Upper-atmospheric lightning and ionospheric lightning are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds. Upper-atmospheric lightning is believed to be electrically induced forms of luminous plasma. The preferred usage is transient luminous event ( TLE), because the various types of electrical-discharge phenomena in the upper atmosphere lack several characteristics of the more familiar tropospheric lightning.
Transient luminous events have also been observed in Ultraviolet images of Jupiter's upper atmosphere, high above the altitude of lightning-producing water clouds.
Characteristics
There are several types of TLEs, the most common being sprites. Sprites are flashes of bright red light that occur above
storm systems. C-sprites (short for "columniform sprites") is the name given to vertical columns of red light. C-sprites exhibiting tendrils are sometimes called "carrot sprites". Other types of TLEs include sprite halos, ghosts, blue jets, gigantic jets, pixies, gnomes, trolls, blue starters, sprelves and ELVESs. The acronym ELVES (“emission of light and very low frequency perturbations due to electromagnetic pulse sources”) refers to a singular event which is commonly thought of as being plural. TLEs are secondary phenomena that occur in the upper atmosphere in association with underlying
thunderstorm lightning.
TLEs generally last anywhere from less than a millisecond to more than 2 seconds. The first video recording of a TLE was captured unexpectedly on July 6, 1989, when researcher R.C. Franz left a camera running overnight to view the night sky.
TLEs have been captured by a variety of optical recording systems, with the total number of recent recorded events (early 2009) estimated at many tens-of-thousands. The global rate of TLE occurrence has been estimated from satellite (FORMOSAT-2) observations to be several million events per year.
History
In the 1920s, the Scottish physicist C.T.R. Wilson predicted that electrical breakdown should occur in the atmosphere high above large thunderstorms.
[C. T. R. Wilson (1924) "The electric field of a thundercloud and some of its effects," Proceedings of the Physical Society of London, 37 (1) : 32D-37D. Available on-line at: University of São Paulo .][Earle R. Williams (November 2001) "Sprites, elves, and glow discharge tubes," Physics Today, 54 (11) : 41–47. Available on-line at: Physics Today .] In ensuing decades, high altitude electrical discharges were reported by aircraft pilots and discounted by
until the first direct visual evidence was documented in 1989.
Several years later, the optical signatures of these events were named 'sprites' by researchers to avoid inadvertently implying physical properties that were, at the time, still unknown.
The terms
red sprites and
blue jets gained popularity after a video clip was circulated following an aircraft research campaign to study sprites in 1994.
Sprites
Sprites are large-scale electrical discharges which occur high above a
thunderstorm cloud, or
cumulonimbus, giving rise to a quite varied range of visual shapes. They are triggered by the discharges of positive lightning between the thundercloud and the ground.
The phenomena were named after the mischievous sprite, e.g., Shakespeare's Ariel or Puck,
[From page 128 of: John Friedman, Out of the Blue: A History of Lightning (New York, New York: Random House, Inc., 2008):]
"Dr. Davis Sentman of the University of Alaska, one of the few scientists studying these luminous, ghostlike phenomena i.e.,, named the eerie flashes of colored lights after Shakespeare's mischievous spirits of the air — Ariel in The Tempest and Puck in "A Midsummer Night's Dream." and is also a
backronym for stratospheric/mesospheric perturbations resulting from intense thunderstorm electrification.
They normally are colored reddish-orange or greenish-blue, with hanging tendrils below and arcing branches above. They can also be preceded by a reddish halo, known as a sprite halo. They often occur in clusters, reaching above the
Earth's surface. Sprites have been witnessed thousands of times.
[Walter A. Lyons and Michey D. Schmidt (2003). P1.39 The Discovery of Red Sprites as an Opportunity For Informal Science Education. American Meteorological Society. Retrieved on February 18, 2009.] Sprites have been held responsible for otherwise unexplained accidents involving high-altitude vehicular operations above thunderstorms.
Jets
Although jets are considered to be a type of upper-atmospheric lightning, it has been found that they are components of tropospheric lightning and a type of cloud-to-air discharge that initiates within a thunderstorm and travels upwards. In contrast, other types of TLEs are not electrically connected with tropospheric lightning—despite being triggered by it. The two main types of jets are
blue jets and
gigantic jets.
Blue starters are considered to be a weaker form of blue jets.
