Aurora is a colorful plasma phenomenon that occurs when charged particles from the sun (solar wind) enter the Earth's magnetic field, creating a brilliant and beautiful glow at night in the high altitude near the Earth's north and south poles. It is called the Aurora Australis in Antarctica and the Aurora Borealis in the Arctic. The aurora of the Earth is generated by high-energy charged particle flows (solar winds) from the Earth's magnetosphere or the Sun, which excite (or ionize) molecules or atoms in the upper atmosphere. Auroras often appear over areas near the geomagnetic poles at latitudes, usually in the form of bands, arcs, curtains, or radiations, which are sometimes stable and sometimes undergo continuous changes. There are three conditions for the generation of auroras: atmosphere, magnetic field, and high-energy charged particles. Modern physics provides a detailed description of the principle behind auroras. Auroras on Earth emit light due to charged high-energy particles from the magnetosphere and solar wind being guided into the Earth's atmosphere by the geomagnetic field and colliding with atoms in the upper atmosphere (thermosphere). Auroras not only appear on Earth, but also on other planets with magnetic fields in the solar system
Aurora is a phenomenon of light emitted by an electric explosion at an altitude of 80-500 kilometers. The strong magnetic field formed by the "magnetic south pole" and "magnetic north pole" of the Earth moves in a spiral motion along an arc-shaped magnetic field line towards the two poles, causing several gases in the atmosphere above the poles to emit light. [28]
According to research on the distribution of auroras, the shape of the auroral region is not a circular ring centered on the geomagnetic pole, but an oval shape. The spectral line range of aurora is about 3100-6700 angstroms, with the most important spectral line being the oxygen atom green line at 5577 angstroms, known as the aurora green line.
Most auroras appear 90 to 130 kilometers above the Earth. In 1959, an aurora borealis measured an altitude of 160 kilometers and a width exceeding 4800 kilometers. But some auroras are much higher, reaching heights of over 560-1000 kilometers.
Due to the effect of the geomagnetic field, these high-energy particles turn towards the polar region, so auroras are common in high magnetic latitude areas. Aurora often appears within a range of approximately 25 ° to 30 ° from the magnetic pole, and this area is called the aurora zone. The range of geomagnetic latitude between 60 ° -90 ° is called the aurora zone, the area between 45 ° -60 ° is called the weak aurora zone, and the area below 45 ° is called the micro aurora zone.
Basic classification
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Auroras can be divided into two types based on their properties: diffused auroras and discrete auroras. Even in a dark sky, the naked eye may not be able to see the faint light and shape emitted by the diffuse aurora, but it defines the range of the aurora band.
Discrete auroras are parts of the diffuse aurora that are almost invisible and can be clearly seen with the naked eye. They are bright enough to read books and newspapers at night. But discrete auroras can only be seen in the night sky because their brightness is not enough to appear in sunlight. Auroras typically appear as diffuse spots or arcs in the aurora band, and are typically visible to the naked eye. Discrete auroras typically display magnetic field lines or curtain like structures, with the most common being green fluorescence, which can change within seconds or remain unchanged in brightness for several hours.
According to the morphology of auroras, they can be classified into uniform arc auroras, radial column auroras, radial arc band auroras, curtain shaped auroras, auroral crowns, etc.
According to the electromagnetic wave bands observed by auroras, they can be divided into optical auroras, radio auroras, etc.
According to the type of laser excited particles, it can be divided into electron aurora, proton aurora, etc.
According to the region of aurora occurrence, it can be divided into polar cover aurora, aurora strip aurora, mid latitude aurora red arc, etc.
The modern trend guides and recommends distinguishing aurora phenomena by comparing meteorology, but it has not yet been fully recognized
Auroras appear over high latitude regions of the planet, and are a colorful glowing phenomenon. And the auroras of the Earth, generated by high-energy charged particle flows (solar winds) from the Earth's magnetosphere and the Sun, excite (or ionize) molecules or atoms in the upper atmosphere. There are three conditions for the generation of auroras: atmosphere, magnetic field, and high-energy charged particles. These three are indispensable. Auroras not only appear on Earth, but also on other planets with magnetic fields within the solar system.
