Red sprites

A red sprite is a transient luminous event (TLE): a short-lived optical emission above an active thunderstorm. NASA places sprites at roughly 80 kilometres altitude, far above the storm clouds. Photographs show a range of forms, including diffuse plumes and branching, spiny tendrils; groups may appear to switch on and off in rapid succession. The familiar red colour and varied shapes have inspired the name, but sprites are physical atmospheric electrical phenomena, not ordinary cloud-to-ground lightning travelling upward.

Sprites are linked to electrical activity in their parent storms. Research observations associate many sprites with strong positive cloud-to-ground lightning strokes, which can alter the electric field above a storm. The details of initiation and the conditions that determine sprite shape remain research questions. A review of proposed mechanisms discusses electrical breakdown of air, including streamer-like processes and runaway-electron models; the existence of competing explanations reflects continuing work rather than a single settled account of every sprite.

Sprites belong to a broader family of transient luminous events observed above thunderstorms. Other named types include elves, blue jets and gigantic jets, which differ in appearance and in where or how the luminous activity develops. A 2022 observation over South Asia documented 105 red sprites in association with one thunderstorm, along with 16 secondary jets and at least four green emissions called ghosts. These terms describe distinct observed patterns; they should not be treated as interchangeable names for sprites.

Sprites last only briefly and are usually difficult to see from the ground, so low-light photography and carefully timed observations are important. The first credible camera evidence was recorded accidentally in 1989 by University of Minnesota researchers testing a low-light television camera. Modern research combines photographs and video with lightning and satellite data to connect flashes to storms. NASA’s Spritacular citizen-science project gathers public observations, helping researchers build a more accessible image record of sprites and other TLEs.

Because sprites occur above thunderstorms, they provide a way to investigate electrical coupling between storms and the upper atmosphere. They are also relevant to questions about atmospheric conductivity, energy transfer and chemistry. Their sparse and opportunistic observations limit estimates of how often they occur and how their characteristics vary. Crowdsourced image collections, when paired with reliable timing and location information and checked by researchers, can strengthen the evidence base, but a photograph alone may not establish the event’s physical cause.