Arctic wilderness tales often wax poetic about dazzling displays of northern lights painting the skies. But for at least the past century, some of those stories have also mentioned eerie noises associated with especially powerful auroras.

Witnesses say the sounds are comparable to radio static, like a faint crackling, light rustling, or hissing heard for a few minutes during a strong display. While the weird sounds were long considered folklore, Finnish scientists have not only shown that they really happen, but now the team thinks they know why.

The answer can be traced to charged particles trapped in a layer of the atmosphere that forms during cold nights. These particles rapidly discharge when bursts of material from the sun slam into Earth,