The aurora borealis and aurora australis – often called the northern lights and southern lights – are mysterious and unpredictable displays of light in the night sky. The most common occurrences of this phenomena take place at higher northern and southern latitudes, less frequent at mid-latitudes, and are almost never seen near the equator.
Auroras demonstrate the connection between the Sun and the Earth. The energy that comes off of the Sun is carried toward Earth by solar winds. As these particles approach Earth, they interact with Earth’s magnetic field. This field deflects a majority of these particles, but while doing so a huge cavity in the magnetosphere is created. When the amount of energy in the magnetosphere becomes too large, it loses its equilibrium. In order to become stable again, the excess energy is released into the acceleration of electrons. Essentially, the electrons transfer their energy to the oxygen and nitrogen atoms and molecules, ‘exciting’ them. As the gases return to their ground energy state, they emit photons, small bursts of energy in the form of visible light, creating the aurora.
Auroras which are usually green can occasionally show red, blue, violet, pink, and white in long, narrow arcs. The different colors of the aurora that are displayed depends on which gas is being excited by the electrons, and to what degree it becomes excited. High energy electrons cause oxygen to emit green light, while low energy electrons emit red light. Nitrogen normally gives off a blue light. The blending of all these colors can lead to the purples, pinks, and whites that we detect. Not much is known on how the shape of the aurora is determined, but scientists hypothesize that it may have something to do with where the electrons originate from, and what causes their gain in energy.
One thought on “The Aurora”
I have never seen Aurora lights in the northern hemisphere, but it is one of my long life dreams. It is one way to see the physics that you know in action. Like you explained, the interactions between electrons and Earth’s magnetic field, the fact that we can see that as evidence by these beautiful lights!