Last Friday, October 8, one of the astronauts currently in the International Space Station, Thomas PesquetHe put his camera facing the Earth. The result could have been a random photo of the light pollution exhibit our planet has become. But there was something else. A blue light flash just above Europe caught the photographer’s attention; who, far from being scared, decided to publish the snapshot in Flickr, with a short caption explaining the phenomenon.
It didn’t really give many details. He explained that it is a transient light event, associated with a electric storm, but without explaining what kind. Although we can place our bets; Well, although there is a great variety of them, few fit what is seen in Pesquet’s photo. So let’s see what the options are.
The International Space Station, the ideal place to see them
In his caption, the astronaut explains that this type of phenomenon was described in the past by some airmen. However, no one saw from Earth what they were telling, so it was doubted that they really existed outside the imagination of the pilots.
It was necessary for human beings to begin their first stays in space so that they could see that it was something real. From the International Space Station, more than 300 kilometers above our heads, seeing these events is much easier. So much so that one of the laboratories at its facilities, the Columbus, has instrumentation dedicated to studying them.
But what exactly are they? This question could be answered with detailed information about each of the types that exist. However, they can be broadly defined as very short duration electrical breakdown phenomena, what happens very high in the atmosphere. That is, they occur during thunderstorms, but so high that we cannot see them from the surface. And there are of many types; although, as far as color is concerned, they generally look like blue, green or red light.
Blue, green or red light: from trolls to ‘ghosts’
First of all we find the sprites. These constitute large electrical discharges, which occur high above the storm cloud. They are seen in a wide variety of colors. They are generally one tone oranged Red, although they can also be seen as a blue-green light. In terms of shape, they may have downward hanging tendrils and arched branches above or be preceded by a reddish halo.
They are also very common jets. These are jets of light that are generated as discharges, from the cloud to the air, from rays arising in the troposphere. That is, in the atmospheric layer that is in contact with the Earth’s surface.
On the other hand we meet the elves. Actually his name is ELVES, by acronyms from ANDmission of Light and Very Low Frequency perturbations due to ANDlectromagnetic Pulse Sources. Or, in Spanish, “light emission and very low frequency disturbances due to electromagnetic pulse sources”. They are left with the proper initials of the phrase in English and, voila, an easy to remember name. Regarding its appearance and origin, it is about bursts of light with a very dim glow, flattened and expanding, that last just a millisecond and are formed about 100 kilometers above the ground. They are so faint that until recently their color was not even clear, although they are now believed to be red.
Continuing with the fantastic names, we also find the TROLLS, from the acronym for Transient Red Optical Luminous Lineaments (Transient red optical light lines, in Spanish). These are given after the strongest sprites and they look like red spots, with faint tails.
More acronyms taken from the sleeve: the GHOSTs. They are not called that because they have ghostly shapes (ghost is ghost in English), but by the acronym Green emissions from excited ORxygen in Sprite Tops, which in Spanish means “green emissions of excited oxygen in high sprites”. Are very faint, greenish glows, which appear after the red sprites and fade very quickly, within milliseconds.
And finally, the GNOMES they were baptized that way to continue with the list of fantastic creatures, but not by any specific acronyms. Is about small and short light peaks, of a few microseconds, pointing upwards, at the top of the anvil of a thunderstorm. Very few have been documented, and only in black and white images, so it is not known what color they are.
What did the astronaut see?
In the photograph taken by the astronaut of the International Space Station you see a widened blue flash, which could be due to a blue starter. These are short, bright jets, similar to jets, although they do not form the full blue light jet.
It is the theory that they launch from Science Alert, but it is not safe. What is clear is that nobody or almost nobody should have seen it from Earth and, of course, that it is not dangerous at all. As Pesquet explains, the International Space Station is an ideal place to detect these jets of blue light or of any other color, because it flies over the terrestrial equator, which is the place where the most thunderstorms happen. It is more than normal that they have installed the apparatus there to study them. This is very useful for scientific purposes. But, selfishly speaking, for the rest of the mortals it is a wonder that they can capture and show us photos as wonderful as this one.