Ultraviolet corona discharges on treetops

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tt-3 about 4 hours ago 35 commentsRead Article on psu.edu

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colanderman•about 3 hours ago

There is in fact no photograph of treetops glowing.

There is a digital UV-wavelength video of the corona, and a visible-wavelength video of the trees.

The paper [1] contains a sole picture with tiny circles indicating where the UV-video detected corona events, overlaid over a frame of the visible-wavelength video.

The paper does also contain a video [2] which overlays a somewhat processed version of the UV video over the visible wavelength video, where UV photon events are indicated by decaying red dots.

[1] https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL11...

[2] https://agupubs.onlinelibrary.wiley.com/action/downloadSuppl...

dang•12 minutes ago

I've taken the "captured on film" out of the title above and used representative language from the article. If someone can suggest a better (more accurate and neutral) title, we can change it again. (But the subject is interesting whether on film or not, let alone "for the first time".)

raincole•about 1 hour ago

That's some weird semantic nitpicking.

Wikimedia has a category of "photographs of the Sun":

https://commons.wikimedia.org/wiki/Category:Photographs_of_t...

Do you think they are not photographs of the Sun because these are not what I see if I look at the sun with my eyes? (In which case I'll see pure white then perma black, I assume.)

latexr•44 minutes ago

> then perma black, I assume.

Probably not.

https://www.bbc.com/news/blogs-ouch-31487662

t-3•17 minutes ago

They're the same as looking at the sun with your eyes. You won't go blind looking directly for a short time. It's just best not to stare for a long time.

Bjartr•26 minutes ago

While we're being unreasonably pedantic, it also wasn't caught on film because it was a digital camera.

addaon•about 2 hours ago

Sorry, in what way is this not a photograph? Are you saying that a video is not a sequence of photographs, that UV photons captured by a sensor don’t count because human retina sensitivity is low in that range, or some hopefully-less-semantic argument?

clickety_clack•about 2 hours ago

The headline suggests that people have seen treetops glowing and it just hasn’t been captured on video before. The actual pictures and video is of something that nobody could have seen with their eyes.

eel•31 minutes ago

This reminds me of a chat room interaction I had maybe 25 years ago. The other person was adamant that humans can't see the infrared from TV remotes, and I was adamant that I could. It was pretty a widespread belief (even in school science books) at that time that humans couldn't see infrared. Since then more science was done to prove that, in fact, some humans can see some infrared under some conditions.

I share that mainly to state that humans are amazing and have a wide and inconsistent range of capabilities (and sometimes even mutating into new capabilities!) Personally, I will always hesitate to say "nobody" and I lean towards "no typical human" instead. :)

WarmWash•about 2 hours ago

You can absolutely see corona discharge like that with your eyes.

If you come to my day job, and we shut off all the lights in the test room, after your eyes adjust in the dark for a minute, you'll see the soft purple glow coming from the edge our 160kV test rig.

Definitely emits UV, but there is enough visible to see it for sure. It comes from the electrons exciting nitrogen in the air.[1]

1. https://commons.wikimedia.org/wiki/File:Nitrogen_discharge_t...

chrisfosterelli•about 2 hours ago

I don't really blame the researchers here but this is yet another article that is happy to have a clickbait headline which any reasonable reader is going to assume will include a picture of "treetops glowing".

At least personally I scanned the article for it and only found the picture at the top, which I was then frustrated to learn that's just a lab photo, and I came here wondering where the actual image is of it in the field so I found OPs comment helpful to indicate that the suggestion there would be a beautiful picture of glowing canopy somewhere is basically a result of editorializing.

adammarples•about 2 hours ago

Maybe they take issue with the word "glowing", which doesn't usually refer to invisible electromagnetic radiation

Brian_K_White•16 minutes ago

I was going to say the same.

It's true that the image isn't fiction or a purely fabricated "artists rendering" from data. But it's also true that "filmed" and "glowing" are unusual ways to refer to what happened.

You don't usually say filmed when talking about recording uv or microwaves etc. You technically could, and probably back when film was actually how uv was recorded a few people working in the field probably did, but almost no one else does, or no one at all since decades, which means the author of the title is the one out of step, not the people reading it.

