The Sun's rotation generates huge magnetic fields which shape active regions, sunspots and sculpt massive loops and prominences. The Sun is a magnetic, variable star...
Magnetism: The Key to Understanding the Sun: They have good background on magnetism.
NASA/GSFC Exploration of the Earth's Magnetosphere: The site to visit for a wealth of information on Earth's magnetosphere. Excellent historic information.
A Beginner's Guide to the Earth's Magnetosphere: Good easy-to-understand information.
Space Science Institute "Space Weather" Center: Terrific graphics and plenty of information on the Sun. Be sure to visit the Classroom Resources section.