The northern lights are a mystical, unpredictable and beautiful phenomenon that suddenly appears and just as suddenly disappears. In this article, in addition to breathtaking photographs, you will learn about what kind of phenomenon this is, get acquainted with a number of interesting facts that you probably didn’t even know about. We will even delve into the ancient history and folklore of various peoples to learn more about the origin of the northern lights. If the theory is too complicated for you, leave your questions in the comments, and be sure to get a detailed answer. I look forward to your feedback, additions and comments.
In past issues of LifeGlobe, we have written about such wonderful natural phenomena as rainbows, as well as unusual clouds. Today I will tell you about the Northern Lights. This is the glow of the upper layers of the planet’s atmosphere, which have a magnetosphere, due to their interaction with charged particles of the solar wind.
The Northern Lights are an amazingly beautiful, breathtaking sight. It can last from several hours to several days.
The answer to the question, what is it, was the first to find Mikhail Lomonosov. After conducting countless experiments, he suggested the electrical nature of this phenomenon. Scientists who continued to study this phenomenon, on the basis of experiments, confirmed the correctness of his hypothesis. They filled hollow tubes with nitrogen, neon, hydrogen, argon and other rarefied gases, passing an electric current through them. Each gas glowed (luminesced) differently. Then it was found that the glow of rarefied gases occurs in the upper part of the atmosphere — the ionosphere (at an altitude of 80 to 1,000 km). A close connection with the activity of the Sun was also revealed. When explosions occur on it, charged particles (corpuscles) rush into the Earth’s ionosphere. Colliding with particles of rarefied gases located in the ionosphere, they make them glow: the more active the Sun, the more the northern lights cover a larger area of the sky. This phenomenon is especially strong during the maximum period of the 11-year cycle of solar activity.
So, the northern lights arise as a result of the bombardment of the upper atmosphere by charged particles moving towards the Earth along the geomagnetic field lines from a region of near-Earth outer space called the plasma layer. The projection of the plasma sheet along the geomagnetic field lines onto the Earth’s atmosphere has the form of rings surrounding the north and south magnetic poles (auroral ovals). Space physics is engaged in revealing the reasons leading to precipitation of charged particles from the plasma layer. It has been experimentally established that the orientation of the interplanetary magnetic field and the pressure of the solar wind plasma play a key role in stimulating precipitation. In a very limited area of the upper atmosphere, auroras can be caused by low-energy charged particles of the solar wind entering the polar ionosphere through the north and south polar cusps. In the northern hemisphere, cusp aurora can be observed over Svalbard around noon. When energetic particles of the plasma layer collide with the upper atmosphere, the atoms and molecules of the gases included in its composition are excited. The radiation of excited atoms is in the visible range and is observed as aurora. The spectra of auroras depend on the composition of the atmospheres of the planets: for example, if for the Earth the emission lines of excited oxygen and nitrogen in the visible range are the brightest, then for Jupiter, the emission lines of hydrogen in the ultraviolet. Since ionization by charged particles occurs most efficiently at the end of the particle path and the density of the atmosphere decreases with height in accordance with the barometric formula, the height of the appearance of auroras depends quite strongly on the parameters of the planet’s atmosphere, for example, for the Earth with its rather complex composition of the atmosphere, a red glow of oxygen is observed at altitudes of 200–400 km, and the combined glow of nitrogen and oxygen at an altitude of ~110 km. In addition, these factors also determine the shape of the auroras — a diffuse upper and rather sharp lower boundaries.
The northern lights are observed mainly at high latitudes of both hemispheres in oval zones-belts surrounding the Earth’s magnetic poles — auroral ovals. The diameter of the auroral ovals is ~3000 km during the quiet Sun, on the day side the zone boundary is 10–16° from the magnetic pole, and on the night side it is 20–23°. Since the Earth’s magnetic poles are ~12° apart from the geographic poles, auroras are observed at latitudes of 67–70°; however, during solar activity, the auroral oval expands and auroras can be observed at lower latitudes, 20–25° south or north of their boundaries. normal manifestation. The northern lights in spring and autumn appear much more often than in winter and summer. The peak frequency falls on the periods closest to the spring and autumn equinoxes. During the aurora, a huge amount of energy is released in a short time (during one of the disturbances recorded in 2007 — 1?2 joules, about the same as during an earthquake of magnitude 5.5. When observed from the Earth’s surface, the aurora appears in the form a general rapidly changing glow of the sky or moving beams, bands, crowns, “curtains.” The duration of auroras ranges from tens of minutes to several days.
