We live in the Earth’s magnetic field 24/7 and at times, its effects become visible. Migratory birds and turtles are known to use the Earth’s magnetic field to navigate long distances. But did you know the Aurora Australis, the southern lights and Aurora Borealis, the northern lights are a phenomena caused by the Earth’s magnetic field?
Auror Australis. Fish Creek, Victoria. Image © by Andrew Wallace
The coriolis effect generates currents of iron rich molten rock in the spinning Earth’s core, producing a geomagnetic dynamo. This induces a giant magnet, which in turn creates the magnetosphere. Similar in a way to the atmosphere which surrounds the Earth, except the magnetosphere projects millions of km out into space.
SHIELDS UP Earth’s magnetic field. Image © by NASA
Large Solar flares cause magnetic storms, that eject masses of highly energetic particles, like electrons.
Auror Australis, looking south from Melbourne. May, 2024. Image © by Andrew Wallace
These accelerated electrons follow the magnetosphere’s field lines to the north and south magnetic poles and “excite” the atmospheric gasses, such as oxygen and nitrogen, which produces the different colours of the aurora.
Not many people are aware, but the Earth’s magnetic field is quadrupolar by nature. See example below from NOAA. The north and south magnetic poles do dominate the weaker quadrupoles and hence when commonly illustrated, you only see the north and south magnetic poles. But the extra poles do exist in the background.
Image courtesy NOAA. https://www.ncei.noaa.gov/products/world-magnetic-model
