SPRITE is a simple acronym that describes a complicated phenomenon. It stands for Stratospheric Perturbations Resulting from Intense Thunderstorm Electrification. It is a rare kind of lightning that occurs high above thunderstorm clouds.
Sprites are massive discharges of electricity in the Earth’s upper atmosphere. They often take the form of bright red, jellyfish-like lightning. Sprites are also known as cloud-to-space lightning.
One of the first sprite lightning images. Photo: University of Alaska Fairbanks
Transient luminous events
Sprite lightning is a Transient Luminous Event (TLE). TLEs are a group of upper atmospheric luminous phenomena that occur only at very high altitudes. They are mostly associated with thunderstorms and cumulonimbus clouds.
Other TLEs include ELVES (Emission of Light and Very Low-Frequency Perturbations from Electromagnetic Pulse Sources), Blue, Secondary and Gigantic Jets, as well as Halos. These types of TLEs appear as huge columns of light shooting out from thick cumulonimbus clouds, or as large glowing rings hovering ominously in the atmosphere.
People have sighted Sprites since the 1800s, but scientists had no evidence of their existence until the late 1980s. In 1989, two physicists took the first photograph of a Sprite by accident. The pair, from the University of Minnesota, was testing low-light television cameras on a stormy night. Thunderstorms from Hurricane Hugo were raging nearby and the pair managed to capture the Sprite above a thundercloud. Over the years, more images have popped up, from NASA, planes, and weather services. People have seen Sprites worldwide.
Red Sprite above a thunderstorm. Photo: John D. Sirlin/Shutterstock
Positively charged lightning
Sprites occur when there is a change in the electric field between negative charges at the top of thunderstorms and positive ions in the ionosphere. The Sprite is positively charged lightning, a type that makes up only 5% of lightning strikes.
If you do manage to snap a photo of a Sprite, you will see how different it is from regular lightning. While lightning bolts are usually three to four kilometres long, Sprites come in clusters and can reach up to 50km. They form at altitudes of up to 90km and they last from 5 to 300 milliseconds.
You can see them with the naked eye but you must be somewhere dark, with little or no light pollution, and a clear view of a storm. If you’re really lucky, you might be able to capture them with accompanying ELVES, Halos, and Ghosts (small green afterglows).
Gigantic jet, a cousin of the sprite, taken in Hawaii. Photo: International Gemini Observatory/NOIRLab/NSF/AURA/A. Smith
Sprites come in three subcategories: jellyfish, column, and carrot (physical characteristics whose names are self-explanatory). They are mostly red, but their ‘tentacles’ transition into blue. Like most luminous phenomena, the dominant element present determines the color. Nitrogen makes red and blues, which is the dominant element at the altitudes that Sprites form.
As mesmerizing as Sprites are, they are not completely benign. NASA believes that sprites were somewhat responsible for damage done to one of their balloons traveling to the stratosphere. A study done by the Florida Institute of Technology stated that they are also capable of disrupting long-range communications.
