i think the presence of aurora bureallis is one of the proofs? because if the earth is flat then there is no north and south pole that have magnetic interactions with one another to produce the said phenomenon.
The aurora borealis and Earth's magnetic field are not exclusive to the globe.
The globe theory says that a molten nickel-iron core @ 5,430 °C creates the magnetic field. However iron loses it magnetic properties when it passes the curie temperature @ 770 °C and nickel @ 354 °C.
In reality the dome or firmament that covers the plain of the earth is made of sold nickel-iron steel that's electrified to an extreme potential. The positive electrical charge of the dome induces a negative charge on the Earth below and a magnetic field (Earth's magnetic field) at 90°. The result is a magnetic field with its north pole at the center and the south pole around the circumference of the plain, the same configuration as in an audio speaker magnet.