Astronomy 101: From the Sun and Moon to Wormholes and Warp Drive, Key Theories, Discoveries, and Facts about the Universe (Adams 101 Series)

by Carolyn Collins Petersen

The Sun constantly emits a stream of charged particles called the solar wind. As this wind rushes past Earth, it runs into our magnetosphere. That’s the region of space around Earth that is bound by our magnetic field. Most of the wind slides right on by, but some of the charged particles get caught up in the magnetic field lines. They spiral in toward the polar regions since those areas are where the magnetic field lines originate. The charged particles energize molecules of gas in our upper atmosphere, called the ionosphere. This causes them to glow. That glow is called the aurora. If it appears over the north pole, it’s called the aurora borealis; over the south pole it is called the aurora australis. Most of the time it glows white or green. However, if the solar storm is fairly energetic, more and different gases are energized and we can see reds and purples in spectacular auroral displays.