Scientists have claimed that the new kind of aurora – STEVE – that made headlines back in 2016 and subsequently every time it appeared, isn’t actually an aurora, but an entirely new celestial phenomenon.
STEVE appears as thin ribbons of purple and white light and has been captured on film for decades, but the scientific community only got wind of STEVE in 2016. When scientists first looked at images of STEVE, they realized the lights were slightly different than light from typical auroras but were not sure what underlying mechanism was causing them.
In a new study, researchers analyzed a STEVE event in March 2008 to see whether it was produced in a similar manner as the aurora, which happens when showers of charged rain down into Earth’s upper atmosphere. The study’s results suggest STEVE is produced by a different atmospheric process than the aurora, making it an entirely new type of optical phenomenon.
The study authors have dubbed STEVE a kind of “skyglow,” or glowing light in the night sky, that is distinct from the aurora. Studying STEVE can help scientists better understand the upper atmosphere and the processes generating light in the sky, according to the authors.
Scientists started using data from satellites and images from ground-based observatories to try to understand what was causing the unusual light streaks. The first scientific study published on STEVE found a stream of fast-moving ions and super-hot electrons passing through the ionosphere right where STEVE was observed. The researchers suspected these particles were connected to STEVE somehow but were unsure whether they were responsible for producing it.
After that first study researchers wanted to find out if STEVE’s light is produced by particles raining down into the ionosphere, as typically happens with the aurora, or by some other process. In the new study, scientists analyzed a STEVE event that happened over eastern Canada on March 28, 2008, using images from ground-based cameras that record auroras over North America. They coupled the images with data from NOAA’s Polar Orbiting Environmental Satellite 17 (POES-17), which happened to pass directly over the ground-based cameras during the STEVE event. The satellite is equipped with an instrument that can measure charged particles precipitating into the ionosphere.
The study’s results suggest STEVE is an entirely new phenomenon distinct from typical auroras. The POES-17 satellite detected no charged particles raining down to the ionosphere during the STEVE event, which means it is likely produced by an entirely different mechanism, according to the authors.
The researchers said STEVE is a new kind of optical phenomenon they call “skyglow.” Their next step is to see whether the streams of fast ions and hot electrons in the ionosphere are creating STEVE’s light, or if the light is produced higher up in the atmosphere.