The interaction between light from the Sun, charged particles, and molecules in the atmosphere can create a variety of glowing phenomena. The best known are the Northern and Southern Lights. They truly put on a show, but they are not the only ones. A more subtle phenomenon is called airglow, and while it is possible to see it from the ground, it is from space that you can get the best view.
In an image snapped by astronaut Andreas Mogensen, a double airglow is visible in the atmosphere. The yellow glow is due to the particles of sodium in the atmosphere, while the red is caused by the oxygen and, to a lesser extent, hydroxyl (oxygen plus a hydrogen molecule) that is present even higher in the atmosphere.
This weak luminescence in the upper atmosphere is caused by the interaction between light and the molecules or atoms. Sunlight energizes molecules over the day, slitting them apart, or exciting electrons from their atoms. The energy is then lost in the following hours, due to collisions with other molecules. That emission of energy happens at a specific color, creating the characteristics of airglow that can be seen here.
Airglow forms from different molecules and at different altitudes.
Image Credit: © IFLScience
As long as there are molecules and atoms to excite, airglow can form. While most of it comes from a fairly narrow region, between 50 and 300 kilometers (31 to 180 miles), NASA reports that it can extend over twice as far. And while it is a pretty spectacle, it can also be very useful, providing insight in the motion and distribution of the extremely rarefied layers in the highest portions of the atmosphere.
Source Link: Astronaut Snaps Breathtaking View Of Earth’s Airglow From Space
