This aurora display includes green light emissions from oxygen atoms as well as a purple glow produced by nitrogen molecules.
Click on image for full size
Image courtesy of Jan Curtis.
Colors of the Aurora
The aurora (Northern Lights and Southern Lights) are caused by collisions between energetic particles in Earth's magnetosphere and atoms or molecules in the upper atmosphere. Particles, mostly electrons and protons, are accelerated to high speeds and energies as they spiral along Earth's magnetic field lines. The particles bounce back and forth between Earth's magnetic poles, where magnetic field lines dip into the planet's upper atmosphere. Some of the energetic particles collide with atoms and molecules of oxygen and nitrogen in the upper atmosphere near the poles.
These collisions add energy to the atoms, which in turn shed the excess energy by emitting light. The brilliant displays of auroral lights have characteristic colors which depend on the type of atoms or molecules which are giving off the light. Oxygen atoms emit green light that is seen in many auroral displays. Oxygen atoms above 150 km (93 miles) in altitude can also give off red light. Energized nitrogen molecules emit red, blue, and violet light.
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
One main type of radiation, particle radiation, is the result of subatomic particles hurtling at tremendous speeds. Protons, cosmic rays, and alpha and beta particles are some of the most common types...more
The Earth has a magnetic field with north and south poles. The magnetic field of the Earth is enclosed in a region surrounding the Earth called the magnetosphere. As the Earth rotates, its hot core generates...more
The thermosphere is a layer of Earth's atmosphere. The thermosphere is directly above the mesosphere and below the exosphere. It extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to...more
Charged particles cannot easily move across magnetic field lines but are forced to spiral around them. Electrons encirle the field line in one direction, ions in the other direction....more
Not only do particles spiral around magnetic field lines but they also move along the field lines toward the Earth. The crowded magnetic field lines near the poles cause particles to "reflect" and move...more
Earth has a magnetic field. If you imagine a gigantic bar magnet inside of Earth, you'll have a pretty good idea what Earth's magnetic field is shaped like. Of course, Earth DOESN'T have a giant bar magnet...more
Oxygen is a chemical element with an atomic number of 8 (it has eight protons in its nucleus). Oxygen forms a chemical compound (O2) of two atoms which is a colorless gas at normal temperatures and pressures....more