One of the most beautiful things in nature, the Aurora Borealis or Northern Lights are the visible manifestation of particles hurling from the sun toward earth.
To understand the Aurora, we must first understand the magnetosphere.
The magnetosphere is a protective shield around our planet. It blocks most of the sun's dangerous charged particles. Without it, explosions on the sun would rip our atmosphere away, making earth habitation impossible.
The magnetosphere is a magnetic field. In the following image, a bar magnet is seen with its magnetic field. Notice the pattern of the field.
Because the earth's core is made of molten iron (a metal), it can be thought of as a magnet. Since it's a magnet, it must have a magnetic field. Our magnetic field is illustrated as the spider-like lines around the earth in this image.
A closer look shows that the magnetic field has openings to our atmosphere at the north and south pole. The north pole is illustrated here.
The sun's charged particles are able to enter the atmosphere through this gap at the north pole.This is symbolized in the following image with the small sphere right over the pole.
Charged particles are called "charged" because, well, they ARE charged. They have extra positive charges. Think of this as extra energy.
When the charged particles enter the atmosphere through the gap in the magnetosphere, those charged particles lose their extra energy. This loss is in the form of a plasma burst, as shown in the following image.
Repeat this millions of times for the millions of particles that stream toward the earth from the sun and you get the beautiful Aurora Borealis. At the south pole, this phenomenon is called the Aurora Australis.
The following image shows the Aurora Australis from the International Space Station.
From the ground, it looks even more spectacular! Here is a photo from Norway.