Picking up where we left off...
The Earth: Most people learn about the layers of the Earth in middle school, but few remember much about the topic. The mantle is the most involved part of the Earth when discussing space weather. It is composed of many common metals, including large amounts of iron. Iron is important. These metals are in a semi-fluid state, where the heated portions near the core float up slowly, and the cooler metals nearer the crust sink to be re-heated. You can see this in a pot of water on your stove; were you to drop food colouring into a pot of water at a rolling boil, you would see the same pattern. Hot water moves up, it pushes surface water to the side, the cooler surface water sinks to start the cycle again (see here for a visual).
This circular motion is happening vertically under our feet all the time. Despite how slowly it happens (we suspect it takes tens or hundreds of millions of years for one convection cycle to complete), the motion of metal atoms against each other in the mantle causes an electromagnetic field around the planet.This field, called the magnetosphere, is one of the central players in space weather. Like the iron filings in this image (click here), the field curves in toward the magnetic poles of our planet. As we travel through space, it also compresses at our "front" and streams out behind us like an invisible comet's tail.
Why? Solar wind! Now next time (probably later tonight or tomorrow), we can finally get into solar activity and space weather!
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