From Popular Mechanics
Scientists have new insights into the mysterious celestial phenomena affectionately known as STEVE. They now believe the atmospheric glow of STEVE (Strong Thermal Emission Velocity Enhancement) is created through a “combination of heating of charged particles in the atmosphere and energetic electrons like those that power the aurora,” according to a press statement.
A quick STEVE refresher: Per a 2018 study in Geophysical Research Letters that first examined the curiosity, STEVEs are “extremely narrow ribbons of vibrant purple and white hues” glowing in the night sky. Their color patterns are specific, showing red-pinks arcs, and they’re occasionally joined by green vertical columns that scientists have nicknamed “picket fences.”
Photo credit: Ryan Sault
When amateurs first spotted the strange glow, they called it STEVE, a reference to when characters in the 2006 animated film Over the Hedge discover an unknown entity. While scientists were able to determine that STEVEs aren’t auroras, for a while they couldn’t figure out what they actually were, or how they were formed.
Their best guess was that a STEVE originated in the ionosphere, an upper part of the Earth’s atmosphere. The ionosphere overlaps with Earth’s magnetosphere, the area of space surrounding our planet that’s controlled by its magnetic field. So scientists analyzed data from satellite footage of STEVE events between April 2008 and May 2016 to measure electric and magnetic fields in the magnetosphere.
After matching the data with amateur photos, the scientists-an international team from the U.S. and Canada-developed a theory. Here’s what probably happens during a STEVE, according to the press release:
A flowing “river” of charged particles in Earth’s ionosphere collide, creating friction that heats the particles and causes them to emit mauve light. Incandescent light bulbs work in much the same way, where electricity heats a filament of tungsten until it’s hot enough to glow.
But STEVEs contain multitudes. While the river of charged particles is colliding in the ionosphere, in the magnetosphere, energetic electrons are streaming around Earth. High-frequency waves can knock out of the magnetosphere to the ionosphere, which creates the green picket fences. It’s a process similar to what causes auroras, but in a different location.
What’s the distinction? “Aurora is defined by particle precipitation, electrons and protons actually falling into our atmosphere, whereas the STEVE atmospheric glow comes from heating without particle precipitation,” says Bea Gallardo-Lacourt, a space physicist at the University of Calgary and coauthor of the new study, in the release. “The precipitating electrons that cause the green picket fence are thus aurora, though this occurs outside the auroral zone, so it’s indeed unique.”
Scientists completely missed STEVEs until amateurs brought the odd lights to their attention. Learning about them has been an effort showcasing the strength of amateur-professional scientific alliances.
“As commercial cameras become more sensitive and increased excitement about the aurora spreads via social media, citizen scientists can act as a ‘mobile sensor network,’ and we are grateful to them for giving us data to analyze,” says Toshi Nishimura, a space physicist at Boston University and lead author of the new study, in the release.
STEVEs are far from the only important scientific finds that have been made on commercial devices. In 2013, dashcams proved to be crucial to understanding a small asteroid that struck Russia. And last year, an Italian locksmith captured the first ever shot of a supernova’s first light.
Source: AGU via NewAtlas
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