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Sprites or red sprites are large-scale electric discharges that occur in the
mesosphere The mesosphere (; ) is the third layer of the atmosphere, directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as altitude increases. This characteristic is used to define limits: it be ...
, high above
thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...
clouds, or
cumulonimbus Cumulonimbus () is a dense, towering, vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents. Above the lower portions of the cumulonimbus the water va ...
, giving rise to a varied range of visual shapes flickering in the night sky. They are usually triggered by the discharges of positive lightning between an underlying thundercloud and the ground.


Precis

Sprites appear as luminous red-orange flashes. They often occur in clusters above the
troposphere The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...
at an altitude range of . Sporadic visual reports of sprites go back at least to 1886. They were first photographed on July 4, 1989, by
scientists A scientist is a person who researches to advance knowledge in an area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engaged in the philosophical study of nature ...
from the
University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...
and have subsequently been captured in video recordings thousands of times. Sprites are sometimes inaccurately called upper-atmospheric lightning. However, they are cold plasma phenomena that lack the hot channel temperatures of tropospheric lightning, so they are more akin to
fluorescent tube A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor ...
discharges than to lightning discharges. Sprites are associated with various other upper-atmospheric
optical phenomena Optical phenomena are any observable events that result from the interaction of light and matter. All optics, optical phenomena coincide with Quantum mechanics, quantum phenomena. Common optical phenomena are often due to the interaction of ligh ...
including blue jets and
ELVES An elf (: elves) is a type of humanoid supernatural being in Germanic folklore. Elves appear especially in North Germanic mythology, being mentioned in the Icelandic ''Poetic Edda'' and the ''Prose Edda''. In medieval Germanic-speakin ...
. ISS-44 Red Sprites, northwest Mexico.jpg, A sprite at the horizon, with lightning below in the
troposphere The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...
and above the green line of
airglow Airglow is a faint emission of light by a planetary atmosphere. In the case of Earth's atmosphere, this optical phenomenon causes the night sky never to be completely dark, even after the effects of starlight and diffuse sky radiation, diffuse ...
at the upper mesopause and border to space (the bright light above is the Moon). bigRed-Sprite.jpg, First color image of a sprite, taken from an aircraft sprite seen from space.jpg, A sprite over
Laos Laos, officially the Lao People's Democratic Republic (LPDR), is the only landlocked country in Southeast Asia. It is bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the southeast, and Thailand to the west and ...
, as seen from the International Space Station


History

The earliest known report is by Toynbee and Mackenzie in 1886. Nobel laureate C. T. R. Wilson had suggested in 1925, on theoretical grounds, that electrical breakdown could occur in the upper atmosphere, and in 1956 he witnessed what possibly could have been a sprite. They were first documented photographically on July 6, 1989, when scientists from the
University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...
, using a low-light video camera, accidentally captured the first image of what would subsequently become known as a sprite. Several years after their discovery they were named sprites (air spirits) after their namesake mythological entity based on their elusive nature. Since the 1989 video capture, sprites have been imaged from the ground, from aircraft and from space, and have become the subject of intensive investigations. A featured high speed video that was captured by Thomas Ashcraft, Jacob L Harley, Matthew G McHarg, and Hans Nielsen in 2019 at about 100,000 frames per second is fast enough to provide better detailing of how sprites develop. However, according to NASA's APOD blog, despite being recorded in photographs and videos for the more than 30 years, the "root cause" of sprite lightning remains unknown, "apart from a general association with positive cloud-to-ground lightning." NASA also notes that not all storms exhibit sprite lightning. In 2016, sprites were observed during Hurricane Matthew's passage through the Caribbean. The role of sprites in the tropical cyclones is presently unknown.


