Earth screeches, scratches in melody on the Web

Lightning is the main melody maker in the music of the Earth

By Richard Stenger
CNN

(CNN) -- Want to hear music that is really down to earth? Check out a Web site that broadcasts the perpetual piping of our planet. The sound is rather striking.

The screeches, blasts and hums that comprise the terrestrial tune are actually natural radio emissions that constantly surround us. But radio antennae, not ears, are required to listen.

Using a very low frequency radio (VLF) receiver, NASA tunes in to the sounds and broadcasts them on the Internet from Huntsville, Alabama, home to the agency's Marshall Space Flight Center. To hear a sample or listen to the online receiver, visit the following NASA page:

• http://www.spaceweather.com/glossary/inspire.html

"Everyone's terrestrial environment almost literally sings with radio waves at audio frequencies," said Dennis Gallagher, a NASA physicist.

The main melody emanates from lightning strikes, even from far away, which pulse great distances through the atmosphere and register as strange sounding crackling.

The sound resembles that of frying bacon, similar to the audio bursts on conventional radios, unleashed by nearby lightning bolts. Lightning strikes somewhere on the planet about 100 times per second, meaning the strange-sounding VLF signals are heard constantly.

"The best time to listen is usually around sunset or dawn (Huntsville time)," when the atmosphere amplifies the natural radio waves, Gallagher said. Moreover, night is generally a better time to listen than during the the day.

Space scientists classify different lightning sounds as "sferics," short for atmospherics, "tweeks" and "whistlers," depending on their intensities and the convoluted paths they take before reaching the receiver.

"Lightning pulses that travel all the way to the magnetosphere and back are highly dispersed," said Gallagher. "We call them 'whistlers' because they sound like slowly descending tones."

Digital radio satellite launched from sea
March 19, 2001
Sun flips magnetic field
February 16, 2001

NASA
NASA online VLF receiver

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