Earth Observatory– Yesterday (January 23), the Sun spit off a powerful solar flare and released a coronal mass ejection. You can watch a video of this here. Coronal mass ejections include subatomic particles, like electrons and protons, and those particles were accelerated toward the Earth by the solar flare.
Today, those particles are going to be interacting with the high altitude atmosphere. When the particles hit atoms in the atmosphere, the atoms’ electrons can become energized. The electrons then release light when they lose energy- this is why I’m excited. This is what causes auroras, or the northern and southern lights!! Depending on the weather, there’s a slight possibility that we might be able to see some in Wisconsin tonight!
For a better and more thorough explanation of this all, read Bad Astronomy.
Update: BA added a post on how the aurorae are looking so far, and what our chances of seeing one tonight will be.