Earth's Magnetic Field

If you're wondering what this has to do with aviation, you will be surprised at the relationship between this feature of our planet and cancer induced by radiation at altitude.

Here's an instance of why this type of information is important. From the Center for Aviation Research

Next Solar Max in 2011-2012. Better get out your No. 5Million sun block.

See Nasa's site on Solar Max (the equivalent of our earth's hurricane season). It happens every so many years. Significant event if you're flying near the poles.