What I'm thinking of is not a plasma globe, although, like the globe, it
too is intended primary for display. If I were to describe it, I
remember it being made out of glass, maybe 1-2 feet in diameter, and
nearly flat in thickness. Electric discharges from the center to the
edge of the glass and looked a lot like lightning. I remember these
devices being used in Star Trek The Next Generation used behind the
heads of Borg drones. They used to be in Spencers too available for
purchase.