Transient Luminous Events: Sprites, Jets and Elves Are Mysteries in the Sky (PHOTOS)

By: Chrissy Warrilow

Published: August 19,2013

 

 

 

Carrot sprites visible in strong moonlight, May 26, 2013. (Courtesy Thomas Ashcraft)

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High above the tops of active thunderstorms, often while lightning flashes towards the ground, red flames, blue streaks or sometimes circular doughnuts flash upward toward the sky. These visual phenomena are called transient luminous events (TLEs).
They can happen in the blink of an eye and are extremely rare forms of upper-atmospheric electromagnetism. If you're lucky – or extremely patient– you may witness these astro-meteorological pixies in the sky. Each day lightning strikes the Earth 8.6 million times, on average, dramatically illustrating the extreme buildup of static electricity in the sky. However, cloud-to-ground lightning is only half of the picture.

Sprites, Jets and Elves

Transient luminous events can be broken down into sprites, jets and elves.

Transient Luminous Events

This chart illustrates the different transient luminous events (TLEs) that occur in the atmosphere. (Courtesy of NOAA. Adapted from Carlos Miralles, AeroVironment, and Tom Nelson, FMA.)

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Red sprites appear high in the atmosphere, usually 25 to 55 miles above thunderstorms, with tendril-like structures that extend downward as far as 25 miles. They usually are associated with positively charged cloud-to-ground lightning strikes.
Atmospheric researchers have discovered that sprites are common above the decaying portion of large mesoscale convective systems but are rare above supercell thunderstorms.
Sprites are thought to occur due to ionization of the upper atmosphere above terrestrial lightning strikes. When a positively charged lightning bolt strikes the ground, it leaves the top of the thunderstorm negatively charged. When enough electric potential builds up, a discharge results in the form of a red sprite.
It is possible to see red sprites with the naked eye, but special video and photography equipment, coupled with elevated observation stations, increase the likelihood of observing the beautiful scarlet flashes.
Blue jets are a visual phenomenon that propel upward from active thunderstorms. They can extend up to 12 miles from the top of the thundercloud, though they are not necessarily associated with a specific cloud-to-ground lightning strike. Atmospheric research indicates that blue jets only last one-tenth of a second, making them difficult to see with the naked eye. Scientists are still unsure as to what causes blue jets and how they form.
Elves are electromagnetic pulses generated by lightning strikes. Elves is an acronym for Emission of Light and Very Low Frequency Perturbations Due to Electromagnetic Pulse Sources. They look like doughnut-shaped flashes that spread laterally up to 186 miles. Atmospheric research indicates the brightness of elves is closely related to the peak current in a return lightning stroke (the movement of charges from the ground to the cloud), and that elves may be the most dominant type of TLEs in the atmosphere.
New transient luminous events are discovered every year, and a full list of the ethereal phantoms are available from the University of Albany-SUNY.

How to Catch an Enigma

Interested in capturing your own sprites, jets and elves? Thomas Ashcraft, whose photo gallery is featured above, shares his technique on his website Heliotown.com.
"At the moment I have two separate video observing systems and I recently acquired a modified Canon XS DSLR camera with the infrared filter removed and replaced with a clear full spectrum filter which has good sensitivity in the 600 nm to 900 nm wavelength range where sprites are most visible. On July 31, 2011, I was able to capture three separate sprite clusters above a storm near Clovis, New Mexico about one hundred miles away."