STEVE, a strange ribbon of purple and green haze discovered by citizen scientists in 2016, just got weirder. While sifting through archival data, a team of scientists discovered that the aurora-like phenomenon has a secret twin that moves in the opposite direction.
A photo of STEVE’s long-lost sibling hanging out over the Norwegian Arctic was found in the archives of the all-sky digital camera at the Ramfjordmoen Research Station in Norway, according to a new study published in Earth, planets and space.
Strong improvement in thermal emission rate, also known as STEVE, was first spotted in photos on the Facebook group Aurora Chasers, appearing as unusual purple streaks in the night sky. The name STEVE was chosen in honor of the children’s film Over the hedge, in which a character randomly comes up with the name STEVE to describe an object he is unsure of. STEVE’s full name was later composed to fit the acronym.
Although it may appear around the same time as the Northern Lights, the different colors did not match the shades of green, blue and red normally seen in the aurorae. The aurorae also often last for hours, while STEVE graces the sky for a short time.
Scientists were naturally intrigued, so they began investigating the strange aurora-like phenomenon. On closer inspection, STEVE was categorized as a fast-moving stream of extremely hot gas, a so-called sub-auroral ion drift.
Auroras are created by the solar wind hurling particles toward Earth, which are then guided to the north and south poles by the planet’s magnetic field. The particles collide with atoms and molecules in the upper atmosphere, resulting in the shimmering green light that takes over the night sky.
STEVE is triggered by the same process, but travels along different magnetic field lines. As a result, it can occur at much lower latitudes. STEVE’s strangeness doesn’t end there, though. The aurora-like phenomenon occurs at dusk, when the flow of hot gas moves westward. Scientists have always wondered if STEVE could have an eastward-moving twin brother who would appear at dawn.
That’s when an international team of researchers combed through archival data and, with the help of citizen scientists, sifted through images of auroras captured by the Ramfjordmoen Research Station’s digital camera. Similar to the discovery of STEVE himself, it was citizen scientist Gabriel Arne Hofstra who found a STEVE look-alike in a photo taken on December 28, 2021.
“It was great to have contributed to new science and helped scientists discover this phenomenon,” Hofstra said in an email rack. “To me it proves that we citizens can contribute to understanding the world we live in by working together with scientists.”
STEVE’s twin formed an arc that stretched more than 600 miles, appearing just after midnight on the polar side of the green aurora also seen in the image.
Aside from their physical similarities, the European Space Agency (ESA) also used its trio of Swarm satellites to collect magnetic field data during the time the image of STEVE’s twin brother was captured. Although none of the satellites flew directly through the arc at the same time and place as observed in the all-sky image, two of them did measure conditions in the purple region before, during and after the event. From the data, scientists were able to trace an easterly ion flow in the purple region.
As we continue to gaze into the night sky, phenomena like STEVE remind us that there is always more to discover than what is visible. With each new find, scientists and citizen observers alike bring us closer to unraveling the mysteries of our amazing planet.
More: 25 mesmerizing photos of the Northern Lights