Scientists from Nizhny Novgorod have created a sprite tracking system
Real high-altitude flare hunters — «spirits of the air» (or sprites) from the Institute of Applied Physics of the Russian Academy of Sciences recreated the object of their study in the laboratory. In a small vacuum chamber, they caught a fleeting «spirit» that existed for hundredths of a second, similar to those that usually occur at altitudes above 50 kilometers above the Earth, above thunderclouds. About what other «essences» can appear in the sky, why they need to be investigated, we talked with the author of the project, Candidate of Physical and Mathematical Sciences Andrei Yevtushenko.
Lab born sprite. Photo courtesy of IAP RAS
Even 30 years ago, someone who described such phenomena could be called an eccentric, because few people believed in the existence of «sprites»; (from Lat spiritus – «spirit»), elves and other atmospheric fairy tale characters. There are two reasons why strange high-altitude flares have managed to hide from scientists for a long time. Firstly, they are almost impossible to see with the naked eye, because they are very short-lived, that is, they occur in 10-15 milliseconds, which is more fleeting than the change of the 25th frame. Secondly, they flare up only on the other side of the clouds, and in order to fix them with the help of the highest-speed camera, one must also find a convenient position, for example, by chance to be on an airplane flying above the clouds. Thirdly, modern video cameras capable of «catching» these amazing flashes have appeared relatively recently.
The first to discover high-altitude flares was Professor John Randolph Winkler, a 73-year-old NASA veteran. It happened in 1989. The scientist pointed a video camera at thunderclouds, and then, looking through the film frame by frame, he discovered bright flashes that, unlike ordinary lightning, occurred above the clouds. «Show» occurred between 14 and 40 kilometers above the Earth's surface.
After Winkler's discovery was confirmed by other researchers, a boom in research in this area began. It soon became clear that the «inhabitants» The reverse side of the clouds is many: they were classified (as their height and shape increased) into jets, sprites, halos and elves.
– Let's start with those that arise below all the rest. These are jets (from the English «jet» — jet) – high-altitude flashes, which are also called reverse lightning, which are discharged from the cloud not towards the earth, but towards the sky. Jets are characterized by a blue color (it depends on the density of the atmosphere at those altitudes where flashes occur). Jets are divided into blue starters that «shoot» up to 20-25 kilometers upwards, to classic jets that reach 50 kilometers, and giant jets that can stretch up to 90 kilometers). At altitudes from 50 to 90 km, sprites appear that already have red or pink colors. These flashes directly depend on the parent ordinary lightning (they are, as it were, its echo from the back of a thundercloud). They are also different. For the outward resemblance of some to jellyfish, «tentacles» which are directed to the ground, they are called – «jellyfish sprite». Others are more shaped like carrots – «carrot sprite”. There is also a halo — a diffuse, diffused glow that forms instead of a sprite. And finally, the elves. They also occur at high altitudes of about 85-90 km, are red in color and represent the reaction of the atmosphere to an electromagnetic pulse coming from a conventional lightning discharge. Notice the «elf» even harder than jets and sprites, – it occurs, on average, for one millisecond. But thanks to the high-speed cameras that filmed them, we know they are – a radially diverging ring at altitudes of about 90 km, a kind of expanding luminous steering wheel.
— They occur more often than other phenomena. In addition, our work on the development of sprite maps and their modeling did not start from scratch, – so far, we have studied ordinary lightning and atmospheric currents. And sprites directly depend on them (which cannot be said about jets that are born on their own).
Estimated sprite density map. Provided by IAP RAS
– We built a vacuum chamber with a volume of 4 cubic meters, installed two electrodes in it to bring the potential and created a pressure close to what occurs in the mesosphere, where natural sprites are born (it is several thousand times less than that in which we live with you). But the subtlety is that in nature pressure in different areas of the distribution of the discharge – miscellaneous. That is why sprites take the form of either jellyfish or carrots. And in order to achieve similarity, we also set a goal for ourselves: to create pressure drops in our installation.
– Ours was more like a carrot.
– Various high-altitude flares are more common in the tropics and subtropics, where the most active convection events occur (active vertical heat transfer in the atmosphere — Auth.). These are the Caribbean, Southeast Asia, Africa, the Mediterranean.
– Sometimes they are found in our latitudes. One of my colleagues once took a photo of a sprite from Moscow. True, the cloud over which it arose was at that moment approximately over Tver.
– Such events only in this way «catch». To catch a sprite (or jet), you need to be where there is no thunderstorm and a clear sky above your head. You need to look where powerful thunderstorm activity is observed at a distance of about 100-200 km. Then there will be a high chance of capturing a sprite with a highly sensitive camera.