Scientists believe they have confidently proven the formation mechanism behind the aurorae, the northern and southern lights visible in the night sky at higher latitudes. In particular, researchers have recreated the mechanism in the lab. It all points out to a single culprit: Powerful magnetic waves known as Alfvén waves that accelerate electrons traveling on the magnetic field lines of the Earth before slamming on the atmosphere.

As reported in Nature Communications, the team used the Large Plasma Device to recreate the waves. They witnessed as electrons were able to not only travel over those waves but to take energy from them, accelerating. These electrons can reach around six percent of the speed of light and by slamming into oxygen and nitrogen atoms, they create the colorful waving curtain effect we see in aurorae.

“Measurements revealed this small population of electrons undergoes ‘resonant acceleration’ by the Alfven wave’s electric field, similar to a surfer catching a wave and being continually accelerated as the surfer moves along with the wave,” co-author Professor Greg Howes, from the University of Iowa, said in a statement.