Usually observed at night in high latitudes, the Aurora has mesmerized skygazers and been the subject of numerous breathtaking photographs. They occur when charged plasma, driven by solar winds, gets ionized in the magnetosphere by the earth’s own magnetic field – resulting in a display of shimmering colors and wavy patterns. Throughout the past decade, however, photographers have managed to capture a slightly different display of light that almost resembles an Aurora. Unlike the Aurora’s broad, shimmering, horizontal bands of green, blue, or red – the unknown light appeared as a single ribbon of purplish-white color. It shoots vertically straight into the night sky – spanning more than an estimated 600 miles.
The magnificent, yet mysterious, display was named as “Steve”, a nod to the 2006 animated film Over the Hedge. At first, it was thought to be a ‘proton arc’, which occurs when protons hit the atmosphere as compared to Aurora’s electrons. However, scientists pointed out that proton arcs only diffuse visible light. Hence the name Steve stuck in the lingo of skygazers. To honor them for observing and documenting this phenomenon, scientists converted the name, Steve, into the “backronym” STEVE – Strong Thermal Emission Velocity Enhancement.
The backronym, really, was, based on satellite observations. In July 2016, the European Space Agency’s Swarm satellite, which measures Earth magnetic field, passed directly through STEVE. The on-board instruments confirmed the presence of an incredibly fast, ridiculously hot gas slicing through the atmosphere. The 16-mile wide band of gas was about 5,500 degrees Fahrenheit hotter than its surrounding and moved 500 times faster. Despite the observations, the mystery surrounding STEVE’s occurrence remained unknown – as was left to be considered a different kind of Aurora.
In 20th August, 2018, a new study published in the journal Geophysical Research Letters delved into the phenomenon first hand. The study captured images of STEVE from ground-based cameras and collected data from the National Oceanic and Atmospheric Administration’s Polar-orbiting Operational Environmental Satellites. The instruments onboard the satellite failed to detect any charged particles descending towards Earth’s magnetic-field lines, a relatively common observation for Aurora’s. Hence, they were able to put to bed the debate that STEVE is, definitely, not a form of Aurora.
Lead author of the study, Bea Gallardo-Lacourt, a space physicist at the University of Calgary in Alberta, Canada, has said, “Our main conclusion is that STEVE is not an aurora.” He added, “So right now, we know very little about it. And that’s the cool thing.” The researchers have dubbed the phenomenon a “sky glow”, and has mentioned that several observations at different levels of the atmosphere are required to uncover the mystery behind it.
One of the major reasons scientists became aware of this phenomenon is due to the efforts of a Facebook group called the Alberta Aurora Chasers. The Canada-based skygazers regularly coordinate to track and photograph the Northern lights in the country. It was a result of their photographs that STEVE managed to tickle the curiosity of scientists. Eric Donovan, a researcher at the University of Calgary in Canada, have pointed out that ten years ago, it would have cost $200 million to track the phenomenon over a course of 10 years. He said, “Today, with the help of citizen scientists and all the infrastructure that’s available for observation, it’s possible to close the loop in a matter of weeks.”