Characteristics

upperatmoslight1.jpg, Different types of electrical phenomena in the atmosphere sprite from ISS.jpg, A sprite seen from the International Space Station (top right, faint red above the lightning) sprite from ISS (cropped).jpg, ISS sprite image above; zoomed in red sprite.jpg, Another shot from the first color clip of the sprite. Sprites have been observed over
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
,Kathy Berry (1994)
Spectacular Color Flashes Recorded Above Electrical Storms.
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
. Retrieved on 2009-02-18.
Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
,
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
,Don Savage and Kathy Berry (1995)
Sprites Confirmed Over Storms Outside U.S. For First Time.
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
. Retrieved on 2009-02-18.
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
,
Central Africa Central Africa (French language, French: ''Afrique centrale''; Spanish language, Spanish: ''África central''; Portuguese language, Portuguese: ''África Central'') is a subregion of the African continent comprising various countries accordin ...
(
Zaire Zaire, officially the Republic of Zaire, was the name of the Democratic Republic of the Congo from 1971 to 18 May 1997. Located in Central Africa, it was, by area, the third-largest country in Africa after Sudan and Algeria, and the 11th-la ...
),
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
, the
Sea of Japan The Sea of Japan is the marginal sea between the Japanese archipelago, Sakhalin, the Korean Peninsula, and the mainland of the Russian Far East. The Japanese archipelago separates the sea from the Pacific Ocean. Like the Mediterranean Sea, it ...
and
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
and are believed to occur during most large thunderstorm systems. Rodger (1999) categorized three types of sprites based on their visual appearance. * Jellyfish sprite – very large, up to . * Column sprite (C-sprite) – large-scale electrical discharges above the earth that are still not totally understood. * Carrot sprite – a column sprite with long tendrils. Sprites are colored reddish-orange in their upper regions, with bluish hanging
tendril In botany, a tendril is a specialized Plant stem, stem, leaf or Petiole (botany), petiole with a thread-like shape used by climbing plants for support and attachment, as well as cellular invasion by parasitic plants such as ''Cuscuta''. There ar ...
s below, and can be preceded by a reddish halo. They last longer than normal lower stratospheric discharges, which last typically a few milliseconds, and are usually triggered by the discharges of positive lightning between the thundercloud and the ground, although sprites generated by negative ground flashes have also been observed. They often occur in clusters of two or more, and typically span the altitude range , with what appear to be tendrils hanging below, and branches reaching above. Optical imaging using a 10,000 frame-per-second high speed camera showed that sprites are actually clusters of small, decameter scale, () balls of ionization that are launched at an altitude of about and then move downward at speeds of up to ten percent the
speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...
, followed a few milliseconds later by a separate set of upward moving balls of ionization. Sprites may be horizontally displaced by up to from the location of the underlying lightning strike, with a time delay following the lightning that is typically a few milliseconds, but on rare occasions may be up to 100 milliseconds. upright=1.3, This footage from the ISS shows a red sprite over East Asia immediately before 0:07, directly above the large lightning flash towards the upper right of the frame. In order to film sprites from Earth, special conditions must be present: of clear view to a powerful thunderstorm with positive lightning between cloud and ground, red-sensitive recording equipment, and a black unlit sky.Grønne, Jesper
"Første danske 'red sprites' fanget fra Silkeborg"
''
Danish Meteorological Institute The Danish Meteorological Institute (DMI; ) is the official Danish meteorological institute, administrated by the Ministry of Climate, Energy and Utilities. It makes weather forecasts and observations for Denmark, Greenland, and the Faroe Is ...
'', 20 August 2012. Retrieved: 20 August 2012.


Mechanism

Sprites occur near the top of the
mesosphere The mesosphere (; ) is the third layer of the atmosphere, directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as altitude increases. This characteristic is used to define limits: it be ...
at about 80 km altitude in response to the electric field generated by lightning flashes in underlying thunderstorms. When a sufficiently large positive lightning strike carries charges to the ground, the cloud top is left with a strongly negative net charge. This can be modeled as a quasi-static electric dipole and for less than 10 milliseconds a strong
electric field An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...
is generated in the region above the thunderstorm. In the low pressure of the upper mesosphere the
breakdown voltage The breakdown voltage of an insulator (electrical), insulator is the minimum voltage that causes a portion of an insulator to experience electrical breakdown and become electrically Conductor (material), conductive. For diodes, the breakdown vo ...
is drastically reduced, allowing for an
electron avalanche An electron avalanche is a process in which a number of free electrons in a transmission medium are subjected to strong acceleration by an electric field and subsequently collide with other atoms of the medium, thereby ionizing them ( impact ioniz ...
to occur. Sprites get their characteristic red color from excitation of nitrogen in the low pressure environment of the upper mesosphere. At such low pressures
quenching In materials science, quenching is the rapid cooling of a workpiece in water, gas, oil, polymer, air, or other fluids to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, suc ...
by atomic oxygen is much faster than that of nitrogen, allowing for nitrogen emissions to dominate despite no difference in composition.


