The night of San Juan is the longest in history, celebrated with a traditional combination of legends, bonfires and fire. Over the years, a growing fleet of tourists has started heading to the North Pole, near the Arctic districts and to the highest point of the Scandinavian countries. Tourists came in search of another fantastic phenomenon of nature: the midnight sun. The Aurora Borealis is a natural phenomenon that occurs throughout the year and can be seen very often in the clear nights of those places located in latitudes close to the poles of the Earth.
The where, why, when and how’ of the Auroras have not yet been answered in this space. Let’s shift the focus to the untouched questions of the happenings of Aurora Borealis facts and grasp more.
1 What Are The Northern Or Southern Auroras? Why & How Do They Happen?
This phenomenon occurs equally in the south, and is known as the Southern Aurora, but this hemisphere is less populated and has been seen less. For centuries humans have associated the Aurora Borealis or the northern lights to all kinds of legends and mythological explanations.
It is not easy to resist interpreting as a sign of heaven or divine designs. The dances of lights draw vibrant red skies, roses, and coloured curtains that dance across the sky, serving as a screen to the stars.
Legends will continue to exist – luckily no one can eliminate that even in a world increasingly dominated by technological advances. But its base will cease to be real as we know more about the mysterious physical process that unleashes this incredible natural phenomenon.
2 The Mysteries Of The Aurora Borealis
The collision of the charge of the particles with the atmosphere results in aurora. The explosion of energy is responsible for the violent increase of luminosity and movement in the northern lights.
In 2007, a team from NASA launched THEMIS mission, composed of five satellites located at strategic points of the magnetic field of Earth. The mission aimed to give an understanding of what happens and how an Aurora is formed. In July 2008, they announced with great fanfare the results. The results have solved a mystery that the physical scientific community has been debating for more than 30 years.
3 Principle Behind Aurora Borealis
The principle is the activity of the sun that generates the solar wind to the Earth and a great amount of energy in the form of matter comes loaded with electrons. These immense energy waves are enough to cause real storms in space assimilated by Earth’s magnetic field, which acts as a safety belt.
The magnetosphere is in charge of maintaining an area of relative tranquillity in the meteorological conditions of the planet. But there comes a point where the accumulated energy has to be released. This is when a magnetic sub-torment is triggered that throws the matter charged at full speed to the poles of the Earth and that when it reaches the atmosphere produces the dance of lights called Aurora.
Specifically, the Aurora Polar is the phenomenon produced by the solar mass ejection colliding with the North and South poles of the Earth’s magnetosphere. The charged particles of energy (protons and electrons) from the Sun are guided by the Earth’s magnetic field towards the poles.
When particles collide with atoms and molecules of oxygen and nitrogen in the upper layers of the atmosphere, the particles release their energy so that it is returned by the atoms in the form of visible lights in the skies of the North and South Pole.
4 What Causes Different Colours & Intensity?
It is known that the sub-torments are located at the origin of the auroras, but perhaps not so much that the magnetosphere supports from one to three sub-torments per day. They happen very frequently, although that does not always translate into a particular firework of stars. To see the auroras one has to take into account certain meteorological conditions.
They are visible only at night i.e. when the sky is clear and cloudless and the further north, near the pole. The inhabitants of Iceland can see them almost every night. However there are imperceptible auroras and others as strong as that which could be seen even in the Canary Islands in 2003.
“The difference in intensity is due to the difference of charged particles in space. Most auroras are caused by electrons and you have to think that in an aurora of medium intensity, a square millimeter is hit by a hundred million electrons per second, the quantities are gigantic “, explains Ingrid Sandahl, professor of the Swedish Institute of Space Physics, in Kiruna (Sweden).
5 What About The Different Colours?
Sandhal explains: “The atmosphere is composed of a large number of oxygen atoms; so when electrons collide with oxygen particles we see that each atom has a particular colour.” Atoms and colours tell us the composition of the atmosphere when struck. Green is the most common colour, and is caused by oxygen, just like red.
6 What Causes The Auroras?
Until recently no one knew what the origin of the sub-torments was, that the process was unleashed or what factors were pressing the red button to blow up the safety belt.
Scientists shuffled two hypotheses. One of them says the sub-torments occur near the Earth, or more precisely, one-sixth of the distance between the Earth and the Moon, about 60,000 kilometres. The energy comes from a powerful electric current that flows through the magnetosphere at this distance, composed of plasma or a mass of electrons and charged ions. These ions are released suddenly due to an explosion. The plasma is directed towards the Earth and the spatial currents are interrupted which causes the origin of the sub-torment.
The second hypothesis places the phenomenon at a third of the distance from the Moon and Earth, and states that the discharge of energy occurs in the tail of the magnetosphere. Around the tail the magnetic fields point to opposite directions, one towards the outside in the North Pole and another towards the interior in the South Pole. When the magnetic field lines converge, a reconnection takes place that cuts the tail in two, creating a sub-torment.
The team Vassilis Angelopoulos by Themis mission at NASA, confirmed the latter case from the observations collected by satellites in an article published by Science in July last year.
