2023-12-15 17:06:01
Surprising photos of gigantic red shapes in the sky are regularly shared on social networks. The phenomenon of sprites is so extraordinary that some find it hard to believe that it is real: these monstrous shapes, bright and luminous red, seem to have come out of a science fiction film.
This will also interest you
[EN VIDÉO] Discovering the hidden side of storms As spectacular as they are mysterious, sprites belong to the family of transient light phenomena (TLE).
Sprites are very real, and even quite common, including in France. They are most often invisible to the naked eye and are revealed in photos followingwards. However, testimonies have been describing them for hundreds of years, particularly airplane pilots.
But these stories weren’t taken seriously until 1989, when the first photo of sprites was taken unintentionally during a rocket launch. Those also called red spritesleprechauns or red sylphs, are reddish streaks very difficult to see because they are very ephemeral: their lifespan does not exceed a few milliseconds, and sometimes up to a second – which in this case allows them to be seen in real time .
They are part of “transient light phenomena” which also include another extraordinary phenomenon, the blue jet. They occur above the most violent storms and appear when the most powerful lightning strikes (the positive impacts).
This is what we call the “domino effect”: the electrical charge from the lightning under the storm cloud creates a second electrical charge above the cloud. They form between 40 and 145 kilometers of altitude by the reaction of air molecules to the electricity emitted by the storm (ionizing particles).
Why are they red when lightning is white or blue? It is the N2 dinitrogen present at this altitude which gives the red color. The bottom of the sprites, however, is often bluish. They can stretch 50 to 100 kilometers in length or more, but their electrical discharge is weak compared to that of lightning.
They can take various shapes: columns or “carrots”, trails, fireworks, but the most spectacular shape is that of the jellyfish.
Taking photos of sprites requires luck, technique and patience
How can you successfully take a photo of them knowing that the phenomenon is very ephemeral and that there is no guarantee that it will occur in the event of a storm? THE photographer Christophe Suarez is one of the rare French people to have managed to take a photo of it:
« Shooting red sprites is possible thanks to a combination of favorable elements. The prerequisite is the development of cluster storms within a radius of 700 to 800 kilometers and a clear sky between the storm and the photographer. To capture the phenomenon in photos, specialists use very sensitive digital cameras and extremely bright lenses. They take thousands of shots which are then analyzed on the computer, looking for a very faint red glow. A second method is becoming more widespread: the use of very sensitive cameras in video mode. Indeed, at 25 frames/s, an exposure lasts 40ms. The enthusiast produces rushes that can last several minutes. The video images are then extracted using a video editing program. Finally, the image is enhanced using photo development software.”
Most sprite images come from the United States, but they are quite common in Europe too: “ Sprites occur above powerful organized MCS (mesoscale convective system) storms most of the time. This kind of situation happens several times a year in France. Leprechauns can be photographed more than 800 kilometers away, which multiplies the number of possible situations. The south is the most favorable zone in France. Mediterranean storms last longer in autumn and the number of days with clear skies is greater.
1702695299
#Extraordinary #weather #phenomenon #sprites
