Little-known phenomenon gives the California sky an unusual red glow

The northern lights, or aurora borealis, usually light up skies over the most remote parts of the world such as Iceland and Alaska, but on Sunday night during a geomagnetic storm they appeared farther south than usual, including northern latitudes of the United States and Europe.

While there were no reports of the aurora borealis in California, another type of natural light display that can also occur during these storms was captured with a camera. 

A Stable Auroral Red, or SAR, arc appears as a shimmery red curtain of light spread across the sky, usually at lower latitudes than the aurora borealis. It’s usually invisible to the human eye but can be detected by special equipment that’s part of most modern-day cameras, including iPhones. Photographer Dakota Snider captured the phenomenon with his camera on Sunday night near his home in Mammoth Lakes, Calif. — and he was wowed.

“Maybe an hour after sunset, I took a photo and you could see the red glow appearing in the distance,” Snider said. “I was screaming and running around and my friends were laughing. And I was so excited because I knew as it continued to get darker it was only going to get better. I knew we were in for a treat.”

SAR arcs were first discovered in 1956. Bryan Brasher, a project manager with NOAA’s Space Weather Prediction Center, said the agency does not closely track SAR arcs because they do not impact technology systems like the better known northern and southern lights can. 

A SAR arc was also captured on the East Coast in Virginia’s Shenandoah National Park, which sits at a similar latitude to Mammoth Lakes. Snider said he tracked reports of the aurora borealis on social media on Sunday and when he saw a report of the SAR ark in Shenandoah, he thought one could occur in the Mammoth Lakes area, where he lives. Since the East Coast was a few hours ahead, Snider had time to get his equipment and some friends together and find the right location to take photographs.

“We didn’t have completely clear skies in some places, so we drove north to the Mono Lake Basin area,” he said. “Right after sunset, you could start to see the red signature appear on the camera.” 

The northern lights put on a spectacular display in locations around the world on Sunday night during a strong geomagnetic storm, level 3 out of 5 on NOAA’s scale. Scientists understand why the northern lights occur during these geomagnetic storms: The sun expels plasma, or charged particles, that collide into the Earth’s atmosphere, interacting with atoms and molecules and emitting lights of all color. SAR arcs occur under different circumstances. The red glow comes from heat energy released from what’s known as the Earth’s ring current system, a flow of electrons located in the magnetosphere and drifting around the Earth, Jeff Baumgardner of Boston University’s Center for Space Physics told SFGATE.

“That region has field lines that come down into the Earth’s atmosphere and guide the heat energy and heats up the oxygen atoms in the atmosphere — that’s where the light is coming from,” Baumgardner said. “The field lines are always there but that region with the ring current is being heated up and energized during a geomagnetic storm. On Sunday night, that ring current was pumped up with energy.”

As a result of all of this, social media exploded with images of SAR arcs, and among those was Snider’s photo.

“What a night,” he captioned the photo on Instagram.