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Ultraviolet corona discharges on treetops during storms

psu.edu

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Re: Ultraviolet corona discharges on treetops during storms

#21

Post by chrisfosterelli »

addaon wrote: post #10
colanderman wrote: post #3

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…

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?

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.

Re: Ultraviolet corona discharges on treetops during storms

#22

Post by WarmWash »

clickety_clack wrote: post #20
addaon wrote: post #10

Earlier quoted context omitted.

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?

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...

Re: Ultraviolet corona discharges on treetops during storms

#23

Post by ajkjk »

WarmWash wrote: post #22
clickety_clack wrote: post #20

Earlier quoted context omitted.

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.wikimed…

what's the job?

Re: Ultraviolet corona discharges on treetops during storms

#24

Post by antimora »

> “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?

Re: Ultraviolet corona discharges on treetops during storms

#25

Post by chankstein38 »

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?

Re: Ultraviolet corona discharges on treetops during storms

#26

Post by yetihehe »

WarmWash wrote: post #22
clickety_clack wrote: post #20

Earlier quoted context omitted.

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.wikimed…

> (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.

Re: Ultraviolet corona discharges on treetops during storms

#27

Post by raincole »

colanderman wrote: post #3

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…

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.)

Re: Ultraviolet corona discharges on treetops during storms

#28

Post by latexr »

raincole wrote: post #27
colanderman wrote: post #3

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…

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

Re: Ultraviolet corona discharges on treetops during storms

#29

Post by stronglikedan »

chankstein38 wrote: post #25

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 e…

> 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.

Re: Ultraviolet corona discharges on treetops during storms

#30

Post by ihsw »

chankstein38 wrote: post #25

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 e…

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