But there's more to the story. Only a fraction of the lights he saw were actual auroras. Note the red arc at the top of his photo. That's something else--an "SAR."
SARs are red arcs of light that ripple across the sky during some geomagnetic storms. They 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 SARs.
In fact, SARs are neither stable nor auroras. Auroras appear when charged particles rain down from space, hitting the atmosphere and causing it to glow like the picture tube of an old color TV. SARs form differently. They are a sign of heat energy leaking into the upper atmosphere from Earth’s ring current system--a donut-shaped circuit of plasma carrying millions of amps around our planet.
"Seeing auroras from China is very difficult," says Dai. "It happens maybe 1-2 times every 11 years." Seeing an SAR is even more rare. It was a dreamy night, indeed.