Ultraviolet corona discharges on treetops during storms | Hacker News Reader

Ultraviolet corona discharges on treetops during storms

psu.edu

258 pointst-366 comments

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

Ozone: the fast life history signal for the mycelial mind!

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?

> 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.

I've been indirectly hit by lightning, it struck my mom's house while I was running inside from the rain and at least part of it went through the wet iron handrail I was holding and hit me too.

I was super lucky as so much of it had bled off that it felt more like a slap that left me all tingly for hours.

Same here! I still love watching it but that moment sent me inside and has definitely made me realize it's better to get inside in some instances!

This article describes ("corona discharge") what is the prelude to what you are describing ("upward streamer".)

The article said "nearly invisible to the naked eye" (emphasis mine). Between that and the fact the researchers weren't that close to an actual lightning strike (meaning you presumably would have seen a stronger effect), I would believe you saw something.

You saw it, the human visual response curve is horribly uneven between individuals. Some can see fairly good into the UV range (especially those who have had cataract surgery,) while some can't even see 415nm violet but can see blue and red-mixed purple all day.

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...

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?

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

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.

When I worked in a lab that took videos with a UV camera, I still called them videos, and I would absolutely have said that I took a video of the subject (a methanol flame in this case).

Essentially every color photograph you have ever seen is a composite of a red photographic, a green photograph, and a blue photograph.

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.

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...

what's the job?

> (1:If you come to my day job), and (2: we shut off all the lights) (3:in the test room), (4:after your eyes adjust in the dark for a minute), you'll see the soft purple glow coming (5:from the edge our 160kV test rig).

So, 5 different things that make it glow "not coming from treetops". Parent poster wanted to see glowing treetops in a forest, where we might not be adjusted to dark for a minute.

You can also see such corona discharge with benchtop tesla coils even in lighted room, but those are not trees in forest glowing from a storm.

Even a smallish Tesla coil easily produces voltages north of 160kV. I built one using 4" PVC for the secondary with a wound length of maybe ~2 feet of secondary? From memory of the calculations I did at the time I think it was around 350 kV peak? Might have been higher. Threw 24 inch sparks quite easily.

I’m not saying it can’t be seen, I’m saying that you can’t prove something can be seen by showing me a photo that captures light that I can’t see.

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. :)

I suppose this also depends on the types of remote controls? There are some where I can see red and some where I cannot.

The faint red glow is actual red light as many IR LED's (esp the ones used in cameras for night illumination) are close to the visible spectrum and have some visible light emission.

850nm is easily visible, but most remotes are 940nm, which is also visible as a faint purple glow but the source needs to be really bright.

Isn't infrared, by definition, wavelengths beyond what people can see?

Which people? And no, it's not defined that way: "radiation having a wavelength between about 700 nanometers and 1 millimeter"

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.

Which photograph? The one in the article is not from the paper. The paper contains no photographs of corona.

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.)

> then perma black, I assume.

Probably not.

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

This was a very depressing read.

What he explains sounds exactly like what you (or at least I) see when you close your eyes and then put pressure on them.

The way I had it explained was trying to look out one eye while the other’s closed

While reading I thought this is basically visual tinnitus and then the author used exactly that term. As someone with tinnitus, I can definitely understand the longing for "absolute darkness".

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.

Lol.

At work, some guy has been pushing a 2-day feature into its 5th week now, with questions like "what do you mean by (database) table?" "Is <not_a_database_table> a database table?"

Etc...

We have to fill-in RFDs to answer those kind of questions, so the process is massively slow and st...(expunged due to HN guidelines).

So yeah, some people really love their semantics and are willing to do whatever it takes to keep it that way.

[You can take a guess at where this startup will be in 2-3 years ...]

wrong thread?

Sure, a photo taken in non-visible spectrum is still a photo. And stacking photos taken with different wavelength filters or sensor can also be considered a photo. For example the headline image of the spruce tips taken in a lab is photo. And based on the description of the UV camera in the paper, they did generate UV video of the tree tops.

However, the linked article and associated paper don't have any such photos (or video) of the corona in the treetops. Instead the UV video was processed with a detection algorithm, and then the visible-light photos and video were annotated with graphed dots of where detections were seen. Those dots aren't a photo of the corona by any reasonable definition.

Can you point me to the images of corona in the paper which I missed?

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

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".)

Half of the comments are in this subthread which derailed the discussion on this submission before it even started. Here the damage is done but maybe, please, refrain from doing so elsewhere.

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.

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.

Great time to read about St Elmo's Fire!

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

Sounds like a man in motion :)

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

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

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.

The lines about oxidizers cleaning the air reminds me of the aspects of late 1800's and early 1900's product marketing oversimplifying hygiene. Bleach everything, whether it needs it or not; anything that indiscriminately kills all bacteria can only make the world a better place!

To be fair with the lack of refrigeration and general spread of disease and vermin this could have been a great idea at the time

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

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

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.

> “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?

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.

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????

The images in the article are not from the paper. The paper contains no images of corona.

Reminds me of Hyperion Tesla trees.

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

made me giggle

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

Is there a hypothesised purpose? Do discharges from plants that evolved in biomes with frequent lightning strikes differ from those that evolved without them?

Will head hair on humans do this too?

Wouldn't we smell it if it did?

It's not very conductive, so it won't have any appreciable discharge, but the hairs will repel each other, which is easy to see. Search for "Van de Graaff generator" and "hair", to see lots of pictures.

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