Blue jets
Blue jets emanate upwards from cloud tops at speeds of about and have a conical shape extending up to around in altitude, lasting 200 to 300 milliseconds.
They are also brighter than sprites and, as implied by their name, are blue in color. The color is believed to be due to a set of blue and near-
ultraviolet emission lines from neutral and ionized molecular
nitrogen. Blue jets are believed to be initiated as "normal" lightning discharges between the upper positive charge region in a thundercloud and a negative "screening layer" present above this charge region. The positive end of the leader network fills the negative charge region before the negative end fills the positive charge region, and the positive leader subsequently exits the cloud and propagates upward.
Blue jets are mainly generated by thunderstorms with high rates of negative cloud-to-ground lightning.
It was previously believed that blue jets were not directly related to lightning flashes, and that the presence of
hail somehow led to their occurrence.
[ Fractal Models of Blue Jets, Blue Starters Show Similarity, Differences to Red Sprites] They were first recorded on October 21, 1989, on a
monochrome video of a thunderstorm on the horizon taken from the
Space Shuttle as it passed over
Australia.
Blue jets occur much less frequently than sprites. By 2007, fewer than a hundred images had been obtained. The majority of these images, which include the first color imagery, are associated with a single thunderstorm. These were taken in a series of 1994 aircraft flights to study sprites.
['Red Sprites & Blue Jets – the video'[6], 'Blue Jets & Blue Starters – the video'[7].] More recently, the source and formation of blue jets has been observed from the International Space Station.
Blue starters
Blue starters were discovered on video from a night time research flight around thunderstorms
[Examples may be seen in the clip 'Blue Jets & Blue Starters – the video' [8].] and appear to be "an upward moving luminous phenomenon closely related to blue jets."
They appear to be shorter and brighter than blue jets, reaching altitudes of only up to 20 km.
[ Blue jets ] "Blue starters appear to be blue jets that never quite make it," according to Dr. Victor P. Pasko, associate professor of electrical engineering.
[ Fractal models of blue jets, blue starters show similarity, differences to red sprites]
Gigantic jets
Where blue jets are believed to initiate between the upper positive charge region and a negative screening layer directly above this region, gigantic jets appear to initiate as an intracloud flash between the middle negative and upper positive charge regions in the thundercloud. The negatively charged leader then escapes upward from the cloud toward the ionosphere before it can discharge within the cloud. Gigantic jets reach higher altitudes than blue jets, terminating at 90 km.
While they may appear to be visually similar to carrot-type sprites, gigantic jets differ in that they are not associated with cloud to ground lightning and propagate upward from the cloud at a slower rate.
Observations
On September 14, 2001, scientists at the Arecibo Observatory photographed a gigantic jet—double the height of those previously observed—reaching around into the atmosphere.
The jet was located above a thunderstorm over an ocean, and lasted under a second. The jet was initially observed to be traveling up at around at a speed similar to typical lightning, increased to , but then split in two and sped upward with speeds of at least to the
ionosphere where it then spread out in a bright burst of light.
On July 22, 2002, five gigantic jets between in length were observed over the South China Sea from Taiwan, reported in Nature.
On November 10, 2012, the Chinese Science Bulletin reported a gigantic jet event observed over a thunderstorm in mainland China on August 12, 2010. "GJ event that was clearly recorded in eastern China (storm center located at 35.6°N,119.8°E, near the Huanghai Sea)".
On February 2, 2014, the Oro Verde Observatory of Argentina reported ten or more gigantic jet events observed over a thunderstorm in Entre Ríos south. The storm center was located at 33°S, 60°W, near the city of Rosario.
On August 13, 2016, photographer Phebe Pan caught a clear wide-angle photo of a gigantic jet on a wide-angle lens while shooting Perseid meteors atop Shi Keng Kong peak in Guangdong province
On March 28, 2017, photographer Jeff Miles captured four gigantic jets over Australia.
On July 24, 2017, the Gemini Cloudcam at the Mauna Kea Observatory in Hawaii captured several gigantic jets as well as ionosphere-height gravity waves during one thunderstorm.
On October 16, 2019, pilot Chris Holmes captured a high-resolution video of a gigantic jet from above the Gulf of Mexico near the Yucatán Peninsula.[
]
/ref> From , Holmes's video shows a blue streamer reach up from the top of a thunderstorm to the ionosphere, becoming red at the top. Only then does a brilliant white lightning leader crawl slowly from the top of the cloud, reaching about 10% of the height of the gigantic jet before fading.
