The Northern Lights Are Caused by the Solar Wind

The northern and southern lights begin on the Sun. NASA explains that the Sun continuously ejects a stream of charged particles called the solar wind. Earth has a magnetic field, which comes from the planet’s rapid rotation and its molten nickel-iron core, and the solar wind distorts that field into a teardrop shape in space. When charged particles from the solar wind become trapped in the magnetic field, they collide with air molecules above our planet’s magnetic poles. Those air molecules then begin to glow, and that glow is the aurora. The same magnetic field is what makes compass needles point north. It is not permanent. NASA notes that the field can flip direction, which the geologic record shows happens about every 300,000 years on average, though very irregularly.