Sprite (weather phenomenon)
In meteorology, a “ Sprite ” (Eng. “ Kobold ”) is a lightning bolt that strikes upwards above a cloud in a thunderstorm to a height of over 100 kilometers. Most of the time, sprites resemble a narrow jet of flame, sometimes they are reminiscent of a mushroom cloud .
Discovery story
Since the phenomena can seldom be observed from the ground, they were only put on record after the start of aviation. For a long time, however, sprites were dismissed as spinning by pilots. So they had kept silent about their observations, partly for fear of mockery .
In the 1960s fighter pilots had observed the phenomena and reported about them when they were deployed in the Vietnam War . For a long time there was little reliable information and only a few photographs; From 1989 onwards, targeted recordings were made from aircraft, in 2003 from the Space Shuttle Columbia .
Manifestations
Red sprites
"Red Sprites" appear as reddish or bright red discharges that run straight upwards and whose lightning channels usually disintegrate into countless ramifications shortly after emerging from the cloud cover, which is why they are also jokingly called "carrot- Sprites ”. Red sprites occur at altitudes of up to 75 km and reach lengths of up to 20 km. The dividing head end of the discharge extends up to 50 km. In some cases the branches discharge themselves one more time, but this time downwards, with a bluish tint appearing. Because of their appearance, such sprites are referred to as " angel sprites " (in German "angel sprites "). The first recordings of Red Sprites date back to 1989, from 1991 they were recorded specifically during various space shuttle missions. The observations made by reconnaissance flights and radar stations on the ground showed that red sprites always only appear above the cloud cover of particularly violent thunderstorms in the area of the mesosphere (55–85 km altitude). They can appear individually or in swarms. Observation with the naked eye only makes sense if the sky in the background of the spectacle is extremely dark, since red sprites, in contrast to so-called blue jets , are much weaker than conventional cloud-to-ground discharges.
There are different theories about the origin of red sprites: The most common one provides that a strong field of tension builds up over the cloud cover, particularly in violent thunderstorms, which, due to soon over-saturation of electrons as a result of collisions with gamma rays from the ionosphere above, discharges by itself .
Blue jets
At a height of around 40 km, white-bluish, flash-flame-like discharges, "blue jets", which last tenths of a second and literally jump out of the cloud cover in the stratosphere, also arise in a similar manner . They tower up to 25 km before they disintegrate. They seem to be independent of cloud-to-ground discharges.
Elves
Another event are “Elves” (German “ Druden ” or “ Elves ”), which appear at an altitude of 60–105 km (area of the mesosphere and thermosphere ) and often appear together with red goblins. They are ring-shaped and spread over the entire area in a radius of up to 500 km in a fraction of a second. First sightings of Elves were documented in 1992.
literature
- Martin Füllekrug, Eugene A. Mareev, Michael J. Rycroft: Sprites, elves and intense lightning discharges . Springer, Berlin 2006, ISBN 1402046286
- Vladimir A. Rakov, Martin A. Uman: Lightning: Physics and Effects . University Press, Cambridge 2007, ISBN 0521035414
- Matthew James Heavner: Optical spectroscopic observations of sprites, blue jets, and elves: inferred microphysical processes and their macrophysical implications . University Press, Fairbanks (Alaska) 2000
- Gavin Pretor-Pinney, Cloud Appreciation Society: The cloudspotter's guide: the science, history, and culture of clouds . Penguin Books, London 2006 (new edition), ISBN 0399532560
Web links
- nasa.gov : Scientists Seek Sprite Light Source
- spiegel.de : The ghost of light video inspires researchers
- Stephen B. Mende, Davis D. Sentman, and Eugene M. Wescott: Lightning between clouds and space. Retrieved November 25, 2015 .
- Spectrum .de: Kobolds and greenhouse gases May 3, 2019
Individual evidence
- ↑ nasa.gov , NASA Goddard Space Flight Center , June 6, 2005, Mike Bettwy: Unlocking the Mystery Behind Lightning's Puzzling Friend , image from: Walter Lyons, FMA Research , Fort Collins , Colorado . August 1, 2017)
- ↑ a b c Gavin Pretor-Pinney, Cloud Appreciation Society: The cloud potter's guide . Page 68.
- ↑ a b see web link Lesch's Kosmos: Heavenly danger zone
- ↑ a b Martin Füllekrug, Eugene A. Mareev, Michael J. Rycroft: sprites, elves and intense lightning discharges. Page 174–179.
- ↑ a b c Vladimir A. Rakov, Martin A. Uman: Lightning: Physics and Effects . Page 482–494.
- ↑ Working group Meteors e. V. , meteoros.de: Blitzarten - Sprites (23 July 2017)