red arcs" or SAR arcs. In fact, SAR arcs are neither stable nor auroras.
Auroras appear when charged particles rain down from space, hitting the atmosphere and causing it to glow. SAR arcs form differently. They are a sign of heat energy leaking into the upper atmosphere from Earth's ring current system–a donut-shaped circuit carrying millions of amps around our planet.
"On Nov. 5th, the ring current was pumped up by hours of strong geomagnetic storming, with energy dissipating into these SAR arcs," says Jeff Baumgardner of Boston University's Center for Space Physics. "It was a global event. Our cameras registered SAR arc activity from Italy to New Zealand."
A magnificent photograph from New Zealand was published on APOD a few days ago:
https://apod.nasa.gov/apod/ap240103.htmlThis SAR was observed a few minutes after an
Aurora Borealis over France It lasted at least an hour or two.
Technical data: Sony A7S Astrodon on a simple tripod, Samyang 14mm f2.8, 15s, 2000 ISO. Processed with DxO PhotoLab.
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