Mystery of Purple Lights in Sky Solved With Help From Citizen Scientists

STEVE and the Milky Way at Childs Lake, Manitoba, Canada. The picture is a composite of 11 images stitched together. Credit: Courtesy of Krista Trinder

Notanee Bourassa knew that what he was seeing in the night sky was not normal. Bourassa, an IT technician in Regina, Canada, trekked outside of his home on July 25, 2016, around midnight with his two younger children to show them a beautiful moving light display in the sky — an aurora borealis. He often sky gazes until the early hours of the morning to photograph the aurora with his Nikon camera, but this was his first expedition with his children. When a thin purple ribbon of light appeared and starting glowing, Bourassa immediately snapped pictures until the light particles disappeared 20 minutes later. Having watched the northern lights for almost 30 years since he was a teenager, he knew this wasn’t an aurora. It was something else.

From 2015 to 2016, citizen scientists — people like Bourassa who are excited about a science field but don’t necessarily have a formal educational background — shared 30 reports of these mysterious lights in online forums and with a team of scientists that run a project called Aurorasaurus. The citizen science project, funded by NASA and the National Science Foundation, tracks the aurora borealis through user-submitted reports and tweets.

For the first time, scientists have ground and satellite views of STEVE (short for Strong Thermal Emission Velocity Enhancement), a thin purple ribbon of light. Scientists have now learned, despite its ordinary name, that STEVE may be an extraordinary puzzle piece in painting a better picture of how Earth’s magnetic fields function and interact with charged particles in space.

Credits: NASA’s Goddard Space Flight Center/Genna Duberstein

Download this video in HD formats from NASA Goddard’s Scientific Visualization Studio

The Aurorasaurus team, led by Liz MacDonald, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, conferred to determine the identity of this mysterious phenomenon. MacDonald and her colleague Eric Donovan at the University of Calgary in Canada talked with the main contributors of these images, amateur photographers in a Facebook group called Alberta Aurora Chasers, which included Bourassa and lead administrator Chris Ratzlaff. Ratzlaff gave the phenomenon a fun, new name, Steve, and it stuck.

But people still didn’t know what it was.

Scientists’ understanding of Steve changed that night Bourassa snapped his pictures. Bourassa wasn’t the only one observing Steve. Ground-based cameras called all-sky cameras, run by the University of Calgary and University of California, Berkeley, took pictures of large areas of the sky and captured Steve and the auroral display far to the north. From space, ESA’s (the European Space Agency) Swarm satellite just happened to be passing over the exact area at the same time and documented Steve.

NASA Needs Your Help to Find Steve and Here’s How

If you live in an area where you may see STEVE or an aurora, submit your pictures and reports to Aurorasaurus through or the free iOS and Android mobile apps. To learn how to spot STEVE, click here.

For the first time, scientists had ground and satellite views of Steve. Scientists have now learned, despite its ordinary name, that Steve may be an extraordinary puzzle piece in painting a better picture of how Earth’s magnetic fields function and interact with charged particles in space. The findings are published in a study released today in Science Advances.

“This is a light display that we can observe over thousands of kilometers from the ground,” said MacDonald. “It corresponds to something happening way out in space. Gathering more data points on STEVE will help us understand more about its behavior and its influence on space weather.”

The study highlights one key quality of Steve: Steve is not a normal aurora. Auroras occur globally in an oval shape, last hours and appear primarily in greens, blues and reds. Citizen science reports showed Steve is purple with a green picket fence structure that waves. It is a line with a beginning and end. People have observed Steve for 20 minutes to 1 hour before it disappears.

If anything, auroras and Steve are different flavors of an ice cream, said MacDonald. They are both created in generally the same way: Charged particles from the Sun interact with Earth’s magnetic field lines.

The uniqueness of Steve is in the details. While Steve goes through the same large-scale creation process as an aurora, it travels along different magnetic field lines than the aurora. All-sky cameras showed that Steve appears at much lower latitudes. That means the charged particles that create Steve connect to magnetic field lines that are closer to Earth’s equator, hence why Steve is often seen in southern Canada.

