Earth's Magnetic Field

If you've ever played with a compass, you have interacted with the Earth's magnetic field.  The Earth acts like a giant bar magnet.  The magnetic field of the Earth benefits us because it shields the surface of the Earth from dangerous levels of radiation from space.  We use it to navigate, as do some species of birds.  But, somewhat amazingly, scientists still aren't completely sure where the magnetic field of the Earth comes from.

The basic explanation for the magnetic field of the Earth is something called the "dynamo effect."  Molten iron in the core of the Earth carries electrical currents.  Due to the spinning of the Earth, these currents tend to build up, and their resulting magnetic fields build up as well.  Much the same way that electrical currents in a loop of wire can create an electromagnet, the Earth's magnetic field is born of loops of current inside the core.  However, the exact details of this are still fuzzy.  Making the whole question more complex is the evidence that the direction of the magnetic field of the Earth has reversed in the past.  How exactly does that happen?

A couple of years ago, some scientists used a supercomputer to model the flipping of the Earth's magnetic fields.  They visualized the output of their mathematical simulations using blue and orange lines to signify the field lines linked to the North and South poles of the Earth.  Their simulations model how the field might flip, showing the strange state of the magnetic field in the middle of the transition.  Below are images representing the Earth's field before and during a flip of polarity.

 

Check out the web page of the researchers who did this work.  You can view an animation of the magnetic field flip in action here. 

Finally, there is some recent evidence that perhaps this process of flipping happens really fast (well, fast on a geological timescale!)  Odds are if you lived through one of these magnetic field flips you would never notice, but it is intriguing anyway!  Here's a Science News article to find out more.