Re: Statistics & spark length and Air Pressure

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

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 08:27 AM 6/10/2003 -0600, you wrote:
>Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><dhmccauley-at-spacecatlighting-dot-com>
>
>The dielectric of air varies (increases) with increased air pressure.
>However, I am thinking this characteristic would mostly apply only to
>pre-breakout conditions.
>I think once that the air is sufficently ionized by previous streamers, that
>spark length vs. altitude would somewhat normalize and that air pressure
>would be less of a factor.
>
>Any thoughts?

  I think that the spark growth, though, is always occurring in 
"undisturbed" air, with the previously ionized channel providing a "wire" 
to the end of the channel.  Therefore, the reduced pressure would help...

I agree though, that once the air is hot/ionized, the effects of altitude 
are less important.  Something that just occurred to me is that while the 
ions recombine fairly quickly, the hot air left behind is that much easier 
to ionize.  The entire air mass (previously hot channel and surrounding 
air) is probably all at the same pressure: figuring a few milliseconds 
between successive bangs, there's plenty of time for it to reach pressure 
equilibrium on the scale of centimeters(speed of sound -at- 300m/sec and all 
that).  However, the density of the air in the hot channel will be less 
(and have a lower breakdown field when the next bang comes along), and, 
because it's hot, it takes less energy to get it up to the 7000K or so for 
a plasma channel.



> > >Finally, remember the spark length depends on air density. It would be
> > >unfair to compare, say, Terry Fritz's efforts in the thin high-altitude
>air
> > >of Colorado, with Captain Corona in New Jersey. Where does John Freau
>live?
> > >
> > >Steve C.
> > >
> > >