The wonders of high latitudes
Do you know about the optical phenomena that happen at high latitudes? Today I will begin to tell you about some of them...
The most popular phenomenon are the polar lights, named after the Roman goddess of dawn, Aurora. When they occur in the northern hemisphere they are known as "boreal" (for Boreas, the Greek god of the north winds) and in the south as "australis" (from the Latin meaning, "southern land").
These light curtains in the sky occur as a result of the interaction of highly charged particles ( =plasma!) that arrive with the solar wind and collide with the Earth's magnetic field. The magnetic field lines direct these particles towards the poles and when they enter into contact with the atmosphere (usually the ionosphere), they collide violently with gas atoms. This transfers energy to the gas atoms, which causes them to release light and electrons, in a process of ionization.
The color of the aurora depends on what gas is being excited by the electrons and how much energy is being exchanged. Oxygen emits a greenish-yellow light (the most familiar color of the aurora) or a red light, nitrogen generally emits a blue-purple light.
Auroras are not unique to Earth, the Hubble Space Telescope has also captured them on polar regions of other planets such as Venus, Mars, Saturn and Jupiter because they have magnetic fields and large radiation belts. Astronauts living in orbit on the International Space Station, can also see them on the Earth from above.
I had the chance to see this one in the photo while working the night shift on the R/V Atlantis, just off the coast of Greenland. It is difficult to capture it well because of the movement of the boat and the light itself, but it was certainly an experience that I will never forget and that always captures the imagination of people I show it to!