polar aurora

A luminous phenomenon that takes place in the upper atmosphere, at altitudes above 100 km, and that is habitually observed in the polar regions. It is the result of the interaction of the solar wind with the Earth's atmosphere. Part of that flow of highly energetic electrical particles, radiating from the sun in all directions, is intercepted by the Earth's powerful magnetic field, which acts as a protective shield and diverts it toward the two magnetic poles. The bombardment of particles onto the gaseous molecules present in the upper atmosphere results in the emission of light at different wavelengths (different colors) and, consequently, the formation of polar auroras. Their hues depend on the type of molecules bombarded. Oxygen molecules form green-colored auroras; nitrogen produces glows in red, pink, and purple tones, while the less frequent blue color comes from hydrogen molecules, located very high up in the atmosphere. Depending on the Earth's hemisphere where they form, we have aurora borealis (northern hemisphere) and aurora australis (southern hemisphere). Large geomagnetic storms, caused in the Earth's magnetosphere by the arrival of a solar wind more intense than normal, result in larger polar auroras, which can be observed at lower latitudes than usual. Aurora borealis are also known as the northern lights and there are many legends surrounding them. In some Nordic cultures it was thought they were the souls of the dead, who dwelt above the atmosphere and danced with lit torches to guide the steps of new spirits.