Re: Speed of Streamer formation

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Jim, Dave, and all,

There's some evidence that the next leader follows the same channel as
the previous from bang to bang  due to residual hot air left in the
previous leader's channel. While the channel air temperature is much too
low, and duration too long, to convincingly explain consecutive
breakdown on the next bang from  residual ions, residual channel heat
may simply make the air in the former channel less dense. Since less
dense air has a lower breakdown voltage than the surrounding colder air,
the next leader finds this path the "weakest link", and the next leader
preferentially follows the "warm" path blazed by the previous leader.

Best regards,

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<davep-at-quik-dot-com>
> 
> Tesla list wrote:
> >
> > Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <jimlux-at-earthlink-dot-net>
> 
> > > I suggest that gradual growth of streamer length may be due
> > > to increasing number of ions present in the immediate
> > > vicinity.  Recombination (and air mixing) take a finite
> > > period of time...
> 
> > The "burning" question.. how long?
> 
>         Dunno.
>         I Assume the answer is out there, at least for some gases
>         at some temperatures....
> 
> > Clearly, it's not just the cooling of the plasma until it stops
> > conducting (which happens VERY fast, considering that there's a
> > pretty sharp knee in the conductivity vs temp curve).
> 
> > Although, the radiation cooling (probably dominant?) does go as T^4,
> > so it might stay pretty hot, but not radiant (at least in visible..).
> > Hmmm..
> 
>         Indeed.  I suggest the issue is electrons dropping back down
>         the orbital levels, which can be cooling, per se, or other
>         factors.  (Note that lifetime of 'population inversion'
>         (electrons in high orbitals) is critical to laser function.)
>         More so: the ions involve electrons physically separated from
>         atoms.  They need to travel home.  This CAN happen quickly,
>         or slowly (milliseconds, longer) depending on pressure, gas, etc.
> 
> > This is an area that isn't covered by much of the spark literature.....
> 
>         I'd look into physics work on conduction in gases: Cobine, Gaseous
>         Conductors.