Radiation astronomy/Lightnings

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Representation of upper-atmospheric lightning and electrical-discharge phenomena are displayed. Credit: Abestrobi.

Lightning is more than ground-to-cloud electron transfer.

Thunderstorms[edit]

There is "a decrease in thunderstorms at the time of high cosmic rays and an increase in thunderstorms 2-4 days later."[1]

Elves[edit]

"A third phenomenon was discovered in video from the STS-41 mission (October 1990) in the lower ionosphere directly above an active thunderstorm. It consisted of a large horizontal brightening several hundred kilometers across at the altitude of the airglow layer. In 1995, Lyons and associates confirmed the existence of this type of very brief brightening which they named Emissions of Light and Very Low Frequency Perturbations From Electromagnetic Pulse Sources (ELVES)."[2]

"When the lightning phenomena were viewed from a different vantage point - from above the thunderstorms (e.g., from space, aircraft or mountaintop) - new discoveries were made and insights gained into the upper atmospheric optical flashes now commonly referred to as sprites, jets, starters, and ELVES."[2]

"There are no historical reports from eyewitnesses describing the phenomenon that is now called "Emission of Light and Very Low Frequency Perturbations From Electro-magnetic Pulse Sources" or ELVES (Lyons and Nelson, 1995). The one millisecond lifetime of this phenomenon explains why there have been no eyewitness accounts describing a brief flash that would fill the entire night sky for any observer within a 100 km radius from the causative lightning flash. Inan (1990) and Inan et al. (1991) predicted the existence of strong Joule heating of the base of the ionosphere by the electromagnetic pulses of natural lightning."[2]

"After fifteen sprites and one jet had been identified in the shuttle video, a distinctively different event was discovered in shuttle video acquired on October 7, 1990 directly above an active thunderstorm off the coast of French Guyana (Boeck et al., 1992). A large horizontal flash appeared at the altitude of the airglow layer. It occurred in the video field before the appearance of main lightning flash in a thunderstorm that was near the limb of the Earth. They concluded that the causative lightning flash occurred slightly after the video scan passed the location of the storm image. There was a clear view of the mesosphere below the airglow layer, but there was no indication of a sprite in the video sequence (although a sprite event was captured 4½ hours earlier under similar moonlight conditions). A search of the shuttle video failed to produce a second example of this type of horizontal flash. Since it was clear that this was not an example of a sprite or a jet, the observations were published on the basis of this single example. The video was presented at the 1991 Spring AGU meeting (Boeck et al., 1991a) as well as at the Aerospace Lightning Conference (Boeck et al., 1991b). To promote a better understanding of these new phenomena as seen from space, Vaughan distributed a number of video tapes to various researchers who had express an interest in the phenomena. Seminars based on the video tape observations were given at Los Alamos National Laboratory and Stanford University. Researchers at both of these institutions have made major contributions to the theory of Sprite and ELVES phenomena."[2]

"Several years passed before there was a second successful measurement of the ELVES phenomenon. On June 23, 1995 Lyons et al. (1995) and Fukunishi et al. (1996) confirmed the existence of a flash similar to the airglow flash seen earlier in the shuttle data, and Lyons et al. (1995) gave it the name Emissions of Light and Very Low Frequency Perturbations From Electromagnetic Pulse Sources (ELVES). Lyons presented video images captured by a low-light-level TV camera sited near Ft. Collins, Colorado. The ELVES phenomenon has a characteristic event duration of one millisecond (Fukunishi, 1996)."[2]

Sprites[edit]

This is the first color image of a sprite. Credit: Eastview.
The image shows an example of jellyfish lightning or sprites. Credit: H. H. C. Stenbaek-Nielsen.

"The phenomenon, now known as a sprite, was first accidently documented on ground based videotape recordings on the night of July 6, 1989. Video observations from the space shuttle acquired from 1989 through 1991 provided 17 additional examples to confirm the existence of the sprites phenomenon."[2]

"Throughout the historical scientific literature, there are sprinklings of eyewitness accounts of unusual "lightning" observed in the clear air above nighttime thunderstorms. The descriptions use phases such as "continuous darts of light... ascended to a considerable altitude, resembling rockets more than lightning." (MacKenzie and Toynbee, 1886), "a luminous trail shot up to 15 degrees or so, about as fast as, or faster than, a rocket" (Everett, 1903), "a long weak streamer of a reddish hue" (Malan, 1937), "flames appearing to rise from the top of the cloud" (Ashmore, 1950), or "the discharge assumed a shape similar to roots of a tree in an inverted position" (Wood, 1951). Partly because these eyewitness reports of unusual "lightning" appearing above thunderstorms were never captured on film, the lightning science community generally ignored them. The lack of an established vocabulary and the existence of several distinctive phenomena contributed to the variation in the verbal descriptions."[2]

