APOD: Meeting in the Mesosphere (2020 Jul 04)

Comments and questions about the APOD on the main view screen.
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APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by APOD Robot » Sat Jul 04, 2020 4:05 am

Image Meeting in the Mesosphere

Explanation: A sensitive video camera on a summit of the Vosges mountains in France captured these surprising fireworks above a distant horizon on June 26. Generated over intense thunderstorms, this one about 260 kilometers away, the brief and mysterious flashes have come to be known as red sprites. The transient luminous events are caused by electrical breakdown at altitudes of 50 to 100 kilometers. That puts them in the mesophere, the coldest layer of planet Earth's atmosphere. The glow beneath the sprites is from more familiar lighting though, below the storm clouds. But on the right, the video frames have captured another summertime apparition from the mesophere. The silvery veins of light are polar mesospheric clouds. Also known as noctilucent or night shining clouds, the icy clouds still reflect the sunlight when the Sun is below the horizon.

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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by A vent » Sat Jul 04, 2020 6:25 am

Welcome to the window to what we simians normally cannot see. Bioluminescent squid and hotspots on Jovian moons are wonderful

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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by Ann » Sat Jul 04, 2020 6:57 am

Two great videos to watch here:

Click to play embedded YouTube video.
Click to play embedded YouTube video.



















The first video (from NASA) focuses on blue jets, yay! The other one, made by amateurs, explains a lot about red sprites (mostly) and some of the blue phenomena involved. I find both of them great.

And I think that the picture at right is a superb image of the high-altitude, glowing-in-the-night noctilucent clouds! :D

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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by JohnD » Sat Jul 04, 2020 10:27 am

Thank you, Ann, for those vidoes! I found the second from the lightning chasers especially 'exciting'!

But I'm sorry. On my screen I could not see a trace of green! Ann, as Colour Queen, can you support an alternative explanation, that of an effect in colour vision, an after-image? The observers, with wide, dark-adapted eyes, receive an intense red image, which saturates the red cone receptors in their retina. For a few moments, the imbalance in signalling to the brain causes a green after-image. The effect doesn't occur in light adapted eyes, watching a low intensity screen, because too little light reaches the retina to saturate the red receptors.

Try this experiment. Hold something very red under a desk lamp, so that it is intensely illuminated. Stare at it for half a minute, the close your eyes. I see a brief, green after-image.

And another Q, one for Chris maybe! Oxygen concentration at very high altitude. All I can find applies to flying height, deals with respiratory consequnces of altitude, and assumes that the relative concentration of oxygen and nitrogen remains constant. Why/how does diffusion mixing fail at the height of hundreds of kilometers, so that the concentration of oxygen rises?

John

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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by orin stepanek » Sat Jul 04, 2020 11:45 am

msv1000crop.jpg

Would have been nice to be in France on my B-Day! :mrgreen: So I could have
had Mesosphere fireworks to help me celebrate! 8-)
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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by Ann » Sat Jul 04, 2020 12:55 pm

orin stepanek wrote:
Sat Jul 04, 2020 11:45 am
msv1000crop.jpg


Would have been nice to be in France on my B-Day! :mrgreen: So I could have
had Mesosphere fireworks to help me celebrate! 8-)

Is it your birthday, Orin?

Congratulations! :D

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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by Ann » Sat Jul 04, 2020 12:58 pm

JohnD wrote:
Sat Jul 04, 2020 10:27 am
Thank you, Ann, for those vidoes! I found the second from the lightning chasers especially 'exciting'!

But I'm sorry. On my screen I could not see a trace of green! Ann, as Colour Queen, can you support an alternative explanation, that of an effect in colour vision, an after-image? The observers, with wide, dark-adapted eyes, receive an intense red image, which saturates the red cone receptors in their retina. For a few moments, the imbalance in signalling to the brain causes a green after-image. The effect doesn't occur in light adapted eyes, watching a low intensity screen, because too little light reaches the retina to saturate the red receptors.

Try this experiment. Hold something very red under a desk lamp, so that it is intensely illuminated. Stare at it for half a minute, the close your eyes. I see a brief, green after-image.

And another Q, one for Chris maybe! Oxygen concentration at very high altitude. All I can find applies to flying height, deals with respiratory consequnces of altitude, and assumes that the relative concentration of oxygen and nitrogen remains constant. Why/how does diffusion mixing fail at the height of hundreds of kilometers, so that the concentration of oxygen rises?

John
You're right that we humans see an "after-image" of a complementary color if we have been exposed to a bright light of a certain color. i.e., we might see green when we close our eyes after seeing a bright flash of red. But I don't think a camera would "see green" under such circumstances.

Personally I did see a bit of green in that video, but it was very faint.

Ann
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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by johnnydeep » Sat Jul 04, 2020 2:23 pm

Ann wrote:
Sat Jul 04, 2020 6:57 am
Two great videos to watch here:

Click to play embedded YouTube video.
Click to play embedded YouTube video.



















The first video (from NASA) focuses on blue jets, yay! The other one, made by amateurs, explains a lot about red sprites (mostly) and some of the blue phenomena involved. I find both of them great.

Ann
Thanks for the videos! The second one made clear a question I had about the APOD image. Namely, whether all those "sprites" appeared simultaneously (which I thought would be unlikely) or whether the image was a superposition of multiple images of separate "sprite" flashes. Your second video says the sprites come in clusters, and a cluster that looks VERY much like the one in the APOD image appears at 1:00.
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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by orin stepanek » Sat Jul 04, 2020 5:34 pm

Ann wrote:
Sat Jul 04, 2020 12:55 pm

Would have been nice to be in France on my B-Day! :mrgreen: So I could have
had Mesosphere fireworks to help me celebrate! 8-)

Is it your birthday, Orin?

Congratulations! :D

Ann
[/quote]













Actually; it was on the 26th; the day that the Mesosphere lightning show happened in France!😁
Orin

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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by Ann » Sun Jul 05, 2020 4:41 am

JohnD wrote:
Sat Jul 04, 2020 10:27 am
Thank you, Ann, for those vidoes! I found the second from the lightning chasers especially 'exciting'!

But I'm sorry. On my screen I could not see a trace of green! Ann, as Colour Queen, can you support an alternative explanation, that of an effect in colour vision, an after-image? The observers, with wide, dark-adapted eyes, receive an intense red image, which saturates the red cone receptors in their retina. For a few moments, the imbalance in signalling to the brain causes a green after-image. The effect doesn't occur in light adapted eyes, watching a low intensity screen, because too little light reaches the retina to saturate the red receptors.

Try this experiment. Hold something very red under a desk lamp, so that it is intensely illuminated. Stare at it for half a minute, the close your eyes. I see a brief, green after-image.

John
Red sprites blue jets green afterglow.png
John, can you see a little bit of green near my wiggly arrow?

I think the green stuff is some sort of "afterglow" that (sometimes) lasts longer than the red stuff.

Ann
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Re: APOD: Meeting in the Mesosphere (2020 Jul 04)

Post by JohnD » Sun Jul 05, 2020 9:14 am

Thank you, Ann! Yes, when blown up to full screen, there IS a little patch, haf the size of your arrowhead, that is greenish!

The theory proposed by the sprite chasers, that very intense sprites ionise oxygen, seems reasonable. But one would expect that above the more intense sprites on the right, not the lesser ones on the left.

I tried the after-image experiment on your picture, and could not get a green glow, but maybe the screen image is not intense enough.
John