Re: stepped leaders

Tesla List wrote:
> >From rwstephens-at-ptbo.igs-dot-netMon Aug 19 21:51:26 1996
> Date: Mon, 19 Aug 1996 14:14:20 -0500
> From: "Robert W. Stephens" <rwstephens-at-ptbo.igs-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: stepped leaders
> >>From hullr-at-whitlock-dot-comFri Aug 16 13:38:33 1996
> >Date: Fri, 16 Aug 1996 11:04:25 -0700
> >From: Richard Hull <hullr-at-whitlock-dot-com>
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Safety FAQ is here -- draft, asking for comments.

magnum snip....

> Richard H., Malcolm W., Greg L., Bert H., Brent T., Steve R, Skip G.,  All,
> This has become quite popular and I wish to address all of you in
> general to save some time.  Does anyone remember that Skip started
> all this? :)
> In my original post I achnowledged the long time existence of an
> ionized path remaining in place after the light (energy) dissipated
> from the previous arc.  I didn't have a handle on the timeframe of
> the existence of such lingering ionization.  Richard Hull has helped
> put it in perspective.  I am certainly suprised to learn that pulsed
> streamers created with less than a full capacitor charge along the
> charging sine wave reach out just as long as the full charge
> streamers, just less luminous.
> I am certainly finding this exchange interesting and educational.  I
> do wish to say however that no one has yet given me evidence of
> succeeding streamers 'building' upon their immediate forerunners.  The
> forerunners are gone by the time the next streamer comes along.  Yes,
> there is an ionization pathway that helps successive streamers to
> propagate, but I think maybe the definition of 'building upon
> preceeding streamers' is fuzzy or misleading, or subject to
> interpretation.
> As I see it there may be two major interpretations.  Mine is: "O.K.
> you've got a streamer (ionized, light emitting arc channel), next
> you've got the same arc channel but it has suddenly grown in length
> by some increment, then maybe again something happens and this arc
> channel is suddenly longer again, its light output has not ceased at
> any time during this cascade of growth".  That is MY definition of a
> streamer building upon itself.  Some of you out there may define a new
> streamer heading out along a non luminous ionization highway paved by
> a previous streamer as 'a streamer building upon itself'.  I ACHNOWLEDGE
> THIS EFFECT, but do not support the definition.
> Malcolm's comment that single shot coil experiments come no where
> near to the streamer length achieved at regular system break speeds
> certainly shows that the existence of this ionized spark highway make
> succeeding pulsed streamers using that particular highway more
> successful in the length business.  No argument here!  Bert, your
> post went into the mechanics of this in excellent detail, and I agree
> with much of what you said, but not the 'stepped leader' label.
> Greg Leyh has also just suggested that we might compare
> this effect to the stepped leader phenomenon found in nature's lightning
> whereby the propagating , advancing arc channel actually stops and
> pools energy for some 50 or so microseconds before leaping 50 or so yards
> and then stopping and pooling again.  I responded to his post suggesting that it
> is not reasonable to draw this parallel.  If a Tesla coil discharge
> acted this way, we would see a streamer reach out, then while it was
> still emitting light, the system break would add another energy
> pulse, and we would see our existing streamer, make a jump in extra
> length, the process continuing until a balance was achieved between
> the system power and the loss load on the streamer.  Perhaps this
> would be observable with a system operating at ultrasonic break
> rates, but I certainly haven't see it a modest typical rates of
> 400 PPS.  And, if this WAS occuring,  Richard Hulls  'banjo effect',
> when the wind blows the arc channel sideways, would only be
> observable at the outward ends of the streamer, not over
> its entire length.
> Please excuse me if I appear to be dragging this thread too far.
> Richard's and Malcolm's most recent posts attempting to explain the
> cause for a long time (relatively) connected super-hot streamer to
> suddenly disconnect and look for other targets is certainly another
> related phenomenon worthy of research and explanation.
> Comments, flames, welcome.
> Regards, rwstephens


I just read this after posting a similar response to one of Skip's posts

  I agree with the stepped leader business.  It just doesn't play well 
here either.  The sparks grow along the ionized path of previous sparks; 
each from a single spark gap pulse.  The reduced impedance of the air 
remaining from a previous pop, just acts like a length of moderate 
resistance wire growing out from the toroid.  To keep lengthing this 
wire, energy must be put into the old path, maintianing existing 
ionization.  Any energy left over, reaches a bit beyond.  The process 
continues until there is only enough energy is succesive pops to barely 
maintain the last existing channel.  This is the "rope limit" (referring 
to the dog's tether in old Foghorn Leghorn W.B. cartoons).  Beyond this 
more energy is required, not more voltage!  (although voltage helps too.)

Richard Hull, TCBOR