Hi.  Just curious...I have seen many jet fighter canopy with some sort of wire frame at the (inside) top of the canopy.  See AV-8 Harrier or T-45 canopy.  What is this wire frame for?  Thanks.

The wire is actually a detonation chord.  During the ejection sequence, the chord fractures the canopy allowing the pilot to safely eject through it.  Some jets, like the F-16, don't have detonation chords and have to blow the canopy completely off first before the seat can safely eject from the aircraft.