"[Boccippio et al., 1994] has shown that these bright discharges are associated with large amplitude return strokes bringing positive charge downward. In fact, a positive return stroke accompanied the only MLE sprite recorded within range of a ground based lightning detection network. The videos showed that additional discharges continued in the clouds after a sprite for a total mean time of a second, which can be interpreted as evidence for a continuing current. All together, this was strong evidence that the sprite above the thunderstorm was caused, directly or indirectly, by an energetic lightning discharge."[2]

The "range to the sprites was well over 1000 kilometers [...] The width of the sprites varied considerably from very thin or even several thin filaments to broad columns some kilometers across, while the bright "head" (when visible) had dimensions on the order of kilometers."[2]

"The optical and RF measurements collected during the 1994 field campaign rapidly uncovered the basic properties of sprites (Lyons, 1994; Lyons and Williams, 1994; Lyons et al., 1994; Sentman et al., 1994; Sentman et al., 1995; Wescott et al., 1994; Lyons et al., 1995a,b). Other workers (e.g., Boccippio, 1994) established the causal association of sprites with positive cloud-to-ground lightning discharges."[2]

Sprites "are typically associated with low flash rate cells [...] The shuttle videos established that lightning directly or indirectly causes sprites."[2]

The first "color image of a sprite [...] was obtained during a 1994 NASA/University of Alaska aircraft campaign to study sprites. The event was captured using an intensified color TV camera. The red color was subsequently determined to be from nitrogen fluorescent emissions excited by a lightning stroke in the underlying thunderstorm."[3]

"During a thunderstorm, high in the ionosphere, you’ll find an odd variety of lightning that is far above the thunderstorm itself. Jellyfish lightning, also known as sprites, are red flashes of light that last for a few seconds. They can have a wide bell-shaped top and tentacle-like wisps of light at the bottom, resembling a jellyfish."[4]

"In high-speed videos we can see the dynamics of sprite formation and then use that information to model and to reproduce the dynamics."[5]

"These sprites only occur during thunderstorms, though sprites are about three times higher up than storms. [...] the storms are necessary for sprites to occur, they aren’t quite sufficient enough to cause them on their own [...] The tentacle-like tendrils at the bottom were shown to form much faster than the bell-shaped top. [...] localized plasma irregularities can spark the formation of a sprite."[4]

Blue jets[edit]

"In the summer of 1994, Wescott and associates (Wescott et al., 1994; Wescott et al., 1995a,b) confirmed the existence of jets and named the phenomena blue jets when they recorded a very active thunderstorm in Arkansas, USA using both a low-light-level monochrome and a color video cameras. The video was collected during a nighttime research flight using two aircraft that were flying around the thunderstorm. During this flight, color video imagery established that jets are blue in color and sprites are red. A total of 52 jets were seen during a 20-minute time span. The jets developed over several video frames, with a characteristic time of the order of 100 ms and propagation speeds similar to that of a step leader process (i.e., ~ 105 m/s). The video released after this flight proved to be a turning point in establishing wide interest in these phenomena. The spectacular multiple close-up images of these jets completely overshadowed the single, poorly resolved jet observation from the space shuttle."[2]

Blue jets differ from sprites in that they project from the top of the cumulonimbus above a thunderstorm, typically in a narrow cone, to the lowest levels of the ionosphere 40 to 50 km (25 to 30 miles) above the earth. In addition, whereas red sprites tend to be associated with significant lightning strikes, blue jets do not appear to be directly triggered by lightning (they do, however, appear to relate to strong hail activity in thunderstorms).[6] 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 starters[edit]

Blue "starters (Wescott et al., 1995) [are] an upward moving luminous phenomenon closely related to blue jets."[2]

Gigantic jets[edit]

This is a gigantic jet observed over a thunderstorm. Credit: Welias.
This is an image of a gigantic jet above a thunderstorm near the Philippines. Credit: H. T. Su, R. R. Hsu, A. B. Chen, Y. C. Wang, W. S. Hsiao, W. C. Lai, L. C. Lee, M. Sato & H. Fukunishi.

