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Pythagorean

Infrasonic Lightning

I'm studying lightning as an undergrad in an infrasound research group. I've been doing a lot of reading up on the subject and there seems to be a statement projected through from the '20's with no real evidence (just theoretical predictions) that some of the sound we detect in the low frequencies (1-20Hz) comes from the "readjustment" of the cloud as the lightning lowers charge to Earth.

From the theoretical work, a rarefaction would be produced, as the cloud collapsing on itself (a bit) would create an initial negative pressure wave. However, we don't see this rarefaction at all (and neither have others).

Does anyone here have experience with lightning or is otherwise willing to conjecture as to whether the readjustment of the cloud should create significant infrasonic signals?
billiards

Hi Pythagorean, good to see you here!

You have presented a very interesting phenomenon that I was previously unaware of. Needless to say, I do not have experience with lightning and the sonic properties of a flash.

Certainly it is possible that a sudden compression could cause a sound wave to propagate; I have no trouble believing that this low frequency sound energy is propagated. I don't see why it couldn't be from the actual compression of air from the actual bolt (which is hotter than the surface of the Sun).
Pythagorean

billiards wrote:

Certainly it is possible that a sudden compression could cause a sound wave to propagate; I have no trouble believing that this low frequency sound energy is propagated. I don't see why it couldn't be from the actual compression of air from the actual bolt (which is hotter than the surface of the Sun).


The literature generally attributes the higher frequency sound to the expansion of the lightning channel (what you're talking about) and past authors have claimed that the "cloud readjustment" should contribute to the sound too.

Personally, I don't think it would necessarily cause a uniform contraction that would cause a perfect rarefaction if it were from this "readjustment".

The general consensus among my professors is that the expanding lightning channel probably contributes to the infrasound and the cloud readjustment is negligible.

I don't bring this up out of a serious need for an answer... just interesting discussion.
Baywax

This is a fascinating study. Lightning is very powerful!

Is there anyway to create a control and separate a cloud readjustment
(simulating it somehow) from the voltage?

I'm not at all familiar with the physics of the phenomenon do clouds
readjust without lightning taking place?

Or is it only the pressure created by the charge that readjusts clouds?
If there was a way to somehow approximately simulate the pressure of a charge taking place (without one) on some clouds you might get infrasonic waves. But

How much infrasonic disturbance can readjusting clouds and some
opposing pressures make? Sort of like......."hissssss"?
Pythagorean

Baywax wrote:
This is a fascinating study. Lightning is very powerful!

Is there anyway to create a control and separate a cloud readjustment
(simulating it somehow) from the voltage?

I'm not at all familiar with the physics of the phenomenon do clouds
readjust without lightning taking place?

Or is it only the pressure created by the charge that readjusts clouds?
If there was a way to somehow approximately simulate the pressure of a charge taking place (without one) on some clouds you might get infrasonic waves. But

How much infrasonic disturbance can readjusting clouds and some
opposing pressures make? Sort of like......."hissssss"?


The idea is that as the clouds charge up, the like charges repel. On the other hand, there's multiple layers of charge in a cloud, so the opposite charges will attract (however, the like charges are closer together).

I couldn't really answer any of your questions as I only analyze infrasonic data. There's been some lab experiments with electricity (basically a scientific spark plug) but I'm not sure about lightning clouds, or even clouds alone.

There's still two theories as to how charge even accumulates in a cloud, so there's a great deal of uncertainty involved. They often compare a lightning strike to icebergs. The strike you see form Earth is just the "tip of the iceberg". There's a whole complicated structure of charge (that's different with different clouds) inside the cloud.
Baywax

I forgot that it is the clouds generating the charge. I couldnt begin to understand whats going on with that! The whole premise offers incredible potential as a source of power though. Clouds, the lightest, most powerful generators on earth.

Razz
Pythagorean

Baywax wrote:
I forgot that it is the clouds generating the charge. I couldnt begin to understand whats going on with that! The whole premise offers incredible potential as a source of power though. Clouds, the lightest, most powerful generators on earth.

Razz


Actually, I remember reading that a lot of the energy is expended throughout the atmosphere in acoustics and heat (and even some radiation).

The calculation of actual energy we could get from each strike is about 10^9 Joules or enough to power four 100W lightbulbs for a month.

I think Hydro is the best natural power source.
Baywax

Yes, Hydro is very powerful.

I cant watch this vid right now but it might be interesting for you. Its title is Lightning Energy Source

http://www.youtube.com/watch?v=1yyIpD_sMFs

Heres what Ive found about lightning as energy source

Quote:
Voltage: A typical lightning bolt bridges a potential difference (voltage) of several hundred million volts.

A typical lightning bolt may transfer 1020 electrons in a fraction of a second, developing a peak current of up to 1000 kiloamperes.

Current: Most measurements have been in the range 5,000 to 20,000 amps. Currents over 200,000 amps have been reported.
Hot v Cold Lightning: Most commonly, the lightning current ceases in about a millisecond for a given stroke, but sometimes there is a continuing current on the order of 100 amps following one or more of the strokes. This is called "hot lightning" and it is the cause of lightning fires according to Uman.

The temperatures of lightning are 8,300-33,000°C for both "cold" and "hot" lightning - it is the continuing current that starts some 10,000 fires per year in the U.S. in the estimation of Uman.

Total power: A moderate thunderstorm generates several hundred megawatts of electrical power.


and

Quote:
General Power

One strike has enough energy to light 150,000,000 light bulbs. (Discovery.ca; May 17)

The following data is from an Atlanta Journal article (cited here)

About 95 people die from lightning yearly in the U.S.

A single thunderstorm can release 470 million litres of water (that's the volume of 16 Washington Monuments).

One storm can discharge enough energy to supply the entire U.S. with electricity for 20 minutes

A large Midwestern cumulonimbus can tower 20-25 km (Mount Everest is 8.8 km high.)

There are approximately 2,000 thunderstorms at any given moment worldwide.


There's more!

Quote:
Building A Lighting Harnessing Power Plant

How hard would it be to build a power plant that harnesses the electricity generated by lightning? Then, store the electricity and use it on-demand on the electric grid? Pie-In-The-Sky?
This concept is perhaps not as impractical as it once was. The main limiting factor of implementing a lightning capturing scheme such as this was the inability to be able to store large amounts of electricity for later use. However, new Utility Scale Battery technology or other energy storage technologies such as Flywheels or Capacitors could be used to store the electricity captured from lightning in massive quanties, for later grid use.
Obviously, a lightning capturing power plant would only be practical in regions with frequent thunderstorms, such as Florida.
How hard would it be to build an array of lighting rods to capture periodic thunderstorm electricity? The biggest hurdle would really be creating power plant infrastructure that could survive the harsh surges created by lightning strikes, but even that seems possible with current technology and materials. Electrical and building design engineers could come up with an innovative way to make it work. Specially designed buffer/insulation and transformer materials could be used to safely capture and harness the massive amounts of electricity generated during a lighting strike, and transfer it to large storage device for later use.


I recommend visiting the site where I got this info. There's a diagram of the set-up for storing the energy of a lightning strike and a lightning storm...... it uses the Tesla Coil among other rather simple techniques.

http://peswiki.com/index.php/Directory:Lightning_Power

I can't say I had any hope that this would be a source. But, this info appears to offer some.

Sorry to digress from the Infrasonic Lightning topic. How about using Infrasonic waves to turn a turbine?!

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