Auroras usually only appear in high latitude areas at the north and south poles, but on August 1, 2010, a solar storm erupted facing the Earth, carrying a large number of charged particles. The solar wind accurately "hit" the Earth, interacting with the Earth's magnetic field to produce a "magnetic storm", allowing slightly lower latitude areas such as Michigan, Denmark, and the United Kingdom to see beautiful views of the Northern Lights. Experts say that this solar storm did not destroy global satellites and telecommunications systems as previously speculated, but instead brought a magnificent "fireworks display" to Earth
Aurora is a large-scale discharge process around the Earth. Charged particles from the sun reach the vicinity of the Earth, and the Earth's magnetic field forces a portion of them to concentrate along the magnetic field lines to the north and south poles. When they enter the upper atmosphere of the polar region (greater than 80km), they collide with atoms and molecules in the atmosphere and are excited, releasing energy to produce light that forms a large circle around the magnetic poles, known as aurora.
The period when auroras are most likely to appear is before the arrival of the spring and autumn equinoxes, and the frequency of occurrence in spring and autumn is even higher than that in summer and winter. This is because during the Spring Equinox and Autumn Equinox, the Earth's position is most intertwined with the magnetic flux. In addition, when there are many sunspots or when the solar cycle is in the stage of increased coronal ejection and solar wind intensity, the frequency and brightness of auroras will also increase. [8]
Modern perspectives
Many scientists are conducting in-depth research on auroras. The auroras that people see are mainly caused by electrons in charged particle flows. Moreover, the color and intensity of auroras also depend on the energy and quantity of settling particles. To use a vivid analogy, it can be said that auroral activity is like a live television screen of magnetospheric activity. The settling particles are the electron beam of the television, the Earth's atmosphere is the television screen, and the Earth's magnetic field is the electron beam guiding magnetic field. Scientists have obtained a wealth of information on the magnetosphere and electromagnetic activities in the solar Earth space from this natural large television. For example, through auroral spectroscopy analysis, we can understand the source, particle type, energy size, structure of the Earth's magnetic tail, interaction between the Earth's magnetic field and planetary magnetic field, as well as the way and degree of solar disturbance affecting the Earth.
Although auroras are beautiful, the energy they project into the Earth's atmosphere can be compared to the total amount of capacitance produced by power plants in various countries around the world. This energy often disrupts the signals of radio and radar. The strong current generated by auroras can also accumulate on long-distance telephone lines or affect the propagation of microwaves, causing partial or complete loss of current in circuits, and even causing serious interference to power transmission lines, resulting in temporary loss of power supply in certain areas. How to utilize the energy generated by auroras for the benefit of humanity is an important mission in the scientific community today.
Electromagnetic ion cyclotron waves are a typical microscale wave that often interact with charged particles through cyclotron resonance. One of the results of this interaction is the deposition of charged particles in space into the Earth's atmosphere, which can also generate phenomena such as auroras through subsequent processes.
Aurora is a large-scale discharge process around the Earth. Charged particles from the sun reach the vicinity of the Earth, and the Earth's magnetic field forces a portion of them to concentrate along the field line to the north and south poles. When they enter the upper atmosphere of the polar regions, they collide and excite with atoms and molecules in the atmosphere, producing light and forming auroras. A common occurrence is in two circular areas near 67 degrees north and south latitude, with Fairbanks in Alaska experiencing over 200 days of aurora each year, hence it is known as the "Northern Aurora Capital". So auroras can only be seen at the north and south poles of the Earth.
The magnetic field lines in the Earth's magnetosphere carry the energy of the solar wind into the Earth's interior, which in turn drives the formation of the geomagnetic field. In addition to the conductive body inside the Earth, there is also the weak conductive body of the ionosphere in the atmosphere on this closed loop of magnetic field lines in the magnetosphere. When the solar wind is strong, the energy of the magnetic field lines encounters the magnetic impedance inside the Earth, and a lot of energy cannot be consumed, thus forming auroras at the ionosphere.
The appearance of multiple colors is due to the intense solar activity, and it is also directly related to the collision of high-energy particles released by the sun with different atoms in the atmosphere, such as oxygen and nitrogen atoms
The Beauty of Aurora
Aurora is considered one of the most beautiful wonders in nature. As early as over 2000 years ago, China began observing auroras and has rich records of them. Auroras are diverse, colorful, and of varying shapes, incredibly beautiful, and there is no phenomenon in nature that can rival them. It is difficult for any colored pen to draw the dazzling light that frolicks and changes in the extreme cold air. Auroras sometimes appear for a very short time, like festive fireworks flashing in the air and disappearing without a trace; Sometimes it can shine for hours in the sky; Sometimes it's like a ribbon, sometimes it's like a ball of fire, like a colorful giant screen, as if a ball screen movie is being released, giving people a visual enjoyment of beauty. If we travel in a spacecraft over the North and South Poles of Earth and look at the Earth from afar, we will see a shining halo around the Earth's magnetic poles, which is called an aurora egg. Due to their slightly flattened side towards the sun and slightly stretched side away from the sun, they take on an egg like shape. The aurora egg is constantly changing, sometimes bright and sometimes dark, sometimes extending towards the equator, and sometimes contracting towards the poles. The halo at midnight appears the widest and brightest.
