How do the northern lights form?

The Sun constantly streams out charged particles known as the solar wind. When these particles reach Earth, our planet magnetic field funnels some of them toward the polar regions. There, high in the atmosphere, they collide with atoms and molecules of gas such as oxygen and nitrogen, transferring energy that makes the gases glow. Oxygen tends to produce green and red light, while nitrogen can give blue and purple hues. The result is the shimmering curtains of colour called the aurora, seen near both poles. Stronger solar activity produces brighter and more widespread displays.