This is a very serious topic, can I refer the group once again to a book
published in 2008 called "The Art and Science of Lightning Protection" The
author, Professor Martin A. Uman PhD is a very experienced and respected
lightning specialist based in Florida. The book ISBN code is
Sicerely, John. G3JVC.
[mailto:email@example.com] On Behalf Of David Gilbert
Sent: 29 April 2010 07:28
Subject: Re: [TowerTalk] US Tower damaged by lightning
The last time this topic came up somebody made the distinction between
positive and negative lightning, so I did some Google searching on it
and found a ton of information on it ... most of it pretty scary.
There's even a Wikipedia page on it. If I remember correctly, positive
lightning carries at least ten times the amount of energy as normal
lightning, part of it in the form of higher voltage but most of it in
the form of much higher current. It pretty much fries everything in its
path and is truly wicked stuff. It occurs pretty much randomly among
normal lightning at something approximating a 5% -10% rate (again from
my memory), and is known for being able to travel horizontally long
distances to reach ground.
The Intellicast website includes a quasi real time map of lightning
strikes across the U.S., and they distinguish between negative and
positive strikes by using different colors (yellow for negative and red
for positive). I check that site quite often during our summer
lightning season here in southern Arizona and the red dots show up more
often than any of us would probably like to see.
On 4/28/2010 10:48 PM, Roger (K8RI) wrote:
> However there is lighting and then there is lightning. The power in
> lighting bolts varies tremendously by several orders of magnitude.
> There there are the so called "super strikes" that are many times more
> powerful than most lightning. They are not only more powerful than
> regular lightning, the main power is down instead of up and they are
> usually associated with "sprites", which are seen well above the tops of
> the clouds and extending into space. These are the ones that blow holes
> in big airplanes and are very destructive. A well laid out ground system
> that would eliminate damage from garden variety lightning may lessen the
> damage, but there is little that will protect from these.
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