Hearing Lightning Half A World Away |
 Dave Thurlow, Host |
I'm Dave Thurlow and this is The Weather Notebook. You're listening to sounds captured by recordist Steve McGreevy. The sounds of the northern lights and of lightning half a world away. Weather Notebook producer Barrett Golding caught up with Steve in Southern Alberta.
SM: "That was a burst of static from something pretty close...a lightning storm. Oftentimes, when I'm recording, you'll hear kind of a crack and maybe a second or two later you'll hear swoosh.
The electromagnetic pulse from the lightning bolt takes a round trip to the opposite hemisphere and then it bounces back. And in making this long trip the frequency components are spread out, so you get the downward falling tone. These receivers are sensitive enough that a lightning storm can be happening 1,000 miles away and the static will still be strong. You can just hear all the snapping...let me turn on this speaker amplifier.
You can just imagine...there is so much...in fact, we're hearing some nice noises now coming in. OK, this is a very beautiful sounding event. This is called chorus. Particles from the sun are hitting earth's magnetic field and generating these noises, probably several thousand miles out in space. Imagine a soap bubble with wind currents pushing against it. You can see it deform. Well, that's essentially what happens with earth's magnetic field."
The Weather Notebook is supported by Subaru and the National Science Foundation.
The VLF Story - Stephen P. McGreevy
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