Astronomy Picture of the Day - Northern Lights from the Stratosphere

NASA ^ | Image Credit & Copyright: Ralf Rohner

[MtnClimber]

Explanation: Northern lights shine in this night skyview from planet Earth's stratosphere, captured on January 15. The single, 5 second exposure was made with a hand-held camera on board an aircraft above Winnipeg, Canada. During the exposure, terrestrial lights below leave colorful trails along the direction of motion of the speeding aircraft. Above the more distant horizon, energetic particles accelerated along Earth's magnetic field at the planet's polar regions excite atomic oxygen to create the shimmering display of Aurora Borealis. The aurora's characteristic greenish hue is generated at altitudes of 100-300 kilometers and red at even higher altitudes and lower atmospheric densities. The luminous glow of faint stars along the plane of our Milky Way galaxy arcs through the night, while the Andromeda galaxy extends this northern skyview to extragalactic space. A diffuse hint of Andromeda, the closest large spiral to the Milky Way, can just be seen to the upper left.

[MtnClimber]

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For more detail go to the link and click on the image for a high definition image. You can then move the magnifying glass cursor then click to zoom in and click again to zoom out. When zoomed in you can scan by moving the side bars on the bottom and right side of the image.

[MtnClimber]

[MtnClimber]

Pinging the APOD list.

🪐 🌟 🌌 🍔

[sauropod]

Bkmk

[Paladin2]

Thanks for posting.

At least I get some good results from Fed. expenditures on occasion.

[Paladin2]

Why is the color different based on Altitude?

[gundog]

Stratification of the atmosphere? Composition and temp varying with altitude?

[No name given]

Just beautiful.

[metmom]

I love astronomy overall, but I think my favorite celestial events are auroras.

I’ve seen far fewer than I’d have liked to.

[verum ago]

Why is the color different based on Altitude?

Short answer: different light emitting oxygen species take different amounts of time to do so, and at lower altitudes the one that emits red can't survive long enough to emit a photon on its own before bumping into something else (atmosphere is denser the lower you get), which rob it of the energy needed to emit light.

Straight from the NOAA Space Weather Prediction Center's "Aurora Tutorial" page:

Different auroral colors come from different heights in the atmosphere primarily because the life-time of an excited atom or molecule (time spent in its excited state) is vastly different for different colors of the aurora. The green aurora from oxygen in the 1S state typically occurs from 120 to 400 km (80 to 250 miles) above the surface of Earth. The red aurora from oxygen in the 1D state is restricted to altitudes above 300 km (180 km). This is because oxygen in the 1D state has a very long lifetime (>150 sec) and can only survive in the thinner atmosphere above 300 km. At lower altitudes the oxygen in the 1D state collides with other atmospheric atoms or molecules before it can emit a photon which deactivates or quenches the excited oxygen. The 1S state of oxygen has a lifetime of about 1 second and therefore emits a photon more quickly and thus can emit at lower altitudes where the density is higher. The aurora sometimes has a purplish lower border which comes from emissions from molecular nitrogen. This "prompt" emission is emitted from excited states of nitrogen that have almost no delay between excitation and emission. It survives at even lower altitudes between 120 and 200 km (80 to 120 miles). In the video sequence at the end of this readme document, the purple emissions from the nitrogen seems to lead the green emissions from the oxygen. This is an example of the difference between the prompt emission of nitrogen vs the emission from the longer-lived excited state of oxygen.

I recommend visiting the page. It's a pretty good primer on the aurora.

[Paladin2]

Who knew?

Thanks.

[Pete from Shawnee Mission]

M.C. Love aurora pictures! Thanks for posting! Here is a Youtube Video of ISS views of the night side of Earth, some showing lightning flashes, some showing aurora. (Unfortunately it does not provide the music titles.

Video from ISS Set to music by Stellerdrone

I watch it now and then. Search Stellerdrone for other music.

[MtnClimber]

Very nice. I jumped ahead a lot. That is a long video! Over four hours!

[Pete from Shawnee Mission]

It is long. I also jump around and try to guess which continent they are passing over sometimes. (I might watch for 10 or 15 min at a sitting.)

YouTube also has some good videos with back ground white noise or brown noise that I can play while I do something else. (Rain on a Hanock roof in Korea, or Rain in Japanese Garden are good ones.)