In message , Les Hellawell
writes
Sorry if you think this a bit long but I think lightning is an interesting
subject and, as it involes TV aerials relevant to the newsgroup.

"Les Hellawell" wrote in message news:...

"M. J. Powell" wrote in message

In message , Les Hellawell
writes
This requires length explanation:

The conditions for a lightning occurs when friction between moving
layers of atmosphere, strip electrons from atoms in the top layer.
(ie a cold layer of air pushes under a warm moist layer forcing it
upwards. The warm air cools rapidly and dumps its moisture as rain)
Static electricity. The electrons are grounded and concentrate in the
ground immediately below the mass of electron deficient atoms above
as they seek to return*.

The other way round actually, the cloud is negatively charged, the
ground is positive. The effect is the same.

Electron deficient atoms are positively charged
whilst electrons are negatively charged. As the friction continues the
potential difference across the intervening layer of air increases to a
point when breakdown of its insulation occurs. (sheet lightning occurs
when the electrons are not grounded but in a separate area of sky).

This predicates that a ground strike can only occur when it's raining?

No, they generally occur at the same time but are separate
phenomena created by the one circumstance.

I have been doing some further reading into the causes and effects
of lightning and it is possible that you may be correct in some
circumstances. My previous EMail was based on research that I read
more than twenty years ago: (including Nelkon: Principles of Physics)
A great deal more research has been done since.

Thanks very much for the explanation.

Snipped

I have a VHS recording of a Horizon programme about lightning research
in the US. Part of it shows a slo-mo recording of a lightning strike.
You can clearly see the leader starting up from the ground towards the
cloud, closely followed in time by the main downflash along the same
path.

Mike
--
M.J.Powell