Ansan-si What you’re seeing isn’t fireworks or a volcanic eruption—it’s a rare atmospheric phenomenon called a red sprite.

Sprites are massive electrical discharges that occur high above thunderstorm clouds, usually in the mesosphere (about 30–55 miles up). Unlike lightning bolts, which shoot down toward the ground, sprites leap upward toward space in branching, flame-like forms. Their red glow comes from excited nitrogen molecules in the upper atmosphere.

Because they’re faint, short-lived (a few milliseconds), and happen above storms rather than inside them, sprites weren’t photographed until 1989. They’ve since been nicknamed “jellyfish lightning” because of their umbrella or tendril-like shape.