Strange Spark Phenomena

From:  Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
Sent:  Friday, January 30, 1998 9:46 AM
To:  Tesla List
Subject:  Re: Strange Spark Phenomena

> I too have noted this on a number of occasions with a lot of 
> different systems (easy to see at low power). My reading of it is 
> that a streamer issues from the terminal and a close enough object
> (either simultaneously or when the terminal leader gets close enough 
> to the target (cf. lightning)) and the two meet in the middle where, 
> presumably, the highest concentration of energy is. Any 
> advance/correction to this anyone?
> Malcolm 

This sounds very reasonable. Bazelyan in "Spark Discharge" describes just
such a proposed mechanism. That is, a leader proceeds from the electrode
with the higher field (i.e. the smaller one), until it is within a certain
distance of the other electrode. The final few cm is jumped both directions
simultaneously. On a 10 foot spark, this last phase (arc completion), isn't
a very big fraction of the whole. But, if it were of fixed size, then for a
very short spark, as you describe, it might be a bigger fraction.

Also, have you contemplated the impact of the fact that a Tesla coil is AC,
and that you mgiht actually be seeing sparks going both directions, on
alternate half cycles. Your vision superposes the two leaders, each of
which is less than the whole distance.

I have noticed a phenomenon with my Van deGraaf generator that the sparks
are divided into two parts, a bright part and a thin part, always the same
orientation relative to the polarity of the discharge.  This might be
because of the phenomenon of limited stored energy, where the leader
extends, then collapses back into the electrode.