What’s That Noise? 11 Strange and Mysterious Sounds on Earth & Beyond – Live Science

The ephemeral sounds made by the northern lights have been heard by many skywatchers and winter wanderers, usually on very clear and still nights when the auroras are at their most powerful.

The faint sizzling, popping and crackling sounds heard overhead during auroras have long defied a scientific explanation. The sounds are very faint when heard on the surface, so researchers have puzzled over how they could be made by the auroras, which occur high in the outer atmosphere, hundreds kilometers above the Earth’s surface.

Unto Laine, an acoustician in Finland, has been able to make the first known recordings of the sound of the auroras, and he now thinks he’s found a scientific explanation. [Read full story about the sounds of the northern lights]

By using an array of microphones to triangulate the location of the sounds, Laine pinpointed the origin of the eerie noises in a relatively low level of the atmosphere, at around 230 feet (70 meters) above the ground.

Laine thinks the sounds are caused by regions of electrical charge building up in the atmosphere across a so-called thermal inversion layer, which can form in many areas on very calm and clear nights.

When the layers of electrical charge are disturbed by magnetic storms that supercharge the northern lights, they discharge with a small spark in the atmosphere, causing a faint but steady popping or crackling sound that can be heard at the surface when conditions are right.

Next up: To the moon!

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