“Our data clearly show for the first time that magnetic reconnection is the trigger. Reconnection is an acceleration of waves and plasma along the magnetic lines that light up the aurora below the Earth before the near areas of the aurora in space have had the opportunity to respond. We can provide the data and demonstrate that this is what happens, “says Angelopoulos.
Some supporters of the contrary theory still do not seem convinced to have lost the battle and point out that the NASA satellites were not in the right position. The Angelopoulos team repeated the experiments with similar results, but continues to look for more evidence to close the discussion.
7 The Weather Conditions Of The Space
The light effect is dominated by the emission of oxygen atoms in high atmospheric layers (around 200 kilometres of altitude), which produces the green tonality. When the storm is strong, lower layers of the atmosphere are hit by the solar wind (around 100 kilometres of altitude), producing the dark red hue by the emission of nitrogen atoms and oxygen. Oxygen atoms emit very varied colour tones, but the predominant ones are red and green.
The phenomenon can also be observed with ultraviolet, violet or blue illumination, originating from nitrogen atoms.
8 Impacts Of Aurora Generation
The results of the mission are of great importance in the ever-expanding field of Space Time. As Jim Wild, a professor at the University of Lancaster in the UK, explains-
“Today in our life forms we have satellites to navigate, we have GPS, our distribution networks, electricity network flows, we use radio communication And we have a lot of technology and people in the orbits of space … Some of these systems could be vulnerable to space time, and there have been cases of satellites damaged by sub-torments or in some cases electrical networks that have been affected.”
The knowledge of how the auroras are generated will allow greater control of this space time. However, the challenges to control the meteorology in the infinite space of galaxies and the Solar Systems do not stop being few.
“The problem of making measurements in space is that it is immense and it is impossible to have a complete vision. The challenge is to combine the information provided by satellites with theoretical computer models that help us to plug holes. It is not possible to know what happens in space time only with the data collected in a small part of it,” says Wild, for him would be like “trying to understand a storm on Earth with the measurements of four thermometers.”
Researchers like Ingrid Sandahl focus on those auroras that are not produced by sub-torments, structures of small scales that happen to be less than 100 meters and are almost imperceptible. They come up with duration of a second sometimes to understand the phenomenon.
“Knowing more about these small structures will help us know much more about the details of the particular physical processes that occur in the ionosphere. Auroras are a great channel for understanding our own environment. There is a lot of energy that is produced in the aurora and we still do not know how this energy affects the lower levels of the atmosphere. It is a fundamental instrument of plasma physics, of the foundations of physics”
For Sandahl, auroras are a fundamental laboratory of natural physics. There is no more beautiful definition in essence to summarize one of the most wonderful phenomena of our firmament.
9 Artificial Aurora
Auroras can also be formed by nuclear explosions in upper atmosphere (about 400 km). This phenomenon was demonstrated by artificial aurora created by the US nuclear test Starfish Prime in July 9, 1962. At that time, the sky of the Pacific Ocean was illuminated by the aurora for more than seven minutes.
Nicholas Christofilos, who had worked on other projects on nuclear explosions, had predicted such effect. According to veteran American Cecil R. Coale, some hotels in Hawaii offered rainbow bomb parties on their roofs to accompany Starfish Prime, contradicting official reports that the artificial aurora was unexpected. The phenomenon was also recorded on film in the Samoa Islands, about 3,200 kilometres away from Johnston Island, the site of the blast.
10 Aurora On Other Planets
Jupiter as Saturn have much stronger magnetic fields that Terrans (Uranus, Neptune and Mercury), and both have large radiation belts. The effect of the polar aurora has been observed in both, more clearly with the telescope Hubble.
Such auroras appear to be from the solar wind. On the other hand, the moons of Jupiter (especially Io) are also powerful sources of auroras. They are formed from electric currents by the magnetic field, generated by the dynamo mechanism relative to the movement between the rotation of the planet and the translation of its moon. Particularly, Io has active volcanoes and ionosphere, and its currents generate radio emissions, are in study since 1955.
11 History Of Research On Aurora
The Auroras have been scientifically studied since the 17th century. In 1621, the astronomer Frenchman Pierre Gassendi described the phenomenon observed in southern France. In the same year, Italian astronomer Galileo Galilei began investigating the phenomenon as part of a study of the celestial star movement.
As his radius of his study was limited to Europe, the fact of checking the phenomenon in the north of the continent led him to call it “aurora boreal”.
In the 18th century, the English navigator James Cook witnessed the same phenomenon of Galileo in the Indian Ocean, naming it the southern aurora. From then on it was clear that the effect was not unique to the terrestrial northern hemisphere, creating the denomination polar aurora. At the same time, the British astronomer Edmond Halley suspected that the earth’s magnetic field was related to the formation of boreal auroras. In 1741, Olof Hiorter and Anders Celsius were the first to report evidence of magnetic control when there were observations of auroras.
In 1768, Henry Cavendish, calculated the altitude at which the phenomenon occurs. It was only in 1896 that an aurora was reproduced in the laboratory by Kristian Birkeland. The experiments in a vacuum chamber with electron beams and magnetic beams showed that such electrons were being guided to the polar region. He proposed in around 1900 that the auroral electrons originate from solar rays. This model lacks evidence in space, and is obsolete in current research. Birkeland also inferred in 1908 that currents of magnetism flowed east-westward.
