What causes the Northern Lights?
The Sun constantly blows out a stream of charged particles, the solar wind. Earth’s magnetic field steers some of them down toward the poles, where they crash into the air about 100 to 300 kilometers up. The collisions make oxygen and nitrogen glow, like the gas in a neon sign.
The Sun blows out particles
The Sun constantly throws off charged particles, mostly electrons and protons, which stream through space at hundreds of kilometers per second. After big eruptions on the Sun the stream gets much stronger.
Share this stepEarth’s magnetic field steers them
Earth’s magnetic field acts like a shield and deflects most of the particles. But near the poles the field lines curve down toward the ground, and some particles follow them into the atmosphere.
Share this stepThe air lights up
When the particles hit the air high above the ground, they give their energy to oxygen and nitrogen, which release it as light. Oxygen glows green, or red higher up, while nitrogen adds purple and blue edges.
Share this stepSolar wind meets the air, and the sky glows.
Solar windmagnetic fieldNorthern Lights
The same thing happens at the South Pole, where it’s called the Southern Lights. The lights are usually seen in a ring around the poles, but during strong solar storms they can appear much farther south.
Common follow-up questions
Where can you see the Northern Lights?
Best in a ring around the Arctic, such as northern Norway, Sweden, Finland, Iceland, Canada and Alaska. During strong solar storms they can be seen much farther south.
When is the best time to see them?
On dark, clear nights from about September to March, usually between 9 pm and 2 am, away from city lights. Aurora forecasts show how active it’s expected to be.
Why do photos look brighter than real life?
Cameras collect light for several seconds and pick up colors the eye struggles to see in the dark. Weak auroras often look gray or pale green to the naked eye.
Do the Northern Lights make sound?
Most of the time they’re silent, but some people report faint crackling during strong displays, and researchers have recorded sounds that may be linked to them.
