[TowerTalk] lightning & trees

[Jim Lux]

At 09:32 AM 3/18/2005, doc wrote:
>Im my mind the laws of physics are predictable else they are not
>laws.  I believe that the physical universe is balanced and
>orderly, even if there remain many facets we have yet to
>comprehend due to the complexities of inter-related variables.
>
>While the variables may be multiple and difficult to identify
>and to predict they are nonetheless available to identification
>and predictability.
>
>My questions go to whether scientists yet understand them or
>if this is one of the areas where they are still learning.
>
>It would logically follow that knowing the how of streamers
>would provide the building blocks upon which mitigation techniques
>may be developed.
>
>Postulating that lightning and related elements (e.g. streamers)
>are unknowable (and/or random) sounds more like mysticism than
>science and that is what has been making me uncomfortable.
>
>;-) doc

The precise direction streamers will move is effectively random, in that it 
is largely influenced by very small scale changes in the ionization of the 
gas, typically the result of a random cosmic ray or some such.

Imagine a perfect sphere of charge with enough charge for the surface to be 
just under breakdown (30kV/cm roughly).  Now imagine a cosmic ray, or some 
other random irregularity (dust particle, ice crystal, etc.) that changes 
the field next to the sphere.  The breakdown will start there.  The current 
will flow, changing the fields, etc.etc.etc.

Measuring breakdowns in a lab environment, one uses an external source of 
ionization (i.e. short UV or radioactive source) to reduce the variability.