What causes the northern lights?


The aurora borealis are magnificent jets of color illuminating the sky in certain regions of the world, mainly in high latitude countries. But what are they due to?

Mostly visible between September and March in Scandinavia, Iceland, Alaska, or in the Canadian North, the aurorae are caused by electrically charged particles coming from the Sun. They enter the Earth's atmosphere at very high speed through the solar winds. The majority of these particles (about 98%) are deflected by the Earth's magnetic field, but the rest land at the North or South poles (for the aurora australis). When these particles collide with the atoms of our atmosphere, they go into a state of excitation. It is then when the atoms return to their basic state that they emit photons in specific wavelengths: red or green for oxygen atoms, and violet for nitrogen atoms.

This phenomenon has existed for thousands of years and has given birth to numerous legends. For example, the Vikings believed that the northern lights were the reflection of light on the armors of the Valkyries, who accompanied fallen warriors to join the god Odin. In Finland, legend has it that the aurora is created by an Arctic fox galloping and throwing snow into the sky.

By their nature, aurorae can occur on any celestial body in the solar system, as long as it has an atmosphere. The planets Jupiter and Saturn have stronger magnetic fields than the Earth, and auroras have already been observed on them.