"On February 02, 2014, the Oro Verde Observatory (República Argentina) reported 10 or more gigantic jet event[s] observed over a thunderstorm in Entre Ríos south. Storm center [is] located at 33°S, 60°W, near the Rosario city."[7]

Each gigantic "jet could transfer 30 coulombs of negative charge from the clouds to the ionosphere (H T Su et al. 2003 Nature 423 974)."[8]

"During a thunderstorm in the South China Sea in July 2002, Su and co-workers used low-light-level cameras to photograph the clouds every 17 milliseconds. The five jets they observed - dubbed carrot-jets or tree-jets according to their shapes - were visible for some tens of milliseconds. But crucially, the team also detected simultaneous bursts of radio waves in four of the five cases, which indicates that the jets had transferred significant amounts of charge. The thunderclouds were at an altitude of 16 km."[8]

"Such electromagnetic bursts have only previously been linked with powerful lightning strikes, which are known to transfer large quantities of charge. But [lightning may not have] triggered the radio waves they detected, since the local lightning detection network registered no strikes at the times of the jets."[8]

On the left is an image of a fully developed gigantic jet above a thunderstorm near the Philippine.

Gamma rays[edit]

The red dots show some of the ~500 terrestrial gamma-ray flashes daily detected by the Fermi Gamma-ray Space Telescope through 2010. Credit: NASA/Goddard Space Flight Center.

"A number of observations by space-based telescopes have revealed ... gamma ray emissions ... terrestrial gamma-ray flashes (TGFs). These observations pose a challenge to current theories of lightning, especially with the discovery of the clear signatures of antimatter produced in lightning.[9]

A TGF has been linked to an individual lightning stroke occurring within 1.5 ms of the TGF event,[10] proving for the first time that the TGF was of atmospheric origin and associated with lightning strikes.

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft, as reported by David Smith of University of California (UC) Santa Cruz, has been observing TGFs at a much higher rate, indicating that these occur about 50 times per day globally (still a very small fraction of the total lightning on the planet). The energy levels recorded exceed 20 MeV. Apparently, the gamma radiation fountains upward from starting points at surprisingly low altitudes in thunderclouds. Steven Cummer, from Duke University's Pratt School of Engineering, said, "These are higher energy gamma rays than come from the sun. And yet here they are coming from the kind of terrestrial thunderstorm that we see here all the time." In 2009, the Fermi Gamma Ray Telescope in Earth orbit observed an intense burst of gamma rays corresponding to positron annihilations coming out of a storm formation. Scientists wouldn't have been surprised to see a few positrons accompanying any intense gamma ray burst, but the lightning flash detected by Fermi appeared to have produced about 100 trillion positrons. This has been reported by media in January 2011, it is an effect, never considered to happen before.[11]

Venus[edit]

During the Soviet Venera program, the Venera 11 and Venera 12 probes detected a constant stream of lightning, and Venera 12 recorded a powerful clap of thunder soon after it landed. The European Space Agency's Venus Express recorded abundant lightning in the high atmosphere.[12]

References[edit]

  1. Mae Devoe Lethbridge (1990). "Thunderstorms, cosmic rays, and solar-lunar influences". Journal of Geophysical Research 95 (D9): 13,645-9. doi:10.1029/JD095iD09p13645. http://www.agu.org/pubs/crossref/1990/JD095iD09p13645.shtml. Retrieved 2012-08-22. 
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 William L. Boeck, Otha H. Vaughan, Jr. and Richard J. Blakeslee, Bernard Vonnegut, and Marx Brook (1994). The Role of the Space Shuttle Videotapes in the Discovery of Sprites, Jets, and Elves. Huntsville, Alabama USA: Global Hydrology Resource Center. Retrieved 2015-04-10.CS1 maint: Multiple names: authors list (link)
  3. Eastview (10 March 2009). File:BigRed-Sprite.jpg. San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2015-04-11. External link in |title= (help)
  4. 4.0 4.1 Lua error in Module:Citation/CS1 at line 3723: bad argument #1 to 'pairs' (table expected, got nil).
  5. Lua error in Module:Citation/CS1 at line 3723: bad argument #1 to 'pairs' (table expected, got nil).
  6. Fractal Models of Blue Jets, Blue Starters Show Similarity, Differences to Red Sprites.
  7. Welias (17 July 2014). File:Giganticjet2.png. San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2015-04-11. External link in |title= (help)
  8. 8.0 8.1 8.2 Katie Pennicott (25 June 2003). Giant jets caught on camera. Institute of Physics. Retrieved 2015-04-11.
  9. Signature Of Antimatter Detected In Lightning - Science News
  10. U.S. Inan, S.C. Reising, G.J. Fishman, and J.M. Horack. On the association of terrestrial gamma-ray bursts with lightning and implications for sprites. Geophysical Research Letters, 23(9):1017-20, May 1996. As quoted by elf.gi.alaska.edu Retrieved 2007-03-06.
  11. http://news.nationalgeographic.com/news/2011/01/110111-thunderstorms-antimatter-beams-fermi-radiation-science-space/
  12. Venus also zapped by lightning. CNN. 29 November 2007. Retrieved 2007-11-29.