The earliest known report of transient optical phenomena above thunderclouds is from [[Johann Georg Estor]] in 1730. Another early report is by Toynbee and Mackenzie in 1886.<ref name="samTM">{{cite journal |last=Toynbee |first=Henry |title=Meteorological phenomena (letter) |journal=Nature |volume=33 |issue=846 |page=245 |date=14 January 1886 |doi=10.1038/033245d0|s2cid=4128139 |url=https://zenodo.org/record/1698249|doi-access=free }}</ref> Nobel laureate [[Charles Thomson Rees Wilson|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]], using a low-light video camera, accidentally captured the first image of what would subsequently become known as a sprite.<ref name="aaas">{{Cite journal |doi=10.1126/science.249.4964.48 | title=Television Image of a Large Upward Electrical Discharge Above a Thunderstorm System | date=1990 | first1=R.C.|last1=Franz | first2=R.J.|last2=Nemzek | first3=J.R.|last3=Winckler | journal=Science|volume=249|issue=4964|pages=48–51| pmid=17787625 | bibcode=1990Sci...249...48F | s2cid=9343018}}</ref>
The earliest known report of transient optical phenomena above thunderclouds is from [[Johann Georg Estor]] in 1730. Another early report is by Toynbee and Mackenzie in 1886.<ref name="samTM">{{cite journal |last=Toynbee |first=Henry |title=Meteorological phenomena (letter) |journal=Nature |volume=33 |issue=846 |page=245 |date=14 January 1886 |doi=10.1038/033245d0|s2cid=4128139 |url=https://zenodo.org/record/1698249|doi-access=free }}</ref> Nobel laureate [[Charles Thomson Rees Wilson|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]], using a low-light video camera, accidentally captured the first image of what would subsequently become known as a sprite.<ref name="aaas">{{Cite journal |doi=10.1126/science.249.4964.48 | title=Television Image of a Large Upward Electrical Discharge Above a Thunderstorm System | date=1990 | first1=R.C.|last1=Franz | first2=R.J.|last2=Nemzek | first3=J.R.|last3=Winckler | journal=Science|volume=249|issue=4964|pages=48–51| pmid=17787625 | bibcode=1990Sci...249...48F | s2cid=9343018}}</ref>
Several years after their discovery they were named [[sprite (creature)|sprite]]s (air spirits) after their elusive nature.<ref name="sentman">{{cite journal | doi = 10.1029/95GL00583 | last1 = Sentman | first1 = D.D. | last2 = Wescott | first2 = E. M. | last3 = Osborne | first3 = D. L. | last4 = Hampton | first4 = D. L. | last5 = Heavner | first5 = M. J.| title = Preliminary results from the Sprites94 aircraft campaign: 1. Red Sprites | journal = Geophys. Res. Lett. | volume = 22 | issue = 10 | pages = 1205–1208| date = 1995 | bibcode=1995GeoRL..22.1205S}}</ref> 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.
Several years after their discovery they were named [[sprite (creature)|sprite]]s (air spirits) after their elusive nature.<ref name="sentman">{{cite journal | doi = 10.1029/95GL00583 | last1 = Sentman | first1 = D.D. | last2 = Wescott | first2 = E. M. | last3 = Osborne | first3 = D. L. | last4 = Hampton | first4 = D. L. | last5 = Heavner | first5 = M. J.| title = Preliminary results from the Sprites94 aircraft campaign: 1. Red Sprites | journal = Geophys. Res. Lett. | volume = 22 | issue = 10 | pages = 1205–1208| date = 1995 | bibcode=1995GeoRL..22.1205S}}</ref> 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. Despite being recorded in photographs and videos for the more than 30 years, according to NASA's APOD blog, the "root cause" of sprite lightning remains unknown, "apart from a general association with positive cloud-to-ground lightning."<ref>{{cite web |title=Sprite Lightning at 100,000 Frames Per Second |url=https://apod.nasa.gov/apod/ap210104.html |website=APOD.NASA.gov |publisher=NASA's APOD (Astronomy Picture of the Day blog) |access-date=19 July 2022}}</ref>
In 2016, sprites were observed during [[Hurricane Matthew|Hurricane Matthew's]] passage through the Caribbean.<ref name="vqwzi">{{cite news|newspaper=National Geographic|date=October 3, 2016|access-date=October 3, 2016|title=Rare, Colorful Lightning Sprites Dance Over Hurricane Matthew|url=http://news.nationalgeographic.com/2016/10/lightning-sprites-form-over-hurricane-matthew/}}</ref> The role of sprites in the tropical cyclones is presently unknown.<ref name="CIMSSOct2">{{cite web|publisher=University of Wisconsin–Madison|work=Cooperative Institute for Meteorological Satellite Studies|date=October 7, 2016|access-date=November 3, 2016|title=Hurricane Matthew and the Day/Night Band|url=http://cimss.ssec.wisc.edu/goes/blog/archives/date/2016/10/02}}</ref>
In 2016, sprites were observed during [[Hurricane Matthew|Hurricane Matthew's]] passage through the Caribbean.<ref name="vqwzi">{{cite news|newspaper=National Geographic|date=October 3, 2016|access-date=October 3, 2016|title=Rare, Colorful Lightning Sprites Dance Over Hurricane Matthew|url=http://news.nationalgeographic.com/2016/10/lightning-sprites-form-over-hurricane-matthew/}}</ref> The role of sprites in the tropical cyclones is presently unknown.<ref name="CIMSSOct2">{{cite web|publisher=University of Wisconsin–Madison|work=Cooperative Institute for Meteorological Satellite Studies|date=October 7, 2016|access-date=November 3, 2016|title=Hurricane Matthew and the Day/Night Band|url=http://cimss.ssec.wisc.edu/goes/blog/archives/date/2016/10/02}}</ref>
Revision as of 14:50, 19 July 2022
Electrical discharges above thunderstorm clouds
First color image of a sprite, taken from an aircraftA sprite seen from the International Space Station (top right, faint red above the lightning).
