More on spark delay

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Kchdlh-at-aol-dot-com>

I've put forth my hypothesis more than once that the relatively high
rate-of-rise of spark-gap-coil voltage is the reason that spark-gap sparks are
longer than SSTC sparks.  I've proposed that that high rate allows the toroid
voltage to rise higher during the time it takes for the spark to propagate. 
That time period exists due to the necessity to heat and displace the air along
the spark's path.

The notion has received scant attention.  I may be repeating myself but here's
an observation I just made today:   In my SSTC, the toroid voltage's rise &
fall is extremely stable from spark to spark.  So, I can sync the scope to it
and accurately gauge the rise and fall.  I find, at commencement of the spark,
that the toroid voltage falls abruptly, at first, to about 70% of the level
that it holds during the remaining 5 milliseconds of the spark's duration. 
That fall seems to take place well within 1 cycle of the excitation, which is
at ~140 KHz , and it always occurs at a negative half-cycle (indicating to me
that the spark initiates when the toroid is 'crowded" with electrons and not
otherwise).  It then takes just about 100 microseconds longer for the voltage
to decline further to the steady level.

Clearly, at the instant of the 30% drop, the impedance of the initial spark has
appeared in parallel with the impedance of the capacitance between the toroid
and ground.  But at the end of that instant, the spark impedance is still
relatively high since its presence in the series circuit of
ground/secondary/toroid:ground capacitance/ground (across "toroid:ground
capacitance") has diminished the toroid voltage by only that 30%.  The spark
impedance then relatively-slowly decreases during the following 100 us, causing
the toroid voltage to correspondingly diminish.

So my supposition remains:  It is the capability of spark-gap systems to
deliver higher power during the (at least first part of) 100 us or so that
allows for the longer sparks.  And it is the physical/thermal inertia of the
air in the path of the spark that causes the 100-us phenomenon to exist.

But perhaps this is old-hat to spark experts.  Comments?...

Ken Herrick