APOD: A Glowing STEVE and the Milky Way (2020 Nov 17)

[APOD Robot]

A Glowing STEVE and the Milky Way

Explanation: What's creating these long glowing streaks in the sky? No one is sure. Known as Strong Thermal Emission Velocity Enhancements (STEVEs), these luminous light-purple sky ribbons may resemble regular auroras, but recent research reveals significant differences. A STEVE's great length and unusual colors, when measured precisely, indicate that it may be related to a subauroral ion drift (SAID), a supersonic river of hot atmospheric ions thought previously to be invisible. Some STEVEs are now also thought to be accompanied by green picket fence structures, a series of sky slats that can appear outside of the main auroral oval that does not involve much glowing nitrogen. The featured wide-angle composite image shows a STEVE in a dark sky above Childs Lake, Manitoba, Canada in 2017, crossing in front of the central band of our Milky Way Galaxy.

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[Guest]

I hate these curved galaxy photos. I wish you folks would t post them anymore.

[Chris Peterson]

I hate these curved galaxy photos. I wish you folks would t post them anymore.

This is a STEVE picture. It just happens to have the Milky Way in it... as almost any wide angle image of night sky will.

[Ann]

I hate these curved galaxy photos. I wish you folks would t post them anymore.

I like curved galaxy photos. I'm just a little less sure about aurora photos.

Oh, wait, this is not an aurora photo, it's STEVE photo... whatever. It's nice as long as I don't have to say anything smart about it. I'll let Steve speak for himself.

Oh, P.S., you knew I would say it, don't you? What's that blue smear at the very top of this image?

You know what it is, don't you? Say it! Say it!

Ann

So the "g" emoji didn't turn out the way I hoped, but today's APOD might help you decipher it...

[neufer]

<<A subauroral ion drift (SAID), also known as a polarisation jet, is an atmospheric phenomenon driven by substorms in the Earth’s magnetosphere. First discovered in 1971, a SAID is a latitudinally narrow (1-2° MLAT) layer of rapid, westward flowing ions in the Earth’s ionosphere. Though not traditionally associated with an optical emission, the STEVE discovery paper suggested the first link between this optical emission’s occurrence and that of an extremely fast and hot SAID event. SAIDs are observed equatorward of the auroral zone, at subauroral latitudes, typically in the local time sector between 18:00 hours and 22:00 hours. They can occur individually, or as multiple events. SAIDs are characterised by a reduced density of ions, a strong westward flow, and an increased temperature. They can last between 30 minutes and 3 hours. The exact characteristics of SAID events appear to have solar cycle, seasonal, and diurnal dependences.

Although studied for decades, prior to the formal discovery of STEVE, SAIDs had never been associated with an optical emission. STEVE was associated with a particularly extreme SAID, with a velocity over twice the norm and 100 K hotter. STEVE has presented a new way for scientists, including citizen scientists, to study SAIDs.

Animation of von Kármán vortex vortex street created by a cylindrical object; the flow on opposite sides of the object is given different colors, showing that the vortices are shed from alternating sides of the object

---

STEVE often, although not always, is observed above a green, "picket-fence" aurora. Although the picket-fence aurora is created through precipitation of electrons, they appear outside the auroral oval and so their formation is different from traditional aurora. The study also showed these phenomena appear in both hemispheres simultaneously. Sightings of picket-fence aurora have been made without observations of STEVE. The green emissions seem to be related to eddies in the supersonic flow of charged particles, similar to the eddies seen in a river, which move more slowly than the other water around them. The green bars in the picket fence are moving more slowly than the structures in the purple emissions, and some scientists have speculated they could be caused by turbulence in the charged particles from space.>>

[orin stepanek]

SteveMilkyWay_NasaTrinder_960.jpg

X marks the spot? ? I notice some of that so called picket fence
next to the Aurora!

[johnnydeep]

I hate these curved galaxy photos. I wish you folks would t post them anymore.

Click to play embedded YouTube video.

I like curved galaxy photos. I'm just a little less sure about aurora photos.

Oh, wait, this is not an aurora photo, it's STEVE photo... whatever. It's nice as long as I don't have to say anything smart about it. I'll let Steve speak for himself.

Oh, P.S., you knew I would say it, don't you? What's that blue smear at the very top of this image?

You know what it is, don't you? Say it! Say it!

Ann

So the "g" emoji didn't turn out the way I hoped, but today's APOD might help you decipher it...

I guessed the blue smear was Vega before deciphering your emoji-rebus solely based on your prior posts. Then I realized the meaning of the emojis: Van, Earth, Starry Sky?, Apple. Interestingly, I only see the galaxy emoji in the editing view of this post, and it transforms into a Starry Sky emoji after posting as you apparently also saw.

So, if Vega is the blue star toward the middle top, what's the blue star smear toward the top right?

Also, that little STEVE video was surprisingly pleasing. Still not sure what it's really about though

[Ann]

I hate these curved galaxy photos. I wish you folks would t post them anymore.

Click to play embedded YouTube video.

I like curved galaxy photos. I'm just a little less sure about aurora photos.

Oh, wait, this is not an aurora photo, it's STEVE photo... whatever. It's nice as long as I don't have to say anything smart about it. I'll let Steve speak for himself.

Oh, P.S., you knew I would say it, don't you? What's that blue smear at the very top of this image?

You know what it is, don't you? Say it! Say it!

Ann

So the "g" emoji didn't turn out the way I hoped, but today's APOD might help you decipher it...

I guessed the blue smear was Vega before deciphering your emoji-rebus solely based on your prior posts. Then I realized the meaning of the emojis: Van, Earth, Starry Sky?, Apple. Interestingly, I only see the galaxy emoji in the editing view of this post, and it transforms into a Starry Sky emoji after posting as you apparently also saw.

So, if Vega is the blue star toward the middle top, what's the blue star smear toward the left right?

Also, that little STEVE video was surprisingly pleasing. Still not sure what it's really about though

My goodness, Johnny, that's Vega!!!!

Cygnus and Lyra.png

Take a look at my cropped and clumsily annotated version of today's APOD. At left is the outline of Cygnus. The blue star at top is Delta Cygni, which, coincidentally, is pretty much exactly the same color as Vega. Lyra, on the other hand is at right, and Vega is the bright star at far right!!!

As for my emoji-rebus, the one that looks like a starry sky looked like a galaxy when I found it at https://getemoji.com! So my rebus should read, Van, Earth, Galaxy, Apple.

Thanks for setting me straight!

P.S. I, too, thought the little Steve video was kind of funny. And it's less then two minutes long, too. "Hi, I'm Steve - just kidding, my name isn't Steve..." I thought that was appropriate for today's STEVE APOD!

Ann