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Lightning is such a common phenomenon that people often overlook just how powerful it is (provided it doesn't hit you, obviously). But over the past decade, research has gradually revealed just how extreme lightning is. This everyday phenomenon is powerful enough to produce antimatter and transform atoms, leaving a radioactive cloud in its wake. Understanding how all of this happens, however, is a real challenge, given just how quickly multiple high-energy events take place.
Now, researchers have used an instrument attached to the International Space Station to track the physical processes that are triggered by a lightning strike. The work tracks how energy spreads out from the site of a lightning bolt into the ionosphere via an electromagnetic pulse.
The work relies on a piece of hardware called the Atmosphere–Space Interactions Monitor (ASIM), an ESA-built instrument attached to its lab module on the International Space Station. It's an impressive piece of hardware, tying together two X-ray/gamma-ray detectors, three UV detectors, two optical-wavelength light meters, and two high-speed cameras.
[...] A paper released by Science today describes ASIM's imaging of a single lightning bolt, which took place in 2018 off the coast of Sulawesi in Indonesia. Optical activity heralded the formation of the lightning bolt and started to intensify about 200 microseconds before the gamma rays began registering in the detectors. The gamma rays were primarily in the form of a transient flash lasting about 40 microseconds, but there was a "long" tail of emissions that extended out to 200 microseconds as their energy gradually declined.
UV light started arriving right at the same time that the gamma-ray burst hit. The initial UV light was produced by ionized oxygen as the lightning bolt moves through the atmosphere. But the UV shifted to what's called an "elve," which is a different phenomenon entirely. In the case of elves, the light is the result of an electromagnetic pulse produced by the lightning bolt itself. This travels into the ionosphere, a sparse layer of ionized gasses that starts about 100km above Earth and extends up to roughly where the ISS orbits. Because the pulse takes time to reach the ionosphere, there's a delay between the lightning and the appearance of the elve.
In this case, that delay was about 10 milliseconds, but the elve persisted for a while. That's because the pulse spreads like a balloon being inflated, tracing out an expanding sphere above the Earth. Different areas of the ionosphere get excited as the sphere makes its way through, ultimately causing UV emissions to extend over an area of up to 800 kilometers.
All of this took place in under 300 milliseconds.
Science, 2019. DOI: 10.1126/science.aax3872 (About DOIs).
(Score: 2, Interesting) by Anonymous Coward on Saturday December 14 2019, @06:20AM
My stepfather wrote a book about lightning ...
My daughters were doing some research, yesterday, on their grandfather, Leon Salanave - one of the creators of the Morrison Planetarium, there, at the California Academy of Sciences, in San Francisco's Golden Gate Park.
They found Leon's lightning atlas, for sale, on Amazon. There was only one copy, and it was priced at hundreds of dollars.
https://www.amazon.com/Lightning-Its-Spectrum-Atlas-Photographs/product-reviews/0816503745 [amazon.com]
(I'm not the author of that review, just so we're clear. I can write better than that.)
Let me tell you what it was REALLY like, growing up with lightning.
Leon worked at the University of Arizona, in the Department of Astrophysics, where he taught astronomy classes and did research.
Leon's research - which was graduate level work, even though he only had a Master's degree in astronomy - was to study lightning, which had been a topic of concern in World War II, which was when Leon had first identified the subject as one requiring further research.
When Leon met our mother - a former student at the UofA - he had himself a ramshackle metal building out in the desert, outside Tucson, that he spent much of his time at. It was a two-story building; the second floor was a small metal shack, mounted on wheels. Inside the small shack was a huge camera.
When lightning threatened, Leon would go out to the lab, go up to the small shack, crank open a big panel on the side of the shack, load a huge camera with glass photographic plates, open the shutter, and wait for a lightning strike. After a strike, he would unload the glass plate, put it in a light-tight box, replace it with another unexposed glass photographic plate, and do it again.
As adjuncts to his research, Leon had a radio antenna, with which he could monitor shortwave radio for the sort of static that was associated with lightning storms, and he also had an old Air Force radar that he could pivot about to look at the clouds and see what was going on behind the vapor.
Lest Leon be seen as some sort of pure intellectual being, let me add that he often came back from his desert lab smelling of beer and pretzels. He had a real fondness for these big green bottles of malt liquor, I think it was Rainier Ale, and when I was 16 and it was time to go buy beer for my friends, I, too, found that Rainer Ale was a fast route to not feeling any pain, and that beer, and pretzels, go together really well.
The camera deserves a mention. If you've ever been to Yosemite, to the gift shop, you'll see all these pictures of Ansel Adams, the famous nature photographer, crouching atop an old wood-panelled station wagon that had a photographic platform built atop it. The platform held a camera - but Ansel Adams' camera was huge, with a focal length of 3 or 4 feet - which explained why he needed a mobile photographic platform.
(See https://www.anseladams.org/anadonwostwa1.html [anseladams.org] for one such image.)
Leon used the same sort of camera. He also drove the same sort of car, back in the late 1960s.
When I first saw that picture of Ansel Adams, crouching behind a huge camera that I recognized, perched on top of an old station wagon that I ALSO recognized ... on vacation, in Yosemite, fifty years later ... you could have knocked me over with a feather, my thoughts were spinning so fast.
You see, there's more to this story than meets the eye. When my mother first met Leon, he was ALSO driving an old station wagon, with wood panelling.
I later found out that Ansel Adams was a good friend of Leon's father, Edward Salanave. Edward Salanave had been a hunter and a fisherman and had wandered the San Francisco peninsula, in an old Ford Model A, before World War II. He and Ansel had met, somewhere, and had remained close.
And so it must be pointed out that Ansel Adams was an enormous influence upon Leon Salanave, as he was growing up. It is my analysis that Leon's choice of an old, wood-panelled station wagon and the photographic equipment were both influenced by his father's friend, Ansel Adams.
If you can find a copy of 'Lightning and Its Spectrum', it's worth a read.
I'm sorry Leon is not around to share in the joy of scientific discovery; but if he were, I'm sure he would take pleasure in how his work has helped, and been added to by, other scientists. It must surelly be rewarding to know that one's time has not been wasted.
~childo