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Sferics and Natural Radio
| 282RA | 31 May 06 - 06:54 PM | |
| Amos | 31 May 06 - 07:44 PM | |
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Sferics and Natural Radio
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Subject: Sferics and Natural Radio From: 282RA Date: 31 May 06 - 06:54 PM This is the man formerly known as GUEST, AR282. I can't remember my old password, I give up. So I created a new ID. Below are links to various sites concerning natural radio, that is, ELF and VLF frequencies. In this range, earth's magnetosphere can be tuned into. Auroras can cause all interesting manner of disturbances that send ripples through the magnetosphere that we can listen in on as radio signals. But we are mainly dealing with "sferics" when we use natural radio. Sferics describes the process of lightning strikes happening all over the earth which makes a constant background noise while listening to natural radio. You can verify this yourself by tuning your AM band to some blank part of the dial. The crackles you hear are lightning strikes, some of them from halfway around the earth. When these strikes disturb the plasma flux of the magnetosphere—earth's magnetic field—the separate flux bands carry separate frequencies of the lightning strike and they race around the earth in seconds and rebound. The high frequencies arrive first and then progressively lower frequencies. The radio signal sounds like a descending whistling tone and called a "whistler." There are all kinds of sferics besides whistlers—auroral chorus, dawn chorus, tweeks, solar flares, hiss, saucer, AKR etc. In fact, whistlers are comparatively rare and some believe that they are only caused by upward-moving lightning, according to one source. I took that to mean a sprite so I included a wonderful site about sprites. It's interesting to look at photos of sprites and listen to the sound of a whistler at the same time. It's almost like a living creature with its own amazing cry. Eerie really. Other planets, distant stars and galaxies make different sounds. One site listed below provides very cool samples of Jupiter, the sun and pulsars (spinning dead stars beaming out random energy in pulses). In fact, radio is an excellent tool by which to map the universe and the first people to do it were radio engineers and enthusiasts rather than astronomers. You'll read about them in the links below. We've even tuned in on the Big Bang by picking up its primordial reverberations via radio. Provided in the links are sound bytes of various atmospheric phenomena accessible to our senses only via radio. Some of the chorus samples sound very much like someone speaking but you can't quite make out what they're saying. But it's not a voice, it's a random signal. Others sound surprisingly like twittering birds and some sound like drops of water falling in an echo chamber or something. One of the pulsar samples sounds like someone stomping on a hard floor in hard shoes in a very deliberate, rhythmical manner. The sounb byte of the solar electromagnetic energy sounds like a train going over tracks and, for a real mind-blower, give a listen to the end of Hendrix's "3rd Stone from the Sun." You may want to bookmark these, you never know when you'll want to hear the universe talking, singing, crying, moaning, sighing, giggling, chirping, snoring, marching, farting, belching, whistling and grumbling again. Unfortunately, I can't seem to post clickable links here but you can copy them and paste them in your browser window and have yourself a ball! http://image.gsfc.nasa.gov/poetry/sounds/sounds.html http://www-pw.physics.uiowa.edu/plasma-wave/istp/polar/home.html http://www-star.stanford.edu/~vlf/Science/Science.html http://www.pulseplanet.com/archive/Mar03/2881.html http://www.altair.org/natradio.html http://science.nasa.gov/newhome/headlines/essd10jun99_1.htm |
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