Earth emits awful sound into space

Scientists have known about the radiation since the 1970s. It is created high above the planet, where charged particles from the solar wind collide with Earth's magnetic field. It is related to the phenomenon that generates the colorful aurora, or Northern Lights.

The radio waves are blocked by the ionosphere, a charged layer atop our atmosphere, so they do not reach Earth. That's good, because the out-of-this-world radio waves are 10,000 times stronger than even the strongest military signal, the researchers said, and they would overwhelm all radio stations on the planet.

Theorists had long figured the radio waves, which were not well studied, oozed into space in an ever-widening cone, like light from a torch.

But new data from the European Space Agency's Cluster mission, a group of four high-flying satellites, reveals the bursts of radio waves head off to the cosmos in beam-like fashion, instead.

This means they're more detectable to anyone who might be listening.

The Auroral Kilometric Radiation (AKR), as it is called, is beamed out in a narrow plane, as if someone had put a mask over a torch and left a slit for the radiation to escape.

This flat beam could be detected by aliens who've figured this process out, the researchers say. The knowledge could also be used by Earth's astronomers to detect planets around other stars, if they can build a new radio telescope big enough for the search. They could also learn more about Jupiter and Saturn by studying AKR, which should emit from the auroral activity on those worlds, too.

"Whenever you have aurora, you get AKR," said Robert Mutel, a University of Iowa researcher involved in the work.