Of all the meteorological phenomena that our magnificent planet throws at us, lightning is one of the most spectacular and most mysterious. Although storms are common, we still feel pain in understanding and describing their crackling electrical discharges generated in the sky.
One type of lightning is so rare and rare, in fact, that we didn’t even have concrete evidence to exist until 1990, when researchers identified its “rocket-like” motion in a video shot from the spacecraft’s space shuttle. NASA the year before.
Later called “blue rays,” the rays are now recognized as bright lightning bolts that last a few hundred milliseconds, as lightning strikes from the clouds to the stratosphere.
A blue ray photographed in Hawaii. (Gemini Observatory / AURA / Wikimedia Commons)
We can’t easily see this phenomenon under a curtain of clouds, but that doesn’t mean scientists can’t observe it from above. About 400 kilometers (250 miles) above the planet orbit around the International Space Station, and instruments on board have been watching these mysterious lightnings upside down for some time.
Now, after being installed in 2018, a European Space Station observatory equipped with optical sensors, photometers and gamma and X-ray detectors has recorded five blue flashes from the top of a storm cloud , one of which ended with a ray of blue ray. at the height of the stratosphere.
These rare visions provide valuable information about the appearance of mysterious discharges, according to a team of researchers led by physicist Torsten Neubert of the Technical University of Denmark.
Blue jets are believed to start when a positively charged top of the cloud meets a negatively charged layer at the edge of the cloud and the top layer of air. It is believed to produce an electrical failure that forms a leader: an invisible conductive channel of ionized air through which lightning travels.
However, our understanding of the blue jet leader is quite limited. This is where the data analyzed by Neubert and his team fills gaps.
On February 26, 2019, the Atmosphere-Space Interactions Monitor (ASIM) Observatory recorded five blue flashes, each lasting 10 microseconds, at the top of a storm cloud not far from Nauru Island. in the Pacific Ocean.
One of these flashes produced a blue ray, which reached the stratopause, the interface between the stratosphere and the ionosphere, at an altitude of about 50 to 55 kilometers (about 30 to 34 miles).
In addition, the observatory recorded atmospheric phenomena called ELVES (abbreviation for light emission and very low frequency disturbances due to sources of electromagnetic dust). These are rings of optical and ultraviolet emission expanding into the ionosphere that appear above storm clouds, lasting only about a millisecond, as shown in the following animation.
They are believed to be generated by an electromagnetic pulse at the bottom of the ionosphere, caused by lightning discharge.
The leader’s red issue, however, was weak and very limited. This, the research team said, suggests that the leader himself is very short and localized, compared to fully developed leaders between the ground and the clouds.
This also suggests that flashes and the blue ray itself are a type of discharge coils: branched and twisted sparks coming out of high-voltage sources, such as Tesla coils, in a chain reaction of ionizing air particles.
“We therefore propose that UV pulses are elves generated by serpentine flash currents, rather than by lightning currents,” the researchers write in their article.
They believe the flashes are similar to narrow bipolar events. These are high-power radio frequency discharges that occur inside clouds during storms, which are known to trigger lightning inside the cloud. The team said the blue flashes at the tops of the clouds are probably the optical equivalent of this phenomenon and can turn into blue jets.
Since narrow bipolar events are quite common, this could mean that blue flashes are also more common than we thought. Knowing more about how common they are could make us understand storms and lightning much better, not to mention our atmosphere and all the complex interactions that exist.
The team’s research has been published in Nature.