More evidence in connection with the magnetic field is the statistical records of the polar auroras. Elias Loomis (1860) and later more in detail Hermann Fritz (1881) established that the aurora appears mainly in a ring-shaped region with a radius of approximately 2,500 kilometers around the Earth’s magnetic pole. Loomis was also responsible for discovering the relationship of aurora to solar activity, noting that between 20 and 40 hours later of a solar eruption, the aurora borealis appeared in Canada.
12 The Polar Aurora In The Cultures Of People
In the 19th century was the belief that the polar auroras were reflections of city lights inside the planet, and that the poles would be inputs and outputs. These worlds would be parallel. For many years a number of people have truly believed in this possibility.
Throughout history people have been writing and talking about sounds associated with the images of the dawn. The Danish explorer Knud Rasmussen mentioned this effect in 1932 while describing folk traditions of the Eskimos of Groeeland. The same sounds in the same context are mentioned by Canadian anthropologist Ernest Hawkes in 1916.
Tacitus, a historian of ancient Rome, wrote in his “Germania” that the inhabitants of present – day Germany cheered hear them the same way. Many people today continue to report such sounds, although their recordings have never been published. There are scientific problems with the idea of auroral sounds being heard.
13 Polar Aurora In Classic Literature
In the classic book by Thomas Bullfinch, 1855, “Mythologies”, there is a quote from Norse mythology related to the phenomenon: “The Valkyries are virgins of war, mounted on horses and armed with helmets and spears. When they ride forth on their message, their armour shed a strange light that flickers, which lights up over the northern skies, making what men call ‘aurora borealis’ or ‘northern lights’.
Despite a striking description, there are no citations in Scandinavian literature to support such an assertion. Although auroral activity is common in the region in which Scandinavia is situated, it is possible that the magnetic north pole was considerably further away from this region in the centuries prior to the documentation of mythology, thus explaining the lack of references.
The first citation in Norse mythology is found in chronic “Konungs skuggsjá ” (1250). Its author had heard about the phenomenon of compatriots returning from Greenland, and provides three explanations: that the ocean was surrounded by vast fires that sunlight could reach the ” night side ” of the world, or that the glaciers could store energy Eventually become fluorescent.
14 Polar Aurora & The Associated Etymology
An old Scandinavian name for northern lights translates as “herring flash”. It was believed that the lights were reflections thrown by large shoals of herring into the sky. Another Scandinavian source refers to fires that surround the north and south ends of the world. This shows that the Norse even ventured into Antarctica, though only one quotation is insufficient to form a solid conclusion.
The Finnish name for the dawn is “revontulet” which means “fox fires”. According to legend, the fire made foxes lived in Lapland, and “revontulet” were the sparks that they threw into the atmosphere with their tails. In Estonian is called “virmalised”, “spirits of the higher realms.” In some legends they have negative character, while others positive.
The Sami people believed should be careful and quiet to observe the northern stars (called “guovssahasat” in their language), but they could come down and kill the observer. Algonquins, however, believed that the lights were their ancestors dancing around a ceremonial fire. In Inuit folklore, the aurora borealis was composed of dead spirits playing soccer with a walrus skull across the sky. They also used the dawn to call their children home before the darkness, claiming that if the person made sounds in their presence she would lower and burn her.
15 Aurora & Its Emission
The polar aurora is an optical phenomenon composed of a glow observed in the night skies in the polar region, extreme north and extreme south. It occurs due to the impact of solar wind particles and the space dust found in the Milky Way with the high atmosphere of the Earth, channelled by the earth’s magnetic field.
In northern latitudes it is known as “Northern Lights” (name baptized by Galileo Galilei in 1619, in reference to the Roman goddess of dawn, Aurora, and his son, Boreas, representing the north winds). It normally occurs from September to October and from March to April. In southern latitudes it is known as “Aurora australis” (name baptized by James Cook, a direct reference to it being south).
The phenomenon is not only unique to the Earth, but is also observable on other planets in the Solar System, such as Jupiter, Saturn, Mars and Venus. In the same way, the phenomenon is not unique to nature, and is also artificially reproducible through nuclear explosions or in laboratories.
The terrestrial polar aurora is caused by electrons of energy from 1 to 15 keV, in addition to protons and alpha particles. The light is produced when they collide with atoms of the planet’s atmosphere, predominantly oxygen and nitrogen, and typically at altitudes between 80 and 150 kilometers. Each collision emits a part of the energy of the particle to the atom that is reached, a process of ionization, dissociation and excitation of particles. When ionization occurs, electrons are discharged from the atom, which carry energy and create a domino effect of ionization on other atoms.
The excitation results in emission, leading the atom to unstable states, which emit light at specific frequencies as they stabilize. While oxygen stabilization takes up to a second to happen, nitrogen stabilizes and emits light instantly. Such a process, which is essential for the formation of the terrestrial ionosphere, is comparable to that of a television screen. In a television screen, electrons reach a phosphorus surface, changing the energy level of the molecules and resulting in the emission of light.