Tom:

Unless I miss my bet, it seems you are referring to what looks like wire
embedded in the top of the canopy, but is really small diameter detonation
cord (det cord) and it is used as one of the first events in an ejection
sequence.

In the type I am describing, the transparent canopy is shattered by the
explosive in the det cord, the slipstream carries away all the small bits of
plexiglass and the ejection seat containing the pilot follows a few
microseconds later. In some types, the whole canopy is blown clear of the
aircraft before the seat goes. An example of this can be seen in the
picture of the ASAF Thunderbirds F-16 ejection at
http://www.ejectionsite.com/ a search on ejection seats might make for some
interesting reading.

Hopefully, I'm not leading you on a wild goose chase.

Regards,
Lee