[maquiladora]

Would energized plasma have a radar signature?

I admit, this is a weird one. The last big UFO thing I recall was the Pheonix lights back in 1997 or 98 I think it was. But I think that turned out to be an array of flares or something.

[Hellmouth]

I don't know, just speculating that it might be something anomalous/unknown. Remember the hubbub about the sprites?
Perhaps it's a low atmosphere version of a sprite. It might be a missile - but don't missiles either go boom or crash to the ground and leave debris? So, that would seem to rule out the missile hypothesis.

[carenot]

But I think that turned out to be an array of flares or something.

Yup, just citizens shooting off flares or something.