Go to the north-west of Iceland towards the Hvammsfjördur, and our base of observation of the polar aurora ... the "Northern lights" as they say in Iceland, in Búðardal.
Particularly visible between 65 ° and 75 ° latitude, the aurora borealis is a luminous phenomenon characterized by colored sails, more visible without light pollution and caused by the interaction between charged particles of the solar wind and our upper atmosphere.
Thurranes cottages, an ideal base for observing the polar aurora, in the Búðardal - photo © Bernard Duyck 10.2016
The excitation of molecules of oxygen and nitrogen is at the origin of the main colors: oxygen emits mainly in green and red, while nitrogen emits blue, red and purple.
The phenomenon occurs especially between 100 and 1,000 km altitude, in the ionosphere The characteristic green is perceived much less "flashy" by the human eye than by the camera ... the always changing sails are of " Green gray ", with some shades of purple.
We had the chance to benefit from the conjunction of a correct solar activity and the time that came in the evening. The auroras were visible three nights in succession.
Aurora and history:
The auroras have worked the imagination of humans over the ages.
In ancient times, both in the West and in China, auroras were seen as serpents or dragons in the sky. They are associated with many myths and legends. All languages evoke these "the northern lights" with the exception of Finns who use the Finnish term of revontulet and which can be translated as "red fox tail" or "fox fires": some Sami people say that the polar fox , by rapidly traversing the vast snowy expanses, ejects dust with its tail in the sky, thus creating the aurora borealis along their passage.
In Greenland, the Inuit nicknamed the aurora aqsarniit, believing that the souls of the dead play ball with walrus skulls. A tribe of the Nunuvat thinks the reverse that it is the walruses who play ball with human skulls. Their red color associated with blood is responsible for the fact that the Inuit of East Greenland believe that the polar aurorae are the soul of stillborn children.
Other northern mythologies evoke the Bifröst, the dance of the spirits of certain animals, particularly salmon, reindeer, seals and belugas; the whales of the Arctic Ocean; the reflection of the Sun or the Moon on the armor of the Valkyries when they cross the Sky; torches lit by the spirits of the dead to welcome newcomers to paradise.
In Europe in the Middle Ages, polar auroras that take on red hues are associated with blood and war. They foreshadow a catastrophe or are seen as the breath of the celestial warriors who tell their fights in the sky. (Wikipedia)
In 593 BC, the Greek Anaximene would have seen "clouds of inflamed gas". It seems that this would have been a polar aurora.
Sunspots had been noticed by Chinese astronomers in the 15th century.
In the 17th century, Galileo was the first to use the term "aurora borealis" to name this phenomenon, but it seems that he had not yet found the explanation. He had noticed the sunspots (dark spots, colder than the rest of the solar surface, whose magnetic field is very high).
During the 19th century, some 27 scientific theories attempted to explain, without success, the aurora phenomenon. Some astronomers had an association between sunspots and auroras that were abnormally intense.
During the first half of the twentieth century, a Norwegian, Olaf Birkeland associated auroras with electric currents created in the atmosphere by solar particles.
Over the past 30 years, satellite measurements have made it possible to understand the causal relationship between sunspots and auroras. The more numerous spots, the more auroras become visible in populous regions.