I feel compelled to interject, having some experience in the area of lightning. It's true that the majority of lightning return strokes are negative. However, positive return strokes, usually occurring toward the end of a storm, do occur. They also tend to have a larger magnitude, on average, than the more common negative return strokes. DB
> ---------- > From: [email protected][SMTP:[email protected]] > Reply To: [email protected] > Sent: Thursday, October 05, 2000 9:46 AM > To: Lichtenstein, Ross > Cc: 'Barry Ma'; [email protected] > Subject: RE: Electron Flow > > > > 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 > > _______________________________________________________________________ > > Free Unlimited Internet Access! Try it now! > http://www.zdnet.com/downloads/altavista/index.html > > _______________________________________________________________________ > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > > > -------------------------------------------> > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > > > > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
