Plasma on parade: Vast red sprites haunt the sky

They tower high in the sky, like huge jellyfish with extended tentacles. These red sprites appear above active thunderclouds and can grow up to 100km high. But they light up the sky for only a few milliseconds, so it has proven an almost impossible task to capture good photos of this mysterious phenomenon. The red sprites consist of ionised plasma, and they are triggered by powerful electric charges in the thunderclouds, from where the flashing light cascades downwards for those few milliseconds in an electrical avalanche.