On September 20, 2021, at 10:41 pm (02:41 UTC) facing NE from Cabo Rojo, Puerto Rico, photographer Frankie Lucena recorded a video of a gigantic jet plasma event which occurred over a thunderstorm in the area.
On 15 February 2024, photographer JJ Rao ( Nature by JJ) captured a gigantic jet in high-resolution slow-motion video from Derby, in the Kimberley Region of Western Australia.
Other types
Elves
ELVES often appear as a dim, flattened, expanding glow around in diameter that lasts for, typically, just one millisecond.[ ELVES, a primer: Ionospheric Heating By the Electromagnetic Pulses from Lightning] They occur in the ionosphere sea level over . Their color was unknown for some time, but is now known to be red. ELVES were first recorded on another shuttle mission, this time recorded off French Guiana on October 7, 1990.
ELVES is a whimsical acronym for emissions of light and very Low frequency due to electromagnetic pulse sources.[ The Free Dictionary – ELVES] This refers to the process by which the light is generated; the excitation of nitrogen molecules due to electron collisions (the electrons possibly having been energized by the Electromagnetism pulse caused by a discharge from an underlying thunderstorm).
Trolls
TROLLs (transient red optical luminous lineaments) occur after strong sprites, and appear as red spots with faint tails, and on higher-speed cameras, appear as a rapid series of events, starting as a red glow that forms after a sprite tendril, that later produces a red streak downward from itself. They are similar to jets.
Pixies
Pixies were first observed during the STEPS program during the summer of 2000, a multi-organizational field program investigating the electrical characteristics over thunderstorms on the High Plains. A series of unusual, white luminous events atop the thunderstorm were observed over a 20-minute period, lasting for an average of 16 milliseconds each. They were later dubbed 'pixies'. These pixies are less than 100 meters across, and are not related to lightning.
Ghosts
Ghosts (greenish optical emission from sprite tops) are faint, green glows that appear within the footprint of a red sprite, persisting after the red has dissipated and re-igniting with the onset of subsequent sprite events.
The first spectroscopy study to analyze the dynamics and chemistry of ghosts was led by the Atmospheric Electricity group of the Institute of Astrophysics of Andalusia (IAA). This experimental campaign reported the main contributors to the greenish hue of a single event recorded in 2019 to be atomic iron and nickel, molecular nitrogen and ionic molecular oxygen. A weak -but certain- contribution of atomic oxygen, and atomic sodium and ionic silicon were also detected.
Gnomes
A gnome is a type of lightning that is a small, brief spike of light that points upward from a thunderstorm cloud's anvil top, caused as strong updrafts push moist air above the anvil. It lasts for only a few microseconds.
See also
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Aurora
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Heat lightning
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Schumann resonances
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Sprite (lightning)
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St. Elmo's fire
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Steve (atmospheric phenomenon)
External links
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Homepage of the Eurosprite campaign, itself part of the CAL (Coupled Atmospheric Layers) research group
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March 2, 1999, University of Houston: UH Physicists Pursue Lightning-Like Mysteries Quote: "...Red sprites and blue jets are brief but powerful lightning-like flashes that appear at altitudes of above thunderstorms..."
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Barrington-Leigh, C. P., " ELVES : Ionospheric Heating By the Electromagnetic Pulses from Lightning (A primer)". Space Science Lab, Berkeley.
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" Darwin Sprites '97". Space Physics Group, University of Otago.
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Gibbs, W. Wayt, " Sprites and ELVES : Lightning's strange cousins flicker faster than light itself". San Francisco. ScientificAmerican.com.
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Barrington-Leigh, Christopher, " VLF Research at Palmer Station".
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Sprites, jets and TLE pictures and articles
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High speed video (10,000 frame/s) taken by Hans Stenbaek-Nielsen, University of Alaska
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Video Reveals 'Sprite' Lightning Secrets, Livescience article, 2007.
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Pictures and video of two separate gigantic jets above Oklahoma
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Gigantic jets between a thundercloud and the ionosphere.
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Huge Mystery Flashes Seen In Outer Atmosphere
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Sprite Gallery
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http://webarchive.loc.gov/all/20020914103454/http://elf.gi.alaska.edu/
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The Endless, Short film inspired by Sprite
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Cloud Flashes ZT Research
