I didn't see that one. Is it the one with the stratospheric bolt
allegedly hitting the shuttle and the glider getting hammered?

Ionospheric TS charging has been postulated for a long time as charge
seperation by ice crystals rubbing against each other in an updraught
isn't enough. I had a 1969 "Practical Electronics" which the author, MA
Michaelis, thoerised that the ionosphere had something to do with it, or
at least some of it. Now lost since I moved here, there was a brilliant
electrostatic field meter too if i remember correctly.

This cannot be the only mechanism that produces lightning we've all
encountered the flash - bang - gone single single cells of shallow
vertical extent that gets nowhere nere the trop!

The ionosphere sits at around +225kv positive to ground at midday local
in fair weather and is the basis for terra's electrostatic field
measurements.

This isn't enough for a direct spark to ground else we'd all be getting
fried by superbolts on a regular basis but the cloud is going to modify
the field somewhat.

Stillings had a cracking +CG photograph originating from the anvil of a
ts - and extending miles away from the cloud - on his website and the
BBC had a few up that looked suspiciously like +CG superbolts too (the
broad channel is a giveaway as is the bolt not coming out of the cloud
base).


I'll have to get that cokebottle magnetometer or field mill built.
Plenty very powerful magnets available these days (dead hard disks!) and
using a laser pointer with a mirror and a webcam could give a very
pretty picture (:


Les

Dave Liquorice wrote:
On Tue, 28 Jun 2005 13:43:00 GMT, flybywire wrote:


lightning, red sprites, blue jets, and elves.


Quite an interesting prog on five(?) "Megalighting" last week covering
sprites and jets. Trying to pin the 2nd space shuttle crash onto
lightening, officially it was wing damage from foam off the external
tank but...

This shuttle stuff formed only a small part of the programme most was
about the discovery of sprites and latterly jets. And the link beteen
sprites and positive cloud to ground lighting. Appears that a sprite
channels energy right from a vast area of the very high atmosphere to
ground in a +ve CG strike. These strikes are tremendously powerful,
much more so than "ordinary" lighting. Stroke durations measured in
100's of mS rather than around 10mS.


--
Les Crossan,
Wallsend, Tyne & Wear
54.95N 1.5W
Home of the Wallsend StormCam and the Backup USW FAQ -
www.uksevereweather.org.uk