Auroras, shimmering bands of light that cross the night sky near Earth’s poles, can follow patterns called arcs.
By Jackie Flynn Mogensen edited by Claire Cameron
Green auroral arcs stretch across northwest Canadian skies in 2019
Neil Zeller/NASA
Join our community of science lovers!
Auroras are nature’s most special light show: When charged particles from the sun hit our atmosphere, they can generate vibrant colors that dance across the night sky near Earth’s poles. The aurora can enter various shapesincluding strips, spokes, patches and more.
But why auroras form these patterns is less clear. Now, researchers say they have identified the “battery” that powers at least one type of aurora: aurora arcs.
A green auroral arc appears above the clouds in this photo taken by an astronaut aboard the International Space Station in 2014.
NASA
On supporting science journalism
If you enjoy this article, please consider supporting our award-winning journalism by subscribe. By purchasing a subscription, you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
In a new study published In Natural communicationsscientists describe how charged particles in our atmosphere are powered by “Alfvén waves,” a special type of plasma wave that travels along Earth’s magnetic lines and acts like a “space battery.” according to NASA. Auroral arcs form when fast electrons, powered by Alfvén waves, hit atoms in our atmosphere, releasing light in towering bands.
A panorama of the Northern Lights in the northern, eastern and southern skies on February 27, 2025, near Churchill, Manitoba.
Photos VW/Getty
The discovery was something of a fluke, made possible by synchronized measurements of an auroral arc in 2015 by military and NASA spacecraft. “These combined observations provided different viewpoints over a long enough period of time to reveal more about the conditions in space that helped create the arc,” NASA said in a statement.
Even though the last cycle of the sun’s activity probably already reached a peakabundant auroras are still expected in 2026, with the season for the northern hemisphere extending into March.
It’s time to defend science
If you enjoyed this article, I would like to ask for your support. Scientific American has been defending science and industry for 180 years, and we are currently experiencing perhaps the most critical moment in these two centuries of history.
I was a Scientific American subscriber since the age of 12, and it helped shape the way I see the world. SciAm always educates and delights me, and inspires a sense of respect for our vast and magnificent universe. I hope this is the case for you too.
If you subscribe to Scientific Americanyou help ensure our coverage centers on meaningful research and discoveries; that we have the resources to account for decisions that threaten laboratories across the United States; and that we support budding and working scientists at a time when the value of science itself too often goes unrecognized.
In exchange, you receive essential information, captivating podcastsbrilliant infographics, newsletters not to be missedunmissable videos, stimulating gamesand the best writings and reports from the scientific world. You can even give someone a subscription.
There has never been a more important time for us to stand up and show why science matters. I hope you will support us in this mission.
