Red and Green Ripples in the Sky

May 15, 2020: This week, an astronomer at the McDonald Observatory discovered a planet with fantastic red and green ripples in its atmosphere. It looks a lot like Texas.

On May 13th, around 10:30 pm, Stephen Hummel was walking across the observatory grounds when he noticed the flash of lightning from a distant thunderstorm. “I saw a large column of sprites and rushed to set up my camera on a ridge with a better view,” he says. “Aiming southeast towards the city of Alpine, Texas, I recorded this movie.”

Hummel’s movie is rare and beautiful. It shows alternating bands of red and green airglow gliding overhead like ripples in a giant pool of water, punctuated by red bolts of upward directed lightning. The flickering sprites were so bright, he could see them with his unaided eye.

“In a hurry not to miss any action, I hiked quickly up the ridge with my camera,” he recalls. “Out of breath, I heard the eerie but distinct sound of a mountain lion’s call. I left the camera running while I returned to the safety indoors, then gathered the footage later on, hoping for the best. I was amazed by the results and surprised the airglow was so evident.”

Both the sprites and the airglow-ripples came from a thunderstorm about 180 miles away. This weather radar map shows Hummel’s location (starred) and the instigating storm system:

radarmap

This was a convective storm with powerful updrafts. Essentially, the storm pounded the upper atmosphere from below, creating a bulls-eye pattern in the mesosphere more than 80 km above the ground. This pattern impressed itself upon the airglow layer, exciting and amplifying aurora-like colors which are usually too faint to see.

It’s no coincidence that Hummel saw sprites at the same time. Powerful convective storms produce strong lightning–both up and down. Hummel witnessed not only the bright glow of ordinary lightning bolts lancing down to Earth, but also the eerie forms of sprites reaching up to the edge of space. “The sprites were easily visible to the unaided eye,” he says.

“Thanks to the mountain lion,” he adds, “I recorded the whole thing.”

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