Well, the top of the field is near the North Pole and that’s why all magnets point north.
A planet’s magnetic field forms a shield, protecting its surface from tiny energetic charged particles coming from the Sun and other places.
The Sun is constantly sending these particles out. They’re called solar wind but when they hit a magnetic field, they’re deflected.
You can see the effect for yourself…
Northern Lights
You may have heard of Aurora Borealis in Norway – better known as the Northern Lights.
These shimmering light displays are made by particles from the solar wind hitting the molecules high up in Earth’s atmosphere.
Sometimes they look like waves, other times like spikes, and they come in all sorts of colours.
If a planet doesn’t have a magnetic field then magnetic activity can’t take place.
The biggest benefit of magnetism is life on a planet. Solar wind damages living things you see.
Remember, the core of the planet is the cause for a magnetic field!
Deep inside the Earth’s core, hot iron flows generate an electrical current, and this in turn generates magnetism.
So if a planet has a magnetic field, we know it has a moving iron core!
It’s tricky though because it has to be hot enough, big enough and flowing enough to create a magnetic field.
The flow is faster if a planet is spinning more quickly. Slow planets don’t build up enough speed for their own shield!
Venus doesn’t have a magnetic field even though we know it’s got a warm core – it’s just too slow. In fact, one day on Venus is almost over 200 days on earth!
Mars is another planet that has a very weak magnetic field. It’s spinning fast enough, but its core is thought to be solid.
Jupiter though has a huge magnetic field, not least because of its size and it spins super fast, one day is just 10 hours!