Seeing the northern lights is a common bucket list item, but until very recently, scientists were not completely sure what caused this beautiful luminescent phenomenon. After taking a deeper look at the blue, green, and violet light show, also known as aurora borealis, researchers from multiple universities were able to finally confirm that the light show is caused by Alfvén waves.

According to the study, when disturbances of the sun pull on Earth’s magnetic field, cosmic undulations known as Alfvén waves are caused which launch electrons at high speeds into Earth’s atmosphere where they create the aurora. Imagine the sun tugging on Earth’s magnetic field like a rubber band. This force creates unique waves. 

These Alfvén waves occur about 80,000 miles from the ground and as they get closer to Earth, electrons will hitch a ride on the waves. The force of these hitching electrons colliding with Earth’s upper atmosphere at 45 million miles per hour sends them into an excited state. As they calm, they release the light which forms the northern lights. 

To come to this conclusion, the researchers used the Large Plasma Device at the Basic Plasma Science Facility at the University of California, Los Angeles to simulate the interaction between Alfvén waves and electrons. 

The researchers hope the clarification of the cause of aurora borealis will help us better understand how particles are energized and the sun’s impact on our planet, but more broadly, it’s enchanting to finally know how this beautiful phenomenon takes place. 

“This appeals to our sense of awe and wonder,” said Jim Schroeder, the article’s lead author. “We’ve been captivated by auroras for thousands of years and looking at the night sky and appreciating their beauty. And I’ve always found that understanding more about how something is created enhances my appreciation of that beauty.”

Source study: Nature Communications – Laboratory measurements of the physics of auroral electron acceleration by Alfvén waves