Ken,
Here is more on this from Wikipedia:
"An average bolt of negative lightning carries an electric current of 30,000 amperes ("amps") — 30 "kiloamps" (kA), and transfers five coulombs of electric charge and 500 million joules — 500 "megajoules" (MJ) of energy. Large bolts of lightning can carry up to 120 kA and 350 coulombs.[14] The voltage is proportional to the length of the bolt.
An average bolt of positive lightning carries an electric current of about 300 kA — about 10 times that of negative lightning."
"Positive lightning
Positive lightning is a type of lightning strike that comes from apparently clear or only slightly cloudy skies; they are also known as "bolts from the blue" because of this trait. Unlike the more common negative lightning, the positive charge is carried by the top of the clouds (generally anvil clouds) rather than the ground. The leader forms in the sky travelling horizontally for several miles before veering down to meet the negatively charged streamer rising from below. Positive lightning makes up less than 5% of all lightning strikes.[42] Because of the much greater distance they must travel before discharging, positive lightning strikes typically carry six to ten times the charge and voltage difference of a negative bolt and last around ten times longer.[43] During a positive lightning strike, huge quantities of ELF and VLF radio waves are generated.[44]
As a result of their greater power, as well as lack of warning, positive lightning strikes are considerably more dangerous. At the present time, aircraft are not designed to withstand such strikes, since their existence was unknown at the time standards were set, and the dangers unappreciated until the destruction of a glider in 1999.[45] The standard in force at the time of the crash, Advisory Circular AC 20-53A, was replaced by Advisory Circular AC 20-53B in 2006,[46] however it is unclear whether adequate protection against positive lighting was incorporated.[47][48]
Positive lightning is also now believed to have been responsible for the 1963 in-flight explosion and subsequent crash of Pan Am Flight 214, a Boeing 707.[49] Due to the dangers of lightning, aircraft operating in U.S. airspace have been required to have lightning discharge wicks to reduce the damage by a lightning strike, but these measures may be insufficient for positive lightning.[50]"
Source: http://en.wikipedia.org/wiki/LightningOn Fri, Oct 1, 2010 at 12:18 AM, Ken Swain <peavine15@yahoo.com> wrote:
I wasn't aware there WAS such a thing...thanks for the info
--- On Thu, 9/30/10, Kim Noyes <kimnoyes@gmail.com> wrote:
From: Kim Noyes <kimnoyes@gmail.com>
Subject: [californiadisasters] Possible Positive Bolt in Chula Vista Today
To: "CaliforniaDisasters" <californiadisasters@yahoogroups.com>
Date: Thursday, September 30, 2010, 10:23 PM
This afternoon in Chula Vista in San Diego County a lightening bolt struck a water main damaging it and blew out several nearby windows.
I do not know if this bolt struck a hydrant and then followed that down to the main or if it directly impacted the ground and traveled down through the soil and contacted the main that way.
Given what typically happens as a result of the much more garden variety and significantly weaker negative bolts I'd say this was a positive bolt although I cannot confirm that.
Kimmer![]()
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