[TowerTalk] Is lightning hitting the tower..or the yagi's

[Andy]

I occasionally scan articles about lightning, but would never consider
myself anything of an expert on it.  And lots of what I've read, I've
surely forgotten over time.  It's not part of my main line of work.

> they are called 'leaders'.

Ah yes.  Thanks for the correction.

> In 'normal' lightning it is a 'negatively charged downward leader' that
> comes out of the cloud.  It progresses in 50-100m jumps as the charge pushes
> it down... Note, I said PUSHES, the ground influence on the leader direction
> is relatively small, it is the gross field gradient between the earth and
> cloud that causes the major movement groundward at about 1/3c.

Amazing that it can accelerate and push particles close to relativistic speeds!

> Positive lightning is well known for causing lots of damage... there are
> several reasons for this, but the biggest one is that it comes from the top
> of the cloud.

I've seen one of the pictures, showing a "bolt in the blue" coming
from the anvil and jumping 20-30 miles away from the storm clouds.
NOAA says distances up to 50 miles or more are possible.

Years ago I read that one dangerous type of lightning is one that
lacks the usual multiple strokes.  Perhaps just the leader and a
single return.  Supposedly these are more likely to hit ground and
blow things up.  I don't know if they are related to positive
lightning.

Since reading that, I have noticed there are storms where the bolts
seem to be singular, not pulsed.

> you don't have to get hit directly to be injured.  It is well known that the
> voltage developed between your feet on the ground is enough to harm you when
> a stroke hits a tree or the ground nearby.  Standing on a metal door
> threshold, or next to a porch light, could have been enough to get a side
> flashover from a stroke that hit the power line or something else nearby.

The case I heard of, would have been in a wooden doorway, probably
with no porch lights.  (This was a LONG time ago.)

Regards,
Andy