Re: Streamers

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

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

Bert: I like your posting and I intent to save it, but...I have measured ion
life in liquids over 11 seconds and in air over several minutes. While the
center ion track time is limited to the browian movement time the surounding
wide track remains for a long time like a static cloud.
  Robert  H 

> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Sun, 24 Feb 2002 22:26:39 -0700
> To: tesla-at-pupman-dot-com
> Subject: Re: Streamers
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Sun, 24 Feb 2002 22:36:49 -0700
> 
> Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <bert.hickman-at-aquila-dot-net>
> 
> Dave and all,
> 
> I still suspect the main reason why leaders follow the previous channel
> from bang to bang is lower air density and not the presence of residual
> ions. The reason? Although longer lived positive and negative ions can
> indeed persist from one bang to the next, their presence does not
> directly contribute to the spark breakdown process on the next bang.
> 
> Avalanche breakdown initially requires free electrons, accelerated by an
> E-field, colliding with air molecules, to create an increasing cascading
> shower of free electrons. For the avalanche to proceed, the rate of free
> electron creation must exceed the rate of electron loss through
> attachment (to oxygen or water vapor molecules to form negative ions).
> Electron attachment occurs very quickly in air. Any free electrons
> created during the previous bang are long gone by the time of the next
> bang, having been captured by electronegative gases in the air since the
> average "free" electron life in air at STP is only about 11 nSec.
> 
> It is possible to "detach" some free electrons from negative ions via
> thermal collisions with other molecules. This process requires fairly
> high temperatures (>1,000 K), but is it possible that detachment
> provides some free electrons. It's likely more fundamentally that the
> spark channel used by the previous leader leaves behind a "tube" of
> significantly less dense (lower pressure) air which has not had the
> opportunity to dissipate into the cooler surrounding air. Within this
> lower density tube, the mean free path of new seed electrons (from
> cosmic ray, background radiation, or electron detachment) is longer,
> allowing the electrons to gain more kinetic energy from the E-Field
> between collisions, increasing the probability of ionizing collisions
> and avalanche multiplication. In this manner, the hotter "echo" of the
> previous spark channel most likely becomes the preferred region for
> avalanche breakdown during the NEXT bang.
> 
> The presence of residual ions in the region may be mostly of scientific
> interest, since these ions don't appear to have as much of a role in
> avalanche breakdown during a subsequent bang as the lower air
> pressure.     
> 
> 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:
>> 
>>> Jim, Dave, and all,
>> 
>>> There's some evidence that the next leader follows the same channel as
>>> the previous from bang to bang
>> 
>> This is well documented in 'natural' lighting.  I can't think
>> Tesla Coils streamers, with shorter lengths and arguably
>> faster 'refresh' would different.
>> 
>>> 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,
>> 
>> My understanding of the lighting, and other, data differs.
>> Ions can have surprisingly long lifetimes.
>> 
>>> 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,
>> 
>> Be it ions or 'temperature':
>> 
>>> the next leader finds this path the "weakest link", and the next leader
>>> preferentially follows the "warm" path blazed by the previous leader.
>> 
>> Concur...
>> 
>> Or one near by (eg the invisible ion (or heat) trail gets drifted
>> about by normal air movement, and...
>> 
>> best
>> dwp
> 
> 
>