by The northern and southern lights are among nature’s most remarkable sights, providing beautiful light shows that dance across the night sky – but what exactly is an aurora?
Auroras, also known as the northern lights (aurora borealis) or southern lights (aurora australis), cause solar energy and particles to interact with the Earth’s atmosphere as the planet’s magnetic fields funnel them towards the poles. They are often seen in high latitude regions around the Arctic and Antarctic.
These colorful light displays are usually seen as green bands, but they can also occur in red, blue, violet, pink and white. However, not all light displays seen in Earth’s sky are true auroras. Some purple and white stripes called “STEVE” (Strong Thermal Emission Velocity Enhancement) and a corresponding green on-hour glow that resembles a picket fence with rough points produced by various physical processes that make them different from auroras.
A recent study of the Earth’s atmosphere suggests that electric fields parallel to the Earth’s magnetic field may produce the color spectrum of the picket fence light feature in a region further south than the one where auroras form. Similar processes are believed to produce STEVE, which is often accompanied by streaks similar to a picket fence, according to a statement from the University of California, Berkeley.
“This would improve our modeling of what creates the light and energy in the aurora in some cases,” Claire Gasque, a graduate student in physics at UC Berkeley and lead author of the study, said in the statement.
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Light shows i The Earth’s Atmosphere which is inspired by solar storms and coronal mass ejections (CMEs), which can disrupt the Earth’s magnetic field and funnel ions down towards the poles. Auroras are the result of these ions colliding with oxygen and nitrogen atoms in the Earth’s atmosphere, creating green, red and blue light emissions.
In comparison, STEVE is generally seen as a purple or mauve light, accompanied by a green picket fence – neither of which emit blue light. These phenomena also occur at lower latitudes than auroras.
“If you look at the spectrum of the picket fence, it’s a lot greener than you might expect. And none of the blue that is coming from the nitrogen ionization,” said Gasque in the statement. way out in space down in the atmosphere, because those particles have too much energy.”
Instead, the recent study suggests that STEVE and the picket fence are generated by parallel low-altitude electric fields The Earth’s magnetic field. Using a model of the ionosphere, the researchers showed that a parallel electric field at an altitude of about 68 miles (110 kilometers) could excite oxygen and nitrogen and generate the spectrum of light observed from the picket fence. Auroras, on the other hand, are usually the result of energetic particles at altitudes higher than 621 miles (1,000 km) above the surface.
“The light from the picket fence is created by particles that have to be energized in space by a parallel electric field, which is a completely different mechanism than any of the auroras that we have studied or known before,” said Gasque in the statement.
Another author involved in the study says that this new research could help us understand unknown physical processes in the Earth’s atmosphere. “The really interesting thing about Claire’s paper is that we’ve known for a few years now that Steve’s spectra have been telling us that there’s some very strange physics going on. We just didn’t know what it was,” said Brian Harding, co-author of the paper, in the statement. “Claire’s paper showed that parallel electric fields can explain this exotic spectrum.”
Although the energetic particles produced by STEVE and the picket fence are probably not from the Sunlike auroras, the scrambling of the atmosphere caused by solar storms is still believed to be triggering the light all the same, according to the study.
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Next, the researchers plan to send a rocket through these night sky phenomena to measure the strength and direction of the electric and magnetic fields. And, since these events are triggered by solar storms, the approaching peak solar activity is called “solar maximum“ it provides a unique opportunity to study rare events such as STEVE and the picket fence.
“It’s fair to say that there will be a lot of studies to be done in the future on how those electric fields came about, what waves are associated with them or not, and what that means for the transition more energy between the Earth’s atmosphere and space. ,” Brian Harding, co-author of the paper and assistant research physicist at UC Berkeley’s Space Sciences Laboratory (SSL) said in the statement.
Their results were published November 3 in the journal Geophysical Research Letters and will be presented at a meeting of the American Geophysical Union in San Francisco on December 14.
