Aurora, in the pink

By Phil Plait | June 18, 2012 6:30 am

’tis the season for solar storms, and I’m hearing reports that Active Region 1504 (the same sunspot featured in a dramatic video I posted recently) has been getting feisty, blowing out some flares and causing auroral activity here on Earth.

Photographer Brad Goldpaint was in the right place at the right time Saturday night to see some of this: he went to Crater Lake, Oregon, and at 3:30 a.m. local time on June 17th he took this surpassingly beautiful picture of a somewhat rare event: pink aurorae!

[Click to recombinate.]

Gorgeous! And weird. The colors you see in aurorae depend mostly on what’s in the air. Literally! A solar storm is an eruption of subatomic particles launched from the Sun at high speed. These interact with the Earth’s magnetic field, which, through a complicated process, sends those little beasties down into our air. They slam into the molecules and atoms in the upper atmosphere, blasting off electrons like bullets hitting concrete and sending out shrapnel.

When electrons recombine with the atoms and molecules, a little bit of energy is released in the form of light, and the color of that light depends on what’s doing the emitting. Oxygen atoms, for example, tend to glow green and/or red. Oxygen molecules (two atoms combined, like the kind we breathe) glow blue. Nitrogen molecules can glow either red or blue. Here’s a diagram from the excellent Atmospheric Optics website:

As you can see, several colors are emitted by the various atoms and molecules. One color you won’t see there, though, is pink. That’s because pink isn’t a spectral color; that is, part of the ROYGBIV red-orange-yellow-green-blue-indigo-violet spectrum.

If you have a source of red and blue light, these can combine to make something look magenta or pink, like in the diagram here. I strongly suspect that’s what’s going on here; we’re seeing a combination of red and blue light emitted by nitrogen molecules high over the Earth, and our eyes see that balance as pink. Cameras are designed to see colors much the way our eyes do, so the aurora looks pink in pictures as well.

Pink aurorae aren’t unknown, but it is rare to see the color this strongly with no almost no other coloring at all. And of course, Brad’s photographic skills are excellent, so it’s not just the color but the scene itself in his photo that is so breathtaking. He has another shot he took that night, too. Crater Lake is one of my favorite places on Earth, and if you’ve never been, go! If you time it well, you may be mesmerized not just by the Earth below, but by the heavens above as well.

Image credits: Brad Goldpaint (used by permission); Atmospheric Optics; Wikipedia

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Comments (14)

  1. Nigel Depledge

    That sure is a stunning photo.

    And magenta aurora too!

  2. Daniel J. Andrews

    My 3D sun app has been sending me notices about these storms, but we’ve been having thick cloud up here in the far north. Annoying, as I’m fairly far north right now and would have spectacular views if it would just stop raining.

  3. Bob Olsen

    I have seen some purple pink in auroras up in Northern Alberta, but never like that, I did watch that red aurora last year which was incredible, wish I could have gotten some pics but unfortunately my camera battery was dead

  4. Matt B.

    You know, chemists should really come up with names to differentiate atoms from molecules made of those atoms. “Hydrogen”, “oxygen” and “nitrogen” are often used confusingly.

    Funny, that color Venn diagram looks a lot like some diagrams I made for linguistics on LiveJournal.

  5. It’s going back a long time for me, but I believe our perception of pink is essentially “!green” much like white is the perception when we see all colours mixed, pink is “all colours except green”

  6. Electro

    Bob Olsen,
    Of the zillions of aurorae I have watched from Ft McMurray, I remember one from the mid eighties that was a brilliant pink, blue and green in defined bands with very active motion patterns.
    Many folks in town were talking about it the next day but I have never seen anything even approaching it since.
    It also seemed unusual to me for being directly overhead rather than on the horizons, and for the amount of sky it covered.

  7. NeilNZ

    Video and still pictures of Aurora Australis display in New Zealand.

  8. Marina Stern

    I’m jealous. I’m hundreds of miles north of Crater Lake, but socked in with heavy cloud cover. The best I’ve gotten was a faint red glow on the northern horizon, following a solar storm last year.

  9. Kumar

    On a somewhat different note, Goldpaint is an AWESOME name for a photographer.

  10. r.

    i love the purple pinkness of it!

  11. Thanks for that informative link, Dr. Plait! I’d always wondered how exactly aurora can display those different colors. I mean, I’d heard that oxygen and nitrogen produce different colors, but I never understood why they didn’t all simply blend together. I never found an explanation of aurora that actually explained that.

    Oh yeah, pretty picture too :)


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