The magnetic fields of the giant planets of the solar system are much stronger than the Earth’s magnetic field, which causes a larger scale of the auroras of these planets compared to the auroras of the Earth. A feature of observations from the Earth (and in general from the inner regions of the solar system) of the giant planets is that they face the observer with the side illuminated by the Sun and in the visible range their auroras are lost in the reflected sunlight. However, due to the high content of hydrogen in their atmospheres, the radiation of ionized hydrogen in the ultraviolet range and the low albedo of the giant planets in the ultraviolet, with the help of extra-atmospheric telescopes (the Hubble space telescope), fairly clear images of the auroras of these planets were obtained. A feature of Jupiter is the influence of its satellites on the auroras: in the areas of “projections” of beams of magnetic field lines on the auroral oval of Jupiter, bright areas of the aurora are observed, excited by currents caused by the motion of satellites in its magnetosphere and the ejection of ionized material by satellites — the latter is especially pronounced in the case of Io with its volcanism. On the image of the aurora of Jupiter, made by the Hubble space telescope, the following projections are noticeable: Io (spot with a “tail” along the left limb), Ganymede (in the center) and Europa (slightly below and to the right of the Ganymede footprint).
However, scientific definitions seem too dry and soulless when colored rays and stripes run across the sky, or a multi-colored pulsating curtain flashes across the whole space from east to west.
In ancient times, people did not understand nature, so many myths and beliefs are associated with the Northern Lights.
In ancient Norse mythology, the Bifrost Bridge is often mentioned — a burning, trembling arch that crosses the sky, along which the gods could descend from heaven to earth. It is possible that the aurora borealis was the prototype for this bridge. In some legends, the rays of the aurora borealis are perceived as fires carried by Valkyries (daughters of a glorious warrior or king who soar on a winged horse over the battlefield and select the most brave warriors to take them after their death to the heavenly chamber of Valhalla). Warrior maidens are depicted wearing helmets, with shields and spears; from the brilliance of their armor, according to legend, the northern lights appear in the sky.
In addition to the Bifrost bridge, Finnish mythology refers to the river — Ruja — which burns with fire, and marks the border between the realms of the living and the dead.
In Norwegian folklore, the northern lights were described as a harbinger of bad weather: it was assumed that the bright flashes were followed by snow and wind. Other Norwegian folk legends say that the northern lights are a heavenly dance of the souls of dead maidens.
The Eskimos in the Hudson Bay area of North America, as well as elsewhere, know a great deal about the phenomenon of the northern lights. There is a myth among the Eskimos that the aurora can be caused by whistling, while clapping your hands will make it go out. Other Eskimo myths say that the aurora is caused by spirits playing sky football with a walrus skull.
Some Inuit groups regard the northern lights as an indicator of good weather to be brought by the spirits. The Eskimos at Poit Barrow in Alaska saw the northern lights as malevolent, and carried weapons with them for protection if they needed to go outside during the northern lights. Also, some Eskimos say: “He who looks at the northern lights for a long time will soon go crazy!”
Some tribes of North American Indians believe that the northern lights are the light of lanterns carried by spirits searching for the souls of dead hunters. Like the Eskimos of Poit Barrow, the Fox Indians of Wisconsin feared the aurora, seeing it as the ghosts of their dead enemies. Other tribes experienced the northern lights as the light of the lights used by the all-powerful northern shamans.
The Northern Lights also entered the folklore of the Australian Aborigines, who saw them as the dance of the gods across the sky. The Northern Lights were very possibly the source of Chinese dragon legends. The serpentine forms of auroral active zones are often depicted as celestial serpents in ancient chronicles. European dragon legends, too, may have their origin in aurora activity. How ironic that nowadays many historians believe that the legendary battle of the patron saint of the English (St. George) was most likely with this frequent Scottish phenomenon, the aurora, and not with the dragon!