Sprites or red sprites are large-scale electric discharges that occur high above thunderstorm clouds, or cumulonimbus, 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.
Sprites appear as luminous red-orange flashes. They often occur in clusters above the troposphere at an altitude range of 50–90 km (31–56 mi). Sporadic visual reports of sprites go back at least to 1886[clarification needed][1] but they were first photographed on July 4, 1994, by scientists from the University of Minnesota and have subsequently been captured in video recordings many thousands of times.
The earliest known report of transient optical phenomena above thunderclouds is from Johann Georg Estor in 1730. Another early report is by Toynbee and Mackenzie in 1886.[2] 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, using a low-light video camera, accidentally captured the first image of what would subsequently become known as a sprite.[3]
Several years after their discovery they were named sprites (air spirits) after their elusive nature.[4] 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. Despite being recorded in photographs and videos for the more than 30 years, according to NASA's APOD blog, the "root cause" of sprite lightning remains unknown, "apart from a general association with positive cloud-to-ground lightning."[5]
In 2016, sprites were observed during Hurricane Matthew's passage through the Caribbean.[6] The role of sprites in the tropical cyclones is presently unknown.[7]
Characteristics
Different types of electrical phenomena in the atmosphere
Rodger (1999) categorized three types of sprites based on their visual appearance.[1]
Jellyfish sprite – very large, up to 50 by 50 km (31 by 31 mi).
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[4] in their upper regions, with bluish hanging tendrils 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,[11] although sprites generated by negative ground flashes have also been observed.[12] They often occur in clusters of two or more, and typically span the altitude range 50 to 90 kilometres (31 to 56 mi), with what appear to be tendrils hanging below, and branches reaching above.[4]
A sprite over Laos, as seen from the International Space Station
Optical imaging using a 10,000 frame-per-second high speed camera showed that sprites are actually clusters of small, decameter-sized (10–100 m or 33–328 ft) balls of ionization that are launched at an altitude of about 80 km (50 mi) and then move downward at speeds of up to ten percent the speed of light, followed a few milliseconds later by a separate set of upward moving balls of ionization.[13] Sprites may be horizontally displaced by up to 50 km (31 mi) 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.
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: 150–500 km (93–311 mi) of clear view to a powerful thunderstorm with positive lightning between cloud and ground, red-sensitive recording equipment, and a black unlit sky.[14]
Sprite halo
Sprites are sometimes preceded, by about 1 millisecond, by a sprite halo, a pancake-shaped region of weak, transient opticalemissions approximately 50 kilometres (31 mi) across and 10 kilometres (6.2 mi) thick. The halo is centered at about 70 kilometres (43 mi) 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, due to their visual similarity and short duration.[15][16][17]
Research carried out at Stanford University 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.[17]
Research in 2004 by scientists from Tohoku University found that very low frequency emissions occur at the same time as the sprite, indicating that a discharge within the cloud may generate the sprites.[18]
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 NASAstratospheric balloon launched on June 6, 1989, from Palestine, Texas. The balloon suffered an uncommanded payload release while flying at 120,000 feet (37,000 m) over a thunderstorm near Graham, Texas. Months after the accident, an investigation concluded that a "bolt of lightning" traveling upward from the clouds provoked the incident.[19] The attribution of the accident to a sprite was made retroactively, since this term was not coined until late 1993.
^ abcSentman, D.D.; Wescott, E. M.; Osborne, D. L.; Hampton, D. L.; Heavner, M. J. (1995). "Preliminary results from the Sprites94 aircraft campaign: 1. Red Sprites". Geophys. Res. Lett. 22 (10): 1205–1208. Bibcode:1995GeoRL..22.1205S. doi:10.1029/95GL00583.
^"Hurricane Matthew and the Day/Night Band". Cooperative Institute for Meteorological Satellite Studies. University of Wisconsin–Madison. October 7, 2016. Retrieved November 3, 2016.
^Lu, Gaopeng; Cummer, Steven A; Blakeslee, Richard J; Weiss, Stephanie; Beasley, William H (2012). "Lightning morphology and impulse charge moment change of high peak current negative strokes". Journal of Geophysical Research: Atmospheres. 117 (D4): n/a. Bibcode:2012JGRD..117.4212L. CiteSeerX10.1.1.308.9842. doi:10.1029/2011JD016890.