Earth’s Magnetic Field: Origins
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The largest magnet in the world is the world. We take it for granted, but the Earth’s magnetic field is a dynamic force that plays a crucial role in maintaining life on Earth. I’m Jim Metzner, and this is the Pulse of the Planet. Gary Glatzmaier is a Professor at University of California Santa Cruz.
“It’s interesting that we live our entire life in the Earth’s magnetic field, and yet most of us don’t think about it very much. We don’t sense it, but it helps shield us from cosmic radiation: high-energy, fast-moving particles, mainly coming from the Sun. Particles get shot out towards the Earth, and instead of hitting the surface of the Earth directly, the magnetic field tends to deflect them and they get focused on geographic poles, where not many people live.”
So what generates Earth’s magnetic field?
“Now, the core of the Earth, the center core, is actually solid, and then there’s a liquid outer core above that. So, what’s happening is the Earth is cooling off – heat builds up, and the fluid expands a little bit and becomes buoyant. It weighs a little bit less than the fluid around it, and so it starts to rise. And this rising metallic fluid causes large electric currents to be generated. And whenever you have a new electric current, there’s a new magnetic field circling around it. So, for many years, people have had this sort of ‘back of the envelope’ idea that this type of fluid motion in the core of the Earth, is somehow generating the Earth’s magnetic field, but why does the field slowly change – even within ten years?”
In future programs we’ll find out why the intensity and direction of Earth’s magnetic field has changed dramatically over time.
Pulse of the Planet is made possible by the National Science Foundation. I’m Jim Metzner.