@Jess👾 It's probably not induction. A while back there was a light bulb company that had an advertisement where they would unscrew the light bulb from the lamp socket and it would keep glowing, and to further the effectiveness of those advertisements they added some glow in the dark phosphors to their bulbs so they would glow for some time after being turned off. But, if you want to test for inductance, just place it in a Faraday shield, such as a microwave oven (don't turn the oven ON while the bulb is inside if you don't want flaming / melted bulb remains). If the glow goes out while inside the Faraday cage, then OK inductance, but unlikely unless you live next to a higher powered radio or television station.