A terrella (meaning "little earth") is a small magnetised model ball representing the Earth, that is thought to have been invented by Englishman physician William Gilbert while investigating magnetism, and further developed 300 years later by the Norwegian scientist and explorer Kristian Birkeland, while investigating the aurora.
North and South Pole magnets are not only holding together the earth and moon, but they are turning the earth around on its axis. Those magnets which are coming down from the sun they are hitting their own kind of magnets which are circulating around the earth and they hit more on the East side than on the West side, and that is what makes the earth turn around.
The earth itself is a great big magnet. In general these North and South Pole individual magnets are circulating in the same way as in the permanent magnet metal."ED.L"
Terrellas had been used up until the late 20th century to attempt to simulate the Earth's magnetosphere, but have now been replaced by computer simulation.
Source : Wikipedia
Kristian Birkeland and his terrella experiment.