dark lightning

They’d found the source of the dark lightning.

After dark, lightning flashed, not so much from cloud to ground as within clouds, illuminating their inner shape and structure.

Three sea lions streaked like dark lightning bolts underwater, then leapt onto a pile of boulders or the edge of the pool.

These bursts produce very little visible light, inspiring Joseph Dwyer to dub them "dark lightning".

But he also notes that recent data from an Italian satellite implies that thunderstorms might be producing gamma-ray flashes far more energetic than Dwyer’s theory can account for, adding mystery even as it helps confirm dark lightning’s existence.