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Re: spark shape observation


From:	Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:	Wednesday, November 12, 1997 3:18 AM
To:	Tesla List
Subject:	Re: spark shape observation

Tesla List wrote:
> 
> From:   kevin [SMTP:wawa-at-spectra-dot-net]
> Sent:   Tuesday, November 11, 1997 6:14 PM
> To:     tesla-at-pupman-dot-com
> Subject:        spark shape observation
> 
> Previously, I have been using unsmooth forms for my coil (ie. foil
> covered ball, aluminum ducting).  With this setup I get sparks from all
> the sharp points.  A week or so ago, I got a Van De Graff from a friend,
> with a smooth aluminum sphere.  That found its way right to the top of
> my tesla coil.  Now when running, i get a few longer sparks that move
> all over the sphere.  It's really great.  Any way I noticed something
> I've never seen before.  Usually, the sparks are very jittery and break
> apart and are all fragmented.  But occasionally, the spark just
> straigtens right out so that it is one great long one.  It just seems to
> stay in one place and it looks like it is flowing like water or
> something.  Then after up to 6 or so seconds, it breaks off into what
> I'd say is normal operation.  This seems very strange and intersting to
> me.  Has anyone else ever noticed this?  I've never read anything on
> this adn was wondering if someone could possibly explain it to me.  It
> seems to me like it could be something important.
> 
> Thanks
> kevin Wahila

Kevin,

This is characteristic of a spherical TC terminal. Under the right
(still air) circumstances, the heating of the air due to the streamer
discharge creates a consistently weakenned/ionized path that stays in
one place for a considerable period of time. Since the hottest portion
of the streamer is at the base of the streamer, the hot, ionized air
rises, making the path immediately above more conductive. This path can
remain stable for a relatively long time, in the process creating a
longer than usual total discharge length as well.  Nice observation!

Safe coilin' to you, Kevin!

-- Bert --