Specifically, the aurora and STEVE creation process starts with the Sun sending a surge of its charged particles toward Earth. This surge applies pressure on Earth’s magnetic field, which sends the Sun’s charged particles to the far side of Earth, where it is nighttime. On this far, night side of Earth, Earth’s magnet field forms a distinctive tail. When the tail stretches and elongates, it forces oppositely directed magnetic fields close together that join in an explosive process called magnetic reconnection. Like a stretched rubber band suddenly breaking, these magnetic field lines then snap back toward Earth, carrying charged particles along for the ride. These charged particles slam into the upper atmosphere, causing it to glow and generating the light we see as the aurora — and now possibly STEVE.
Credits: NASA Goddard’s Conceptual Image Lab/Krystofer Kim

Perhaps the biggest surprise about Steve appeared in the satellite data. The data showed that Steve comprises a fast moving stream of extremely hot particles called a sub auroral ion drift, or SAID. Scientists have studied SAIDs since the 1970s but never knew there was an accompanying visual effect. The Swarm satellite recorded information on the charged particles’ speeds and temperatures, but does not have an imager aboard.

“People have studied a lot of SAIDs, but we never knew it had a visible light. Now our cameras are sensitive enough to pick it up and people’s eyes and intellect were critical in noticing its importance,” said Donovan, a co-author of the study. Donovan led the all-sky camera network and his Calgary colleagues lead the electric field instruments on the Swarm satellite.

Steve is an important discovery because of its location in the sub auroral zone, an area of lower latitude than where most auroras appear that is not well researched. For one, with this discovery, scientists now know there are unknown chemical processes taking place in the sub auroral zone that can lead to this light emission.

Second, Steve consistently appears in the presence of auroras, which usually occur at a higher latitude area called the auroral zone. That means there is something happening in near-Earth space that leads to both an aurora and Steve. Steve might be the only visual clue that exists to show a chemical or physical connection between the higher latitude auroral zone and lower latitude sub auroral zone, said MacDonald.

“Steve can help us understand how the chemical and physical processes in Earth’s upper atmosphere can sometimes have local noticeable effects in lower parts of Earth’s atmosphere,” said MacDonald. “This provides good insight on how Earth’s system works as a whole.”

The team can learn a lot about Steve with additional ground and satellite reports, but recording Steve from the ground and space simultaneously is a rare occurrence. Each Swarm satellite orbits Earth every 90 minutes and Steve only lasts up to an hour in a specific area. If the satellite misses Steve as it circles Earth, Steve will probably be gone by the time that same satellite crosses the spot again.

In the end, capturing Steve becomes a game of perseverance and probability.

“It is my hope that with our timely reporting of sightings, researchers can study the data so we can together unravel the mystery of Steve’s origin, creation, physics and sporadic nature,” said Bourassa. “This is exciting because the more I learn about it, the more questions I have.”

As for the name “Steve” given by the citizen scientists? The team is keeping it as an homage to its initial name and discoverers. But now it is STEVE, short for Strong Thermal Emission Velocity Enhancement.


30 thoughts on “Mystery of Purple Lights in Sky Solved With Help From Citizen Scientists

    • Very true, Gerald, but some folks seem to think they know everything there is to know about it.

  1. Unfortunately, when I looked outside last night for a sight of an aurora, all I saw was rain and lots of it.

  2. I know that this is a naive question so I wont take umbrage if my ignorance is publicly exposed , but : is the solar system electrically charged neutral wrt the Galaxy and/or rest of the Universe.
    There are posts about the influence or noninfluence on climate from charged particle bombardment from the sun or as cosmic rays , which means that surely somewhere there is a source that is oppositely charged In the case of ions or electrons from the sun , what mechanism keeps the sun electrically neutral? If it is neutral that is.
    I am assuming that at the Big Bang the Universe thus created was electrically neutral with equal numbers of electrons and protons .

      • Darn.

        It’s hard to keep electrons and protons apart. Absent protons, it’s hard to keep large numbers of electrons together. Absent electrons, it’s hard to keep large numbers of protons together.

        You can take advantage of same charge repulsion with a coulomb explosion.

        Having said the above, the sun has a net charge but it’s actually rather small given its mass, “about 1 electron per million tons of matter.” link

    • I suspect if the solar system were to drift too far from electrical neutrality with respect to the rest of the galaxy, we’d see like charges being repelled and unlike charges being attracted until the imbalance was corrected.

      • I suspect you are correct, but any particles trying to work their way into the solar system from interstellar space would have to their way against the solar wind.

      • Well, this is going to depend on where you draw the boundary of the solar system. There is a whole lot of interstellar gas out there, and charged particles going every which way. The solar system undoubtedly has some net charge however you draw the boundary, but it will also likely not be significant relative the mass of the sun and probably vary over time.

