Barry,
I believe Ross is right for the last and larger half (LARGER half??
{poetic license}) of a lightning strike. As I understand the current
lightning model the initial strike is a positive "Leader" coming from the
cloud to the ground. The Leader is a thin column of air that has been
ionized by the excessive potential between the cloud and ground. The
electrons move back towards the cloud, the positive air (nitrogen, oxygen,
water vapor, etc.) ions move towards the ground breaking down the air and
creating more ions as they go. The path is dependant on the instantaneous
breakdown potential of the closest air molecules to the leader causing the
characteristic jagged nature as it comes down. Once the leader reaches the
earth (tree, building, dirt...) The excess electrons rush back to the cloud
along the ionzed leader.
The lightening is a positive stroke downward followed by a large
Negative stroke upwards.
Paul McCoy
"Lichtenstein, Ross" <[email protected]>@ieee.org on
10/05/2000 09:54:21 AM
Please respond to "Lichtenstein, Ross" <[email protected]>
Sent by: [email protected]
To: "'Barry Ma'" <[email protected]>, [email protected]
cc:
Subject: RE: Electron Flow
Barry,
I could be wrong, and if so I would stand corrected, but from my basic
electronics training,
I recall that electron flow is from negative to positive.
I also recall being taught that lightning actually travels from earth (neg.
charge) upward
to the positive charge of the clouds. Then there is also the case of
lightning between clouds
of opposite charge, and again the electron flow direction is from neg. to
pos.
Ross
-----Original Message-----
From: Barry Ma [mailto:[email protected]]
Sent: Wednesday, October 04, 2000 5:58 PM
To: [email protected]
Subject: Re: ESD Opportunities
Please allow me to ask a relevant question only for curiosity.
We have no idea of what charge (positive or negative) would go to the DUT
in
ordinary ESD.
That's why we have to test two polarities in ESD immunity test.
Lightning is a kind of ESD happened between a charged cloud and objects on
earth surface. Some figures imply that an electron current flows from the
charged cloud to the earth. Is it possible to have an opposite direction -
electron flows from earth to cloud?
Thanks.
Barry Ma
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