From the article:

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.