What causes the northern lights?
The northern lights are caused by charged particles from the Sun colliding with gases in Earth's upper atmosphere. Earth's magnetic field guides them toward the poles, where they make the sky glow.
The Sun constantly releases a stream of charged particles called the solar wind. When these particles reach Earth, most are deflected by the planet's magnetic field, but some are funneled toward the polar regions. There they crash into oxygen and nitrogen atoms about 100 to 300 kilometers above the ground, giving them energy that is released as light.
The colors depend on which gas is hit and at what height. Oxygen produces the most common green glow and, higher up, rare red light. Nitrogen gives blue and purple shades. The lights can appear as curtains, arcs, spirals or flickering rays that move across the sky.
Where and when to see them
The northern lights, or aurora borealis, are best seen in places like Norway, Iceland, Finland, Canada and Alaska on dark, clear nights between autumn and spring. In the Southern Hemisphere, the same effect is called the aurora australis. Strong solar storms can push auroras far from the poles.
Did You Know?
During a powerful solar storm in May 2024, auroras were seen as far south as Mexico, Florida and northern India.