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
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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
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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.
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