Subject:      Re: Ball Lightning
From:         dmsmith@io.com (Dan and May Beth Smith)
Date:         1995/11/15
Newsgroups:   sci.physics


In article <9511110016.AA003c2@folkmus.demon.co.uk>, Dr John Barrow
<jb@folkmus.demon.co.uk> wrote:

> Robert Macy (robert.macy@engineers.com) wrote:
> : How is ball lightning made?
>
> Don't know, but recently on Channel 4 (UK) TV they TX a repeat in the
> excellent Equinox series (this Sunday's is about avalanches and the trailer
> footage looked V spectacular) of a film about atmospheric electricity.  A
> researcher somewhere in the USA made mini-*ball lighting* by (I think)
> vapourising metal.  The intense small ball ran across a liquid surface.  He
> simply discharged a large spark across a gap it seemed.  I think the
> commentary gave the impression that this was as near as anyone has got to
> creating the phenomenon.
>
> : Is it plasma (ionized air)?
>
> If this chap was producing ball-lightning or something similar, it didn't
> look like ionized air.  But, in other incarnations of which I have read, the
> phenomenon seemed to be viewed that way.  A mention appeared in the IoP
> journal, Physics World 2-3 years back, maybe more, in which it said that
> ball lightning had been seen to enter the fuselage of a passenger aircraft
> in flight, had moved slowly down the aisle to the back of the plane and had
> exitted at the rear (and I don't think this was April 1!!).  If this was
> true ionised air sounds plausible maybe.
>
> : Why is it stable enough to exist for measurable times?
>
> Don't know
>
> : Is there a "minimum" size requirement?
>
> Don't know
>
>
> John Barrow
> :-)

     A very extensive survey of ball lightning observations and theories
was published by Powell and Finkelstein in the May-June 1970 issue of The
American Scientist.
     Powell and Finkelstein propound a theory of ball lightning in which
the ball is NOT a plasma but rather is a heated volume of
"electroluminescent" air sustained by an intense "poststroke" terrestrial
electric field, of the order of 2,000 volts/cm, in which Townsend avalanche
multiplication of electrons and ions is the source of light. Powell and
Finkelstein believe that their model can explain the passage of a ball of
lightning through a glass window, as a dissipation and subsequent
re-formation of the ball on the other side of the glass.
     It seems to me that "ball lightning" made by discharging submarine
batteries across a metal to metal gap, as shown in The Learning Channel's
program "Electric Skies" is not ball lightning in Powell and Finkelstein's
sense, as it is a strictly low voltage phenomenon.
Regards,
Dan Smith