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I'm a space physicist. I've been working with a group of school students (aged between around 10 and 12) exploring the Sun, the Earth and the solar system. We've talked about some basics of magnetism and the fact that the Earth's magnetic field is vital in protecting us from the Solar wind. However, one canny student wanted more info on exactly how this worked? After all, the magnets he was playing with seemed to only attract other objects, unless the object was a magnet and he tried to bring like poles together. He suggested maybe the solar wind was made up of tiny magnets, but then correctly suggested that if this was true, would they just turn around if they happened to be aligned the wrong way and then still be attracted to the Earth?

Of course, what is really going on is the Lorentz force due to the Solar wind (and other high energy particles) being ionised. I took a stab at explaining the Lorentz force in the simplest possible terms but I don't think I was very successful!

I've been thinking of how this could be shown with a simple demo, where by simple I'm ruling out any use of electron beams (cathode ray tubes etc). This is a primary school without access to such gear (and I don't have ready access through my work either). At a pinch an old CRT TV or computer monitor might be useful, but I'm a few years late. It's all flat screens at the school. We could play around with some simple motors and generators but I fear it's a little abstract trying to connect concepts from there to the solar wind and the magnetosphere. I've worked with high school students who've had a hard time getting their head around motors and generators so I think that might just be extra confusion for a 12 year old.

Does anyone have a simple explanation or demo of the Lorentz force as it applies in the shielding of the solar wind by the Earth's magnetic field?

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Have you showed your students the jumping wire? –  David H Aug 9 '13 at 3:00
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It is very difficult task to actually explain the Lorentz force to 12 year old. In fact, the concept of force alone is not that simple, let alone Lorentz guy.

I've worked in Science Museum for a while, and I came to conclusion that there is no need to explain everything. You must address feelings and imagination of that aged audience, not their brain. But you already know it.

Now, I don't know how to explain Lorentz force in a cosmological framework. However, there are few simple demonstrations of Lorentz force you can do. The best one is demonstrated in this video by (the greatest) Prof. Walter Lewin of MIT (around 12:00). Maybe you can use this demonstration and somehow draw a parallel between the current in the wire and solar wind.

You may also want to check out this site. Maybe you could apply some of the concepts you find there. There even an instruction for cosmological demonstration at the bottom, though the equipment is not that simple.

Hope this helps.

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+1 for Prof. Lewin! –  David H Aug 15 '13 at 13:42
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