Sprite halo

Sprites are sometimes preceded, by about 1 millisecond, by a sprite '' halo'', a pancake-shaped region of weak, transient
optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
emissions approximately across and thick. The halo is centered at about altitude above the initiating lightning strike. These halos are thought to be produced by the same physical process that produces sprites, but for which the ionization is too weak to cross the threshold required for streamer formation. They are sometimes mistaken for
ELVES An elf (: elves) is a type of humanoid supernatural being in Germanic folklore. Elves appear especially in North Germanic mythology, being mentioned in the Icelandic ''Poetic Edda'' and the ''Prose Edda''. In medieval Germanic-speakin ...
, due to their visual similarity and short duration.Rina Miyasato, Hiroshi Fukunishi, Yukihiro Takahashi, Michael J. Taylor, Hans. C. Stenbaek-Nielsen (2002)
Characteristics of Lightning-induced Sprite Halos and Their Generation Mechanisms.
Academic Society Home Village. Retrieved on 2009-02-18.
Christopher Barrington Leigh (2000)

Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...
. Retrieved on 2008-02-18.
Barrington-Leigh, C. P., U. S. Inan, and M. Stanley
"Identification of Sprites and Elves with Intensified Video and Broadband Array Photometry", J. Geophys. Res. 106, No. 2, February, 2001.
/ref> Research carried out at
Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...
in 2000 indicates that, unlike sprites with bright vertical columnar structure, occurrence of sprite halos is not unusual in association with normal (negative) lightning discharges. Research in 2004 by scientists from
Tohoku University is a public research university in Sendai, Miyagi, Japan. It is colloquially referred to as or . Established in 1907 as the third of the Imperial Universities, after the University of Tokyo and Kyoto University, it initially focused on sc ...
found that
very low frequency Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30  kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave ...
emissions occur at the same time as the sprite, indicating that a discharge within the cloud may generate the sprites.


Related aircraft damage

Sprites have been blamed for otherwise unexplained accidents involving high altitude vehicular operations above thunderstorms. One example of this is the malfunction of a
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
stratospheric balloon launched on June 6, 1989, from Palestine, Texas. The balloon suffered an uncommanded payload release while flying at over a thunderstorm near
Graham, Texas Graham is the county seat of and largest city in Young County. As of the 2020 U.S. Census, it has a population of 8,732. History The site was first settled in 1871 by brothers Gustavus A. and Edwin S. Graham, primary shareholders in the Texas E ...
. Months after the accident, an investigation concluded that a "bolt of lightning" traveling upward from the clouds provoked the incident. The attribution of the accident to a sprite was made retroactively, since this term was not coined until late 1993.


See also

* Upper-atmospheric lightning (includes Blue Jets) *
Aurora (astronomy) An aurora ( aurorae or auroras), also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in Earth's sky, predominantly observed in high-latitude regions (around the Arc ...
* Catatumbo lightning * Cosmic ray visual phenomena


References


External links


"Red Sprites & Blue Jets"
– a digital capture of the VHS video distributed in 1994 by the
University of Alaska Fairbanks The University of Alaska Fairbanks (UAF or Alaska) is a public university, public Land-grant university, land-, National Sea Grant College Program, sea-, and National Space Grant College and Fellowship Program, space-grant research university in ...
that popularized the terms * – webpage by
University of Alaska Fairbanks The University of Alaska Fairbanks (UAF or Alaska) is a public university, public Land-grant university, land-, National Sea Grant College Program, sea-, and National Space Grant College and Fellowship Program, space-grant research university in ...

Ground and Balloon-Borne Observations of Sprites and Jets


Space Physics Group, University of Otago
Sprites, jets and TLE pictures and articles

Sprites in Europe: European contributors blog
* *

* Photography websit
Petapixel
posted a link to a very rare and very clear photograph of a sprite taken by photographer Mike Hollingshead. Article a
Photographer Captures Rare Photograph of a Sprite with an Aurora

At the Edge of Space
– a '' NOVA'' program that examines the phenomenon of Sprites
Red Sprites Over Adriatic Sea
Seen from the Czech Republic (14 January 2019) {{DEFAULTSORT:Sprite (Lightning) category:articles containing video clips category:electrical phenomena category:lightning category:terrestrial plasmas