The story of Steve, the mysterious pink-ribbon aurora, shows how citizen scientists are making important contributions to research and discovery.

Steve, the friendly neighborhood aurora
To the naked eye, Steve is a faint, pink ribbon across the sky. (Click for larger image.)
Chris Ratzlaff

For years aurora chasers have seen something unknown in the sky. Equatorward from the primary aurora (that is, south of the Aurora Borealis, north of the Aurora Australis), this seemingly rare phenomenon appears as a thin, pink ribbon, sometimes quite dim, and at lower latitudes than researchers normally investigate.

Searching through research papers, the aurora chaser community concluded that this phenomenon was a “proton arc.” Just as electrons raining down on Earth’s atmosphere create aurora, protons should generate similar light displays. As the community grew, reports of these “proton arcs” expanded as well — over the last two years, members of the Alberta Aurora Chasers Facebook group (nearing 10,000 members world-wide) logged quite regular sightings. What had initially seemed rare turned out to be a common phenomenon once we started paying attention.

Introducing Steve

In early 2016 the Alberta Aurora Chasers began forming a relationship with the Aurorasaurus citizen-science project, aiding in the effort to gather real-time data about aurora sightings. When Aurorasaurus founder Liz MacDonald (NASA Goddard) came to speak with our community, she introduced us to Eric Donovan (University of Calgary, Canada). While socializing afterward, one of our members, Neil Zeller, showed Donovan his photo of a “proton arc.”

To our surprise, Donovan explained that actual proton arcs look quite different and, more importantly, aren’t visible to the naked eye — and he didn’t know what our thin, pink ribbon was. Due to our experience at photographing the ribbon of light, Donovan proposed working with us to learn more about it.

Steve's pink-ribbon aurora
The pink ribbon crosses the sky equatorward of more typical aurora.
Catalin Tapardel

There was, however, a catch. Donovan implored upon us to stop calling it a “proton arc;” the name was already taken and implied that the ribbon came from protons raining down on Earth’s atmosphere, which didn’t seem to be the right explanation. He also suggested that a “sciency sounding name” wouldn’t do, since we didn’t yet understand the processes that created it. So, I suggested something not sciency at all: Steve.

As part of our collaboration, Donovan pored through astrophotographers’ images until he identified an event that had also been observed from the sky: One of the European Space Agency’s three Swarm satellites, which collect information on electric and magnetic fields in Earth’s upper atmosphere, flew right through a ribbon. Photos from Alberta Aurora Chaser member Song Despins visually confirmed that the ribbon Swarm observed was indeed Steve.

Understanding Steve

Swarm spacecraft
This artist's impression shows the true design of the European Space Agency's three Swarm spacecraft.
ESA / AOES Medialab

From the Swarm data, we now know that Steve occurs equatorward from the primary aurora at an altitude of about 300 km (180 miles, in the ionosphere), at a toasty temperature of 3,000°C. The 25-km-wide ribbon stretches from the eastern to the western horizon.

Steve often appears faint to the naked eye and can be photographed with similar settings used for aurora (5- to15-second exposures, ISO 800-3200, aperture as low as your lens supports). While what causes Steve remains an enigma, as a community, we've gotten really good at catching him on camera. Our aurora-researching friends at Aurorasaurus and the University of Calgary have challenged us to continue to gather data so they can learn more about Steve's origins.


Image of Tom-Reiland


May 15, 2017 at 4:26 pm

I observed a Ribbon Aurora at least 30 years ago at an observing site in Greene County, Pa. The ribbon started as two separate sections coming out of the East and West and meeting near the Zenith. It didn't last very long. I prefer to call it a Ribbon Aurora because it describes the appearance of the Aurora, just as Rays, Bands and Arcs are other types of Aurora.

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