Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!husc6!cca!g-rh
From: g-rh@cca.CCA.COM (Richard Harter)
Newsgroups: sci.misc
Subject: Re: Lightning, Up or Down?
Message-ID: <25074@cca.CCA.COM>
Date: 29 Feb 88 06:24:23 GMT
References: <64600001@mic> <512@dukempd.UUCP>
Reply-To: g-rh@CCA.CCA.COM.UUCP (Richard Harter)
Organization: Computer Corp. of America, Cambridge, MA
Lines: 41
Summary: Yes.

In article <512@dukempd.UUCP> crown@dukempd.UUCP (Rick Crownover) writes:
>In article <64600001@mic>, gary@mic.UUCP writes:
>> 
>> Is it correct that lightning travels from the ground up instead of the
>> sky down to the ground?  I vaguely remember that this is the case but
>> do not remember where I read about it.
>> 
>	Lightning can strike upwards in one sense: in the mountains, it is
>possible to see lightning originating in an air mass below the ground it strikesThere is a description of this phenom in Goethe's "Faust" in the Walpurgis
>scene.  I doubt that lightning strikes from ground to sky for two reasons, 1)
>the slow motion films I've seen always show it going the other way, and 2) the
>ground is conductive and would have trouble building up a large local charge.
>But, I'm with you, does anyone know?

This may be unfair, but I took the liberty of looking up lightning in the
Enc. Brit. I quote:

"A faint luminous process in regular disinct steps, typically of 50-metre
length, at time intervals of 50 microseconds, descends in a downward
branching pattern toward the ground.  Carrying currents on the order of 
hundreds of amperes, this stepped leader or initial stroke propogates
at a typical velocity of 1.5E5 metres per second, or about one two-
thousandth the speed of light... As the branching process nears the
ground, approximately five coulombs of charge have been induced on the
channel, inducing an opposite charge on the ground and increasing the
electric field between the lead and the point to be struck.  An upward
discharge occurs from the ground, church steeple, house, or other object
to meet the stepped leader about 50 metres above the surface.  At this
moment of junction the cloud is short circuited to the ground and a
highly luminous return stroke of high current occurs."

In conclusion, the original question is not well posed, because it assumes
that there is a single direction of lightning stroke, whereas in fact
there are two processes involved, one downwards and one upwards.  However
the highly luminous return stroke, which we see, is upwards.

Ref Enc. Brit., 15th edition, vol 10 of the macropedia, pp 965-970.
-- 

In the fields of Hell where the grass grows high
Are the graves of dreams allowed to die.
	Richard Harter, SMDS  Inc.