MAGNETISM

Happy New Year! I’m Marley, the astronomer here at the Space Centre. For January and February, our special events will centre on the idea of magnetism. When you think about magnetism, you probably first think about a physical magnet like one you would put on your fridge, or maybe the North and South Poles of Earth. Here, we will dive more into the role of magnetic fields in space! Magnetic fields of some sort are everywhere, and Earth’s originates deep in the interior of our planet.

We can think of the solid parts of Earth as an onion. There are four major layers: the crust, the mantle, the outer core, and the inner core. The outer core is made up of molten iron and nickel, both of which conduct electricity. The outer core is where the magnetic field originates. The liquid of the outer core sits above an incredibly hot inner core, which sits at about 6000K at its hottest. This causes the outer core to heat up. Hotter materials rise, and cool before falling back down. This movement, along with the rotation of the Earth, generates electrical currents which leads to the creation of our magnetic field. The magnetic field is shaped similarly to a bar magnet. There is a north and south magnetic pole, and the field lines move out and around from the north magnetic pole, and reenter at the south magnetic pole.

Earth’s magnetic field, or its magnetosphere, acts as a barrier. It shields life below from harmful radiation from solar and cosmic particles. It also stops the atmosphere from being eroded from the constant stream of charged particles coming from the Sun. However, some of these electrically charged particles manage to come through our magnetosphere. They get caught in the magnetic field, and funneled towards the poles. Once they reach our atmosphere, they collide with the gases found there. This creates the beautiful aurora borealis and the aurora australis. During periods of intense solar activity, the possibility for stronger aurora increased, which you can read more about in our blog about the solar cycle.

The Earth is not the only planet with a magnetic field. Mercury has a very weak magnetic field, and Mars had one in the past. Earth is not even the only planet that gets auroras! Astronomers have found aurorae on all the outer planets, though they are slightly different from the aurorae we see on Earth. For example, while Earth’s aurorae only occur during times of increased solar activity, the aurorae on Jupiter are permanent.

Jupiter’s magnetic field is caused by liquid metallic hydrogen in its outer core, and the field interacts heavily with the Galilean Moons that orbit Jupiter. The consistent aurorae are caused by the volcanic eruptions on Io. The eruptions produce large amounts of sulfur dioxide gas into space, which gets swept up in Jupiter’s magnetic field. The result is a near constant amount of material funneled towards Jupiter’s poles, creating aurorae in radio, infrared, and x-ray wavelengths.

Magnetism is everywhere we look in our Universe. Not only is it essential for life as we understand it on our planet, it is responsible for some of the most spectacular views on the planets across our solar system. If you’re interested more about magnetism, feel free to check out some activities below