Short term: Pain and Zero Gravity
This lightbulb would keep heating your sphere. How would heat escape. Heat flows from hot to cold. As long as the molten outside layer is hotter than the inside, the layer with humans will get extremely hot. The only form of cooling will be radiation, but it will be slow because the outside layer will absorb it. Also, the outside layer will not cool quickly due to radioactive decay. There are radioactive isotopes in the earth's mantle. There decay will continue to heat the mantle and to bake us alive. We would either be weightless or we would have to stand on the lightbulb, depending on how massive you have made your lightbulb. This is due to Newton's Shell Theorem. It says that in a hollow sphere, gravity cancels out, making the inside experience zero gees.
Short term: Death
The heat on the inside would bake the earth. Everyone dies. Your aliens turned the earth into an oven.