In the recent past, misconceptions about the cause of the aurora were still common among the general public. For example, many people in the American Midwest believed that the aurora was the reflection of sunlight off the polar ice, overlooking the endless darkness of the winter months in the Arctic! Another romantic explanation was that the light of the aurora is the result of iceberg collisions in the polar seas.
The most impressive Northern Lights appear with a cycle of 11 years and 22 years, depending on solar activity. Satellite imagery confirmed the old theory that the auroras in the northern and southern hemispheres are almost mirror images of each other — these are rings with a diameter of about 4 thousand km around each pole. In the Middle Ages, when the north magnetic pole was located to the east, the aurora was often visible in Scandinavia, northern Russia and northern China. The chroniclers of that time explained this by the fact that it was giants fighting in the sky, or that spears sparkling with multi-colored lights were flying from heaven to earth. Now the northern lights can often be observed in Scotland, especially in April; it appears about four times a year in northern Florida, but it is most clearly visible near the magnetic poles: for example, in northern Canada and in the Ross Trench in Antarctica. One of the most convenient places is Northern Scandinavia; It is good to observe the aurora on the island of Svalbard, north of Norway. And the aurora borealis is best observed on the Antarctic continent. The auroras are also observed from space, where, among other things, there is no distorting influence of the lower dense layers of the atmosphere. Observations from manned spacecraft and orbital stations have provided rich material on the spatial arrangement of auroras, their change in time, and many features of this phenomenon. Moreover, spacecraft have made it possible to take measurements inside the aurora. Auroras can also be observed on the day side of the Earth in this way.
It is safe to say that research in recent decades, including the study of the phenomenon from artificial Earth satellites and rockets and the creation of artificial auroras, has significantly enriched our knowledge of the northern lights. It is clear that not only the riddle of the northern lights has been unraveled, but also a large amount of factual material has been accumulated about the space surrounding our planet, the state of the interplanetary medium and solar radiation, including fluxes of charged particles. And yet the problem of the northern lights is still far from being solved. Indeed, we know that this is a glow of the upper atmosphere at high latitudes of the northern and southern hemispheres of the Earth, caused by energetic charged particles invading the Earth’s magnetosphere on their way from the Sun. The main regularities of the manifestation of the northern lights are also known: their dependence on height, geographical location, solar activity, perturbations of the Earth’s magnetic field, etc. And yet, at the present time, we still cannot not only describe quantitatively this phenomenon, but even predict in advance many of the regularities of the forthcoming northern lights. The problem of northern lights is too complex and multifaceted. For example, the connection between the northern lights and the weather is still unclear. Northerners are well aware that the northern lights are more often observed on frosty nights. There is no explanation for this yet. At the same time, unexpected relationships are emerging, waiting for their future researchers, in rather unusual questions. Is it only the fear of incomprehensible impressive natural phenomena that underlies these superstitions? It is now well known that solar rhythms with different periods (27 days, 11 years, etc.) affect the most diverse aspects of life on Earth. Solar and magnetic storms (and the associated northern lights) can cause an increase in various diseases, including diseases of the human cardiovascular system. Changes in the climate on Earth, the occurrence of droughts and floods, earthquakes, etc. are associated with solar cycles. All this makes us once again seriously think about the connection between the northern lights and earthly cataclysms and troubles. Maybe the old ideas about such a connection are not so stupid? The northern lights signal the place and time of the impact of the Cosmos on earth processes. The invasion of charged particles that causes them affects many aspects of our lives. The ozone content and the electric potential of the ionosphere change, the heating of the ionospheric plasma excites waves in the atmosphere. All this affects the weather. Due to additional ionization in the ionosphere, significant electric currents begin to flow, the magnetic fields of which distort the Earth’s magnetic field, which directly affects the health of many people. Thus, through the northern lights and the processes associated with them, the Cosmos affects the nature around us and its inhabitants.