Aurora polaris (or aurora polaris) is a phenomenon in the form of brightness or luminescence that occurs in the night sky, usually in anal areas, although it may appear in other areas of the world for brief periods. In the southern hemisphere it is known as the southern aurora and in the northern hemisphere as aurora borealis (from Aurora, the Roman goddess of dawn, the Latin word Auster, which means south, and the Greek word Bóreas, which means north)
An aurora occurs when an ejection of charged solar particles collides with the Earth's magnetosphere. This “sphere” that surrounds us obeys the magnetic field generated by the Earth's core, formed by invisible lines that start from the two poles, like a magnet. There are also very energetic phenomena, such as glare or coronal mass ejections that increase the intensity of the solar wind. When said solar mass collides with our protective sphere, these solar radiations, also known as solar wind, travel along that sphere. In the hemisphere that is in the nocturnal stage of the Earth at the poles, where the other magnetic field lines are, this energy is stored until it can no longer be stored, and this stored energy is triggered in the form of electromagnetic radiation on the earth's ionosphere, creator, mainly, of these visual effects.
Earth's magnetosphere diverting charged solar particles (yellow lines) to the poles, where the auroras form
Image of a southern aurora around Antarctica photographed from a NASA satellite
Southern Aurora photographed from the North American base Amundsen-Scott, during the polar winter (the aurora lasted almost six months)
The Sun, located 150 million kilometers from Earth, continuously emits particles that constitute a flow of particles called solar wind. The surface of the Sun or photosphere is about 6000 ° C; however, when it rises in the Sun's atmosphere towards higher layers, the temperature increases instead of decreasing. The temperature of the solar corona, the outermost area that can be seen with the naked eye only during total solar eclipses, reaches temperatures of up to three million degrees. As the pressure on the surface of the Sun is greater than that of the surrounding space, charged particles that are in the Sun's atmosphere tend to escape and are accelerated and channeled by the Sun's magnetic field, reaching the orbit of other bodies large as Earth. There are also very energetic phenomena, such as glare or coronal mass ejections that increase the intensity of the solar wind.
The particles of the solar wind travel at speeds in an approximate range of 490 to 1000 km / s, so that they travel the distance between the Sun and the Earth in approximately two days. In the vicinity of the Earth, the solar wind is deflected by the Earth's magnetic field or magnetosphere. Particles flow into the magnetosphere in the same way as a river around a stone or a bridge pillar. The solar wind also pushes the magnetosphere and deforms it so that, instead of a uniform beam of magnetic field lines such as an imaginary magnet placed north-south in the interior of the Earth, what you have It is an elongated comet-shaped structure with a long tail in the opposite direction of the Sun. The charged particles have the property of being trapped and traveling along the magnetic field lines, so that they will follow the path that these . The particles trapped in the magnetosphere collide with the atoms and molecules of the Earth's atmosphere that are at their lowest energy level, at the so-called fundamental level. The energy supply provided to these causes high energy states also called excitation. In a short time, of the order of the millionths of a second, or even less, the atoms and molecules return to the fundamental level losing that energy in a wavelength in the spectrum visible to the human being, what vulgarly becomes the light in their different colors. The auroras remain above 95 km from the earth's surface because at that altitude the atmosphere is already dense enough that collisions with charged particles occur so frequently that atoms and molecules are practically at rest. On the other hand, the auroras cannot be higher than 500-1000 km because at that point the atmosphere is too dim — not too dense — so that the few collisions that occur have a significant effect on their light appearance.