Auroras

From the Sun comes an extremely thin electrified gas, known as the solar wind; it blows constantly out from the Sun at 250 miles per second. The Earth's magnetic field provides a shield against the solar wind. Shaped by the solar wind, the magnetic field becomes stretched and pushed into a teardrop-shaped bubble we call the magnetosphere. Some electrically-charged particles from the solar wind penetrate the magnetosphere, collide with the Earth's upper atmosphere, and emit colorful light which we observe as an aurora. The aurora form near-circular bands around both the northern pole (the aurora borealis) and southern pole (the aurora australis).

Recently, researchers were surprised to find that the two aurora are not mirror images of each other, as was once thought. This appears to be caused by fluctations in the tilt of the Earth's magnetic field, and conditions in the solar wind. Link.