This artwork turned out just like the glow in a plasma globe. It wasn't intended, but art sometimes has an opinion of its own.
Plasma balls glow as a result of the high voltage running inside a noble gas. It causes what is known as corona discharge that might be seen on high-voltage power grids.
Oh, and by the way, ozone generators also employ high voltage in the same manner, however, probably you don't want to risk putting your fingers anywhere near 10 kilovolts.