What Causes the Aurora?

The aurora originates from the sun. The sun spits out charged particles that are carried to Earth via the solar wind. The aurora is caused when these protons and electrons from the solar wind are picked up by the earth's magnetic field (shown below). The particles are accelerated along a magnetic field line toward the poles and then are slammed into the Earth's upper atmosphere with enough energy to excite the nitrogen and oxygen atoms found there. After these atoms have been excited, they release the energy they have absorbed as photons, or visible light. It is this visible light that is emitted that makes up the aurora.