Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Ultraviolet corona discharges on treetops during storms

psu.edu

Post reply on HN
Print view View original

11–20 of 69 posts

Re: Ultraviolet corona discharges on treetops during storms

#11

Post by arrowleaf »

colanderman wrote: post #4
mlhpdx wrote: post #2

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.

[flagged]

Human eyes can be sensitive down to 380nm, the UV range goes up to 400nm. Birds and insects can see this. We can see this, using UV filters such as shown in the article. I get that it's fun to be a pedant sometimes, but come on.

Re: Ultraviolet corona discharges on treetops during storms

#13

Post by t-3 »

mlhpdx wrote: post #2

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.

Re: Ultraviolet corona discharges on treetops during storms

#16

Post by none2585 »

dreamlayers wrote: post #14

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)

Re: Ultraviolet corona discharges on treetops during storms

#17

Post by GolfPopper »

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.

Re: Ultraviolet corona discharges on treetops during storms

#18

Post by adammarples »

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?

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

Re: Ultraviolet corona discharges on treetops during storms

#20

Post by clickety_clack »

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?

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.
Post reply on HN