Why is the earth's magnetic field important?

What has the earth's magnetic field ever done for us? Chris Smith put this to Kathy Whaler from the University of Edinburgh. First off, Chris asked Kathy what shape the field is...

Kathy - Well interestingly, the shape is very much like a bar magnet as we’ve just been hearing with two poles - a north pole and a south pole. And because the convection, the liquid is moving around so strongly influenced by the Earth’s rotation, that bar magnet field lines up with the north-south poles approximately. So it does look very much like a bar magnet but it’s caused by a very different mechanism.

Chris - What benefits does the field impart to us as dwellers on Earth?

Kathy - Well, we’ve already heard about it shielding us from the vagaries of space weather so it stops solar charged particles reaching the Earth’s surface for most of the part. It gives us a way to navigate as you were saying at the start of this programme. It imparts a signature to the geology which we’ve found helpful in exploration for resources. And it really is our protective shield and that’s perhaps the most important thing about it.

Chris - And in protecting us that also gives us that lovely light show that we call the Aurorae?

Kathy - That’s right.

Izzie - Why is it so important to study it and what can it tell us?

Kathy - Well, it does provide our window on the core, so a lot of the information that we have about the Earth’s core has come from knowing its magnetic field and knowing how that field changes over time. We can also use it investigate the geology; we can look for mineral resources; we can look for hydrocarbon resources  - it’s used to help when we’re drilling for those resources. We can even see a magnetic field in the oceans when we’re looking at the data collected by low Earth orbiting satellites. So because the oceans are a salty water, as they move around they also generate a magnetic field in a rather similar way to the Earth’s core itself. And we can see the ocean tides even.