If I remember correctly,

Lightning takes place in two steps. First, the negative body (usually the ground I believe) sends a thin, generally invisible streamer of electrons towards the positive body (a cloud). A conductive path then exists. Next, an intensely hot, bright plasma consisting of ions, free electrons, atoms, and air molecules develops along that path. That plasma allows electrical charge to be exchanged between the cloud and the ground. The jagged shape of the lighting bolt has to do with how that original electron path is created. The explanation is fairly technical.

I suspect that the blue jet phenomenon discussed in that report represent the opposite type of process. In that case the negative body would be the upper atmosphere.

Regarding low temperature nuclear fusion, acetone contains carbon, hydrogen, and oxygen. The phenomenon those researchers are observing when they send sound waves into that chemical might represent a type of combustion where the atoms rearrange themselves into different configurations. New chemicals would be temporarily or permanently created. Or, a several step process might be converting sound energy into heat energy in the reaction vessel. I cannot imagine that hydrogen fusion would take place under such relatively low temperature conditions. And I would also like to be wrong about that. We could use a good source of energy such as low temperature nuclear fusion.