Chris Ratzlaff had been chasing the aurora borealis across Canada for about seven years when he met Steve. "Steve is predominantly pink-mauve in colour, quite a bit dimmer than the aurora overall. But the aurora is a big mass of green – Steve is always a very thin, almost like a delicate structure compared to the aurora, and it reaches from horizon to horizon, and is quite often fairly brief."
The glowing ribbon of purplish light that Chris describes is a "narrow, subauroral, visible structure, distinct from the traditional auroral oval" that, until this week, had yet to be formally recognised. Until a year ago it was largely undocumented in scientific literature and little was known about its formation. Now, with the help of citizen scientists, we have Steve.
"Steve is the visible counterpart to a feature in the upper atmosphere called a subauroral ion drift (SAID)," says Dr Elizabeth Macdonald, a geo- and heliophysicist at Nasa. Auroras occur when solar wind – a stream of charged electrons and protons flowing from the Sun – interacts with the Earth's magnetic field, generating strong electrical currents. Steve sits about 200km up in the atmosphere and is comparatively hot at 6,000°C, which may explain its colour. Scientists hope Steve will shed some light on the dynamics and structure of the Earth's magnetic field.
"We are just beginning to piece the mysteries of the significance of Steve together," Macdonald says. Steve's unusual colouring marked it out from more commons sightings of the aurora and its particular shape "occasionally indicated magnetic field-aligned substructures," according to a paper published on Wednesday, authored by Macdonald and a team of other scientists.
Ratzlaff moderates a Facebook group called the Alberta Aurora Chasers – an informal band of sky watchers or citizen scientists, now over 16,000-strong, which tracks the Northern Lights across their segment of Canada and shares photos of sightings. A few years ago, things began to get interesting when Ratzlaff and others in the group started collaborating with scientists and pooling their evidence in the National Science Foundation-funded Aurorasaurus database project, also led by Macdonald, which encourages amateur aurora lovers to upload their pictures. The special thing about this discovery is that it wouldn't have happened without their efforts – the same structure can in fact be seen from places including Michigan, Montana, Scotland and New Zealand.
Last April, in collaboration with the aurora chasers, Eric Donovan, a professor in physics and astronomy at the University of Calgary, presented a paper to the European Science Agency distinguishing the Steve-phenomenon by correlating with data collected by their Swarm satellite.
Why Steve? "When Eric wanted to start working with us, at the time we were inaccurately calling it a 'proton arc'," Ratzlaff says. They had taken the term from other communities who had also been spotting the formation for some time. "Eric said, 'you can't call it a proton arc because that name means something else entirely'. So he encouraged us to give it a placeholder name that didn't apply any physical properties… he didn't want us to bias the research." Steve now has its own backronym: Strong Thermal Emission Velocity Enhancement.
Ratzlaff says there are no special Steves in his life for whom the aurora was named. But "there's a scene in Over the Hedge, which is about a bunch of common filth animals, raccoons and squirrels and stuff, and they encounter this huge hedge and they don't know what it is – and it scares them, and one of the squirrels says, 'Let's call it Steve! It's a pretty name'."
This article was originally published by WIRED UK
