Bizarre giant "candles", bright spots of light and structures similar to flying saucers appear in the sky during thunderstorms as a result of the action of atmospheric gravitational waves on clouds, physicists say in an article published in the journal Nature Communications.
The existence of a kind of "UFO" generated by lightning strikes was predicted back in 1924 by Nobel laureate Charles Wilson, the creator of the famous "camera" for detecting elementary particles, but the first such "candles", or "sprites" (ghosts in English), were photographed randomly only in 1989.
By their nature, they are powerful discharges of electricity that occur at an altitude of 50-100 kilometers and extend for several tens of kilometers in length and width. “UFOs” usually appear for a very short time - about one hundred milliseconds - after being struck by particularly strong lightning. Due to the very high brightness, these "ghosts" are easy to see with the naked eye if you know where to look.
Ningyu Liu of Florida State University in Melbourne (USA) and his colleagues uncovered the nature of these unusual flares by creating a computer model of electric UFOs using data collected from aerial and ground observations of their formation in the upper atmosphere.
As the calculations of the Liu group showed, "sprites" arise during thunderstorms due to how atmospheric gravitational waves affect the state of the electric field that exists above and below thunderclouds.
Unlike their elusive cosmological "namesakes", the cause of atmospheric gravitational waves and how they affect the Earth are well known to scientists. They arise as a result of the interaction of large atmospheric fronts with mountain ranges and other large natural barriers. Traces of their existence can be seen in waves on the surface of a calm sea, cirrus clouds and in some other phenomena.
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When such waves hit the upper atmosphere, they often generate strong disturbances. In turn, these disturbances can appreciably shape the electric field around thunderclouds. As Liu and his colleagues found out, at a certain strength and frequency of vibration, they generate "UFOs."
“Disturbances of small size and large amplitude are ideal parents for 'sprites'. If the size of the disturbances is too large, then the "UFO" simply will not appear. If the range of fluctuations is not very high, then the "ghosts" are formed extremely reluctantly and slowly,”explains Liu.
Scientists believe that similar mechanisms of formation may be characteristic of other "light-electric" shows, which often occur in the upper atmosphere and have not yet been explained. An example of this, according to physicists, can be a mysterious glow in the upper atmosphere, whose source can also be lightning strikes.