Scientists discover the powers of the celestial phenomenon STEVE

The celestial phenomenon known as STEVE is probably caused by a combination of heating charged particles in the atmosphere and energetic electrons like those that fuel the aurora, according to new research. In a new study, scientists discovered the source region of STEVE in space and identified two mechanisms that cause it.

Last year, dark atmospheric lights became an Internet sensation. The typical aurora, the north and south lights, are generally perceived as swirling green ribbons that extend into the sky. But STEVE is a thin ribbon of rosy or mauve red light that stretches from east to west, farther south than the aurora usually appears. Even stranger, STEVE is sometimes joined by vertical green light columns nicknamed the "palisade".

Auroras are produced by glowing oxygen and nitrogen atoms in the upper atmosphere of the Earth, excited by charged particles from the magnetic environment near the Earth, called the magnetosphere. Scientists did not know if STEVE was a kind of dawn, but a study in 2018 revealed that its glow was not due to charged particles flowing into the upper atmosphere of the Earth.

The authors of the 2018 study nicknamed STEVE a kind of "sky glow" distinct from the dawn, but did not know exactly what caused it. The fact that STEVE can appear during magnetic storms caused by the sun around the Earth and feeding the highest auroral lights further complicates the situation.

Authors of a new study published in the journal of AGU Geophysical Research Letters analyzed satellite data and ground images of STEVE events and inferred that the red arc and the green palisade are two distinct phenomena stemming from different processes. The picket fence is caused by a mechanism similar to that of typical aurora, but the purple streaks of STEVE are caused by the heating of charged particles higher in the atmosphere, which causes the bulbs to burst.

"Aurora is defined by the precipitation of particles, electrons and protons falling into our atmosphere, while the atmospheric glow of STEVE comes from heating without precipitation of particles," said Bea Gallardo-Lacourt, physicist of space at the University of Calgary and co-author of the book. new study. "The electrons that cause the green fence are therefore auroras, although this happens outside the auroral zone, so it's really unique."

STEVE's images are beautiful in themselves, but they also offer a visible way of studying the invisible and complex fluxes of charged particles in the Earth's magnetosphere, according to the study's authors. The new findings help scientists better understand how particle fluxes develop in the ionosphere, which is an important goal, as such disturbances can interfere with radio communications and affect GPS signals.

Where does STEVE come from?

In the new study, the researchers wanted to know what STEVE's powers were and if that happened in both the northern and southern hemispheres. They analyzed data from several satellites that flew over during the STEVE events of April 2008 and May 2016 to measure the electric and magnetic fields of the Earth's magnetosphere at that time.

The researchers then linked the satellite data with photographs of STEVE taken by amateur amateur photographers to determine the causes of this unusual brightness. They discovered that during STEVE, a flowing "river" of charged particles in the Earth's ionosphere collided, creating a friction that warmed the particles and caused them to emit a purple light. Incandescent bulbs work in much the same way, where electricity heats a tungsten filament until it is hot enough to shine.

It is interesting to note that the study revealed that the fence was powered by energetic electrons moving from space to thousands of kilometers from the Earth. Although similar to the process that creates typical auroras, these electrons have an impact on the atmosphere far south of the usual auroral latitudes. Satellite data showed that high-frequency waves moving from the Earth's magnetosphere to its ionosphere could give energy to the electrons and eject them from the magnetosphere to create the display of the striped picket fence.

The researchers also found that the palisade was in both hemispheres at the same time, which supports the conclusion that its source is high enough above the Earth to feed both hemispheres simultaneously with energy.

Public participation has been crucial for STEVE's research by providing ground-based images and accurate data on the time and location, according to Toshi Nishimura, Boston University Space Physicist and author principal of the new study.

"As commercial cameras become more sensitive and the excitement generated by the dawn spreads via social media, citizen scientists can play the role of" mobile sensor network ", and we are grateful to them for providing us with data to analyze, "said Nishimura.