  3. My night sky/aurora chasing buddy is named Steve and it upsets me (And him) that some “official’s” nomenclature has overridden all the various names that global observers have already coined!

    I was blown away when I witnessed “Tiger Stripes” and a “Proton Arc” alone one night, above my home in Tasmania.

  4. I saw a special on the meteor that hit Chelyabinsk, Russia in 2013. A lot of citizen science was gathered on this too. Cell phone cameras have at least on really great use—documenting phenomena that is rare and therefore hard to study using conventional methods. While some video and shots are very low resolution, some are quite good. So keep it up! Snap those photos!

  5. Watching the animated gif of the charged particles traveling towards the poles of the earth made me wonder if they have some kind of affect on the ozone hole.

    Just a thought…

  6. “The team can learn a lot about Steve with additional ground and satellite reports,”

    Or they could just ask me :)

    I am honoured to have an auroral phenomenon named after me!

  7. The paper says that the purple color is as yet unexplained, my understanding is that a purple color is often due to nitrogen, it’ll be interesting to see how that pans out.

  8. Somehow this phenomena will be tied to something awful that humans have or are doing and therefore we must grovel and apologize and give up our standard of living to make amends.

  9. I find it interesting that citizen scientists are encouraged to study atmospheric phenomena of an extraterrestrial origin, as this article describes (and I’d include astronomy as well as many of the hard sciences). But when it comes to CAGW, any citizen scientist from outside the cabal offering inconveniently conflicting observations is treated with scorn.

    Just sayin’…

  10. Gorgeous photo! I theorize that this is caused by the man made component of the CO2 in our atmosphere —and this goes to show that it’s worse than we thought. Soon, children will not know what a normal aurora looks like.

  11. “Leif Svalgaard, please pick up the white courtesy telephone. Leif Svalgaard.”

    The Safire Project just put out a video update of its progress.

    Since you have expertise in plasma dynamics, it would be interesting to hear your feedback.

  12. Deniers! We know everything we need to know. The science is settled, there is no possibility of new knowledge.

  13. Although I have not done any work in the field of aurora in several decades I feel I should comment to this post. First to the question raised by mikewaite. Practically speaking the solar system needs to be close to neutrally charged to avoid it blowing up since the forces resulting from a small imbalance in charge easily overrides the gravitational forces. However, some local small scale imbalances do occur in a plasma all the time also on earth. One of many examples is in the equatorial electro jet where a plasma is forced to move across the magnetic field resulting in a separation of charges (dynamo effect) and thus an electric field and usually an electric current. The details of this plasma physics is quite complicated, but the effect is seen all over the place as for instance in auroral displays.

    The colour of the aurora are caused by a whole bunch of different wavelengths but a few very dominant ones as eg 5577Å and 6300Å (I guess this dates me). Some of these wavelengths come from atoms and some from molecules, and since the atmosphere changes from being dominated by molecules to atoms as you get higher up you get a change in colour, the red colour being emitted from molecules lower down and the green from higher up. You see it in all kinds of auroral displays, it is best observed in rays that are usually green, but sometimes the lower edge is red. Most of the aurora you notice is green (5577Å) but sometimes you see strong red ones with very little green in it.

    The reason for the change in colour is a follows very superficial. High energy ionized particles (primary particles) are coming down along the magnetic field lines colliding with the particles in the atmosphere an exciting them. These particles will then emit light of a wavelength determined by the type of particle (spectroscopy). If the primary particles are soft (moderate energy – velocity) they will give off their energy high up in the atmosphere causing green aurora. If the primary particle is hard (higher energy) hey will make it to lower altitude before they give up all their energy and give raise to red aurora. So the color you notice in the aurora give an indication of energy of the primary particles, and a red auroral display tels you that the particles are hard.

    But my real reason for this comment has to do with how to observe the aurora. The most interesting details of the displays is observed in the magnetic zenith. This is up along the magnetic field lines usually south from overhead depending on your longitude. You can see the spiralling of the curls, the pulsations and if you are lucky you can observe the black aurora. If you really luck out and can record pulsating black aurora or black spirals you will have some data that has very seldom been recorded and never published (I think). Black aurora are black patches in a more or less uniformly diffuse aurora. THE AURORA IS NICE TO OBSERVE.

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