They actually recorded something, and this title is misleading. Both things are true.

culi•22 minutes ago

Fun fact. Lightning strikes stimulate fungi to produce more mushrooms. Some shiitake and nameko cultivators in Japan have started using electrical shockwaves and gotten dramatically improved yields (sometimes over 200%). Interestingly enough the idea came from Japanese folklore rather than this science

It's possible that this is an evolved response. Lightning hitting a tree will turn it into bark which is an excellent medium for white rot fungi. Lots of mushrooms might maximize the chance to get your spores there. Alternatively, it might mean you're dying soon and should seed out while you can.

We think of lightning strikes as rare events but when it comes to late-successional trees, they are actually one of the main disturbances. Some trees like Dipteryx oleifera have shown fascinating adaptations to lightning strikes. This tree is highly resistant to its negative effects and promotes the growth of many lianas (woody vines) that make it so when the tree is struck, so are many of its neighbors. After being struck it shows dramatically increased growth to outgrow its now-damaged neighbors

chankstein38•about 1 hour ago

I once was about 30-50ft from where lightning struck, standing on my porch looking towards my neighbors' house. I didn't see the actual strike happen but I did feel my hair stand on end and then see basically this coming off of the leaves reaching up towards the sky. Little purple tentacles all reaching upwards.

But then I got to the point in the article where they seemed to explain this wasn't visible to the naked eye.... What did I see?

stronglikedan•36 minutes ago

> I did feel my hair stand on end

I've experienced this when a strike hit power lines above my head. I didn't see the actual strike either - my friend a the other end of the driveway said it was right above me, but that sounds a little hyperbolic to me despite the ringing in my ears. I think we'd both be dead if it were that close. Either way, it gave me a lifelong respect for lightning.

mlhpdx•about 3 hours ago

Having lived in the PNW all my life, and worked closely with our friend Doug (the fir trees), this article brings up old mental images of otherwise healthy needles with browned (dead) tips in the crowns.

Coincidence? Probably.

Very cool phenomenon to catch visually.

t-3•about 2 hours ago

Maybe not a coincidence! The previous research linked in the article mentions this in lab testing:

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JD03...

  > Visually, the corona discharges generated on the leaves were either small purple-blue point discharges or elongated purple-blue discharges, and usually formed on the tips of the leaf closest to the source of the electric field (Figure 1). Sometimes the corona discharges were steady and constant, but other times they would dim and brighten in an unsteady pulse. When the corona was turned off, the tips of the leaf where the discharges occurred were often burned and browned, even for the weakest electric fields applied to the leaves.

Lalabadie•about 3 hours ago

Great time to read about St Elmo's Fire!

https://en.wikipedia.org/wiki/St._Elmo's_fire

_joel•about 3 hours ago

Sounds like a man in motion :)

ortusdux•about 2 hours ago

It would be amazing if there was an electrical mechanism behind crown shyness.

https://en.wikipedia.org/wiki/Crown_shyness

calibas•about 3 hours ago

I notice the article, the paper, and the "plain language" summary of the paper don't mention the common term for this phenomenon, St Elmo's fire.

antimora•about 1 hour ago

> “This just goes to show that there’s still discovery science being done,” said McFarland, lead author on the paper. “For more than half a century, scientists have theorized that corona exists, but this proves it.”

"proves it" ?? What kind of science is that?

867-5309•34 minutes ago

> They chose the Sunshine State because of its propensity to produce frequent thunderstorms

made me giggle

GolfPopper•about 2 hours ago

Reading the article about the unknowns here, how the electrical field interacts with the trees, and what role the produced hydroxyl plays in the atmosphere, makes me think about how daunting the idea of building a sustainable, human-friendly ecosystem off-Earth is.

dreamlayers•about 2 hours ago

What is new here? I thought corona discharges during storms had already been well known for a long time. https://en.wikipedia.org/wiki/St._Elmo%27s_fire

none2585•about 2 hours ago

Article claims it had never been seen outside the lab before (for trees specifically I guess)

imzadi•about 2 hours ago

I've seen these images before, or some very similar images. So this is based on old photos or it has indeed been done before.

dylan604•15 minutes ago

A lot of the PopSci sites rotate articles so that one will publish something followed by another some time later.

Also: "made their way down the nation’s eastern coast in June 2024", so it's possible the PopSci articles were based on early releases about this study and this is the actual study being finalized and released officially????

wildylion•about 3 hours ago

Storm troopers, but not the kind you'd expect.

brador•about 2 hours ago

Will head hair on humans do this too?

dylan604•15 minutes ago

Wouldn't we smell it if it did?