In Walter Lewin's 8.02 Electricity and Magnetism course, he places a fluorescent tube pointing radially outwards from a large Van de Graaff (VDG) generator. Due to the VDG's E-field, this causes a large potential difference between both ends of the tube. He then says that this high voltage causes a current in the tube, which creates light.
Subsequently, he then touches the end of the tube furthest the VDG, receives a shock, and by grounding this end, allows more current to pass, thus creating more light.
If the tube is not in a circuit, that must mean all the charges that were moved by the potential difference are accumulating in one end of the tube, causing the tube to act like a capacitor and eventually stopping current flow. Obviously this is not what is happening because the tube creates light continuously.
So what exactly is the path of the current, and why should the tube light up more if Dr. Lewin grounds one end through his body?
EDIT: He also does this experiment with a neon flash tube, and it creates light as well