The electrons that fall in along the boundary between these sections form rings in the upper atmosphere as they fall toward the poles, giving rise to the aurora's halo-like appearance. Here we see a bar magnet and a ring magnet. This is the Laboratory Aurora Display Device . At the top of a vacuum tank, a plug is attached containing a tapered electrode and an air outlet. A powerful magnet is placed at the bottom of the tank, capped with a model of the conductive hemisphere.
Voltage is applied to the vacuum tank, and the air is evacuated.
We'll start the experiment using a ring magnet, then switch to a bar magnet, and compare the forms of the aurorae generated over the hemisphere. With the bar magnet, however, no such ring appears.