The STEVE phenomenon is not formed in the same way as the aurora; to understand

The phenomena known as STEVE, which consist of purple and green emissions into the atmosphere, could have their origin in the Earth’s magnetosphere, some 30,000 kilometers above the surface. A new study infers this after analyzing images of the same event taken in different locations by citizen scientists.

Although they sometimes consist of two green and purple bands, they both extend along the same magnetic field lines but at different altitudes. For the authors of the new research, there is no known mechanism in the ionosphere that can explain this phenomenon.

What are STEVE?

STEVE is the abbreviation for Strong Thermal Emission Velocity Enhancement – or “sharp increase in thermal emission velocity” in free translation – and manifests itself as a glow in the sky, with purple “streaks” accompanied by greenish vertical stripes with fences.

Discovered by amateur Canadian aurora watchers, the purple and green bands of light didn’t begin to be shared with scientists until 2016. faint and have different colors.

However, it is not yet clear exactly how or why these emissions form. Citizen scientists – ordinary people who contribute to professional scientists by providing data and images, for example – help researchers identify different types of STEVE.

Purple and green lights don’t always appear together, so the authors of the new study wanted to know if both colors were generated by the same event or phenomenon, but there was no easy way to do it. On July 17, 2018, however, two citizen scientists 400 kilometers apart took images of the same STEVE event.

Origin in the magnetic field

These photos were taken simultaneously from two different angles, so the study authors were able to obtain the exact location of each point in the images by triangulation. This is how they realized that the purple and green emissions are located along the same magnetic field lines.

Despite this alignment, the two colors are at different altitudes. “Our analysis indicates that the purple and green STEVE emissions are driven by the same narrow region, so it must be the magnetosphere,” says Xiangning Chu, a researcher at the Atmospheric and Space Physics Laboratory at the University of Colorado at Boulder. .

According to the scientist, this corroborates an earlier study by the same team, “which provided evidence that the STEVE motor region is located at a sharp edge in the magnetosphere marked by strong waves and particle acceleration.” Although coupling is normally only considered at high latitudes, research results indicate that strong coupling can also occur at lower latitudes.

Chu will present the team’s analysis at the American Geophysical Union’s fall 2021 meeting.

Source: AGU, LASP