Electrical Properties of Lightning

[Rob Wadsworth]

I have been looking on the web to find out the known specific properties of lightning. I have been looking thru a lot of sources; but the answers are a bit unclear.

So far, I have seen one article that stated that lightning is over a million volts @ 3000 amps - at/around 2mhz in wavelength.
Wha?
Another article pointed out that the amperage is around 250,000.

I'm sure that there are enough Met grads out there that can help me fill in the blanks.
I would appreciate a definitive answer.

re:another forum on Ham/CB radios needs definitive info on grounding one's home and radio station in a suitable fashion to make the building safe from a possible fire due to insufficient grounding procedures.

EDIT: I found this; would anyone care to agree/disagree with is info found in the 'properties' chapter?
http://en.wikipedia.org/wiki/Lightning

Thanks!

 

[Mark Ellinwood]

There are many proposed ranges for current/width/length/heat/etc.

A former professor of mine, Vince Idone, is a lightning expert, and suggested these types of parameters:

Current: 50k-400k amps
Path Width: 0.5-1.5 inches
Length (per step): 50-100 meters
Time interval between steps: ~50 microseconds
Air heating: ~50,000 F

I love lightning myself, so I've done my research with this stuff, and found that the above-listed parameters is the general mean, with the exception of the path width. However, considering Vince spent years photographing lightning with high-speed cameras, I'd go with what he said

 

[Stephen Locke]

path width

Well most of the parameters are so abstract to me I don't try to comprehend them but as a visual guy I've often wondered how wide a lighting stroke is. The image below records a double stroke. With Marks proposed ranges the smaller stroke in this image is .5 inches wide while the wider stroke is 1.5 inches wide. I'm wondering how you could possibly measure that in the field. I guess you you could do a controlled laboratory measurement and extrapolate up from there to propose the width of an anvil bolt . . .
Image is extra large so you can magnify it if your browser does not present full size.
Image

I realize optics and atmospheric distortion contribute to the final image but if you compare the lighting stroke to the tree trunk the stoke width (if taken literally) could be measured in feet.

 

[Rob Wadsworth]

Well, I know that fulgurites (a mineral tube in the shape of lightning found in the ground after a lightning strike - composed mostly of crystallized silicon formed due to extreme heat and current) exists between those .5 to 1.5 inches/diameter. The lengths vary. That may be only one means to be used to infer that width.
http://www.minresco.com/fulgurites/fulgurites.htm
http://en.wikipedia.org/wiki/Fulgurite

I'm trying to determine how much current a single strike of lightning creates.
Just one of the pulses; not all.
X amount of volts times X amount of amps will equal X amount of watts.
I am also trying to find out how commercial broadcast stations deal with lightning striking their towers.
Grounding, arrestors, wiring procedures, etc...

 

[Jason Tunzer]

I'm going to go with Professor Doc. Brown and say 2.21 gigawatts.

 

[Dan Robinson]

I would highly recommend any books and publications by Martin Uman, Vladmir Rakov and Richard Orville. They cover this subject in both simple terms and in great detail depending how deep you want to delve into it.

A lot of their material can be viewed in Google Books via a search for their names.

 

[Matt.Elliott]

I would highly recommend any books and publications by Martin Uman, Vladmir Rakov and Richard Orville.

I would also like to recommend "The Electrical Nature of Storms" by my GRA advisors Dr. MacGorman and Dr. Rust.

 

[John Hudson]

Let's not forget the humbling power of the superbolt - positive lightning - the bolt from the blue that carries an almost incomprehensible electrical current.

The following facts are gleaned from the lightning section of my book:

-Approximately 5% of lightning strikes are positive
-Estimated average voltage of a positive strike: 1 gigavolt
-Estimated average current of a positive strike: 300 kiloamperes
-Positive strikes have a duration of hundreds of microseconds, making them more deadly and destructive than their negative counterparts that last on the order of 30 microseconds.
-Estimated average peak output of a negative lightning discharge: 1 terawatt
-Estimated peak temperature of the lightning channel: 38,000 deg. Fahrenheit

For information on lightning protection systems for the TV and radio broadcast industry, the following link provides a wealth of information: http://www.lbagroup.com/international/lightmas.php

Hope this helps a little.


John Hudson
VE4 JTH

 

[Rob Wadsworth]

Appreciate that info/link J. Hudson.

A bolt from the blue; yes I am familliar with that phenomena. First time I've seen figures for it.
Great!

It is supposed to be the most dangreous form of lightning - as it can strike many miles from the parent thunder storm. Up to fifteen miles away or even more - from accounts that I've read.