Long term observation statistics indicate that the most common locations for auroras are in the two circular regions near the north and south magnetic latitudes of 67 degrees, known as the Antarctic and Northern Aurora regions, respectively. Aurora activity occurs almost every day within the aurora zone. In the internal area surrounded by the aurora egg, usually called the polar cover area, the chances of aurora appearing in this area are actually less than in the lower latitude aurora area. In mid to low latitude regions, especially near the equator, auroras are rarely observed, but it does not mean that auroras cannot be observed at all. On the night of February 10, 1958, a massive aurora was visible in the tropics and displayed a bright red color. These types of auroras are often associated with large solar flares and strong geomagnetic storms. In the cold polar regions, people look up at the night sky and often see auroras of various shapes and colors. It is no exaggeration to say that there is simply no two identical aurora shapes in the world. From the perspective of scientific research, people divide the aurora into five types according to its morphological characteristics: one is the arc shaped aurora arc with neat and slightly curved bottom; The second is the curved and wrinkled ribbon shaped aurora band; The third is the cloud like patches of aurora; The fourth is the uniform tent like aurora mantle like a veil; The fifth is a radial aurora along the direction of magnetic field lines.
The brightness of the auroral form also varies greatly, from the brightness of the just visible Milky Way nebula to the brightness of the moon at full moon. When strong auroras appear, the contours of objects on the ground can be illuminated, even casting shadows on them. The most touching thing, of course, is the ever-changing and wonderful scene caused by the aurora movement. We often describe things as becoming faster and say, "In the blink of an eye, an old hen turns into a duck." Auroras are like this, turning hands into clouds and covering hands into rain, unpredictable, and all of this often happens within seconds or minutes. The movement and changes of auroras are a play of light staged by the master of magic in nature, using the sky as a stage. There are hundreds or even thousands of kilometers of aurora bands running up and down, and even nearly ten thousand kilometers long. This magnificent and spectacular natural scenery seems to be imbued with a touch of fairy charm, and is quite mysterious. What is breathtaking is the colors of the aurora, which can no longer be described with colorful colors. At the end of the day, its true colors are nothing more than red, green, purple, blue, white, and yellow. However, nature, as a super painter, uses ingenious techniques to combine depth, intensity, and subtle light and dark, making it a kaleidoscope.
According to incomplete statistics, there are over 160 distinct auroral tones that can be distinguished. The aurora is so colorful and ever-changing, amidst such vast and boundless domes, pitch black and silent cold nights, and uninhabited polar regions. At this moment, facing the colorful aurora patterns, dear reader, can you say that it is not intoxicating or enchanting? No wonder in the notes of many polar explorers and travelers, describing auroras often appears to be exhausting, with only words like "indescribable" and "unable to find suitable words to describe" used as excuses. Yes, ordinary words such as beauty, grandeur, and wonder appear exceptionally pale and powerless in front of the aurora. It can be said that even with clever writing, it is difficult to describe the aura, momentum, and temperament of the aurora.
Magical Sound
Aurora Borealis refers to the luminous phenomenon that often occurs in the upper atmosphere of high latitude regions on Earth, and is the result of the interaction between the solar wind and the Earth's magnetic field. The aurora borealis is very brilliant and beautiful, and what accompanies it is a very mysterious sound.
Throughout history, there have been many legends circulating about the mysterious sound of the Northern Lights, which has also made people in the wilderness feel fear and awe.
The source of this ambiguous burst sound emitted by the Northern Lights has finally been scientifically explained for the first time.
Scientists at the University of Alto in Finland have discovered the Aurora Borealis god
Scientists at the University of Alto in Finland have discovered the source of the mysterious sound of the Northern Lights, which is produced in the air at a height of 70 meters above the ground. In contrast, the dazzling and unpredictable aurora borealis generated by the interference of the Earth's magnetic field occurs at an altitude of 120 kilometers above the ground.
In order to find the source of the sound, scientists used three independent microphones to record the sound of the Northern Lights at observation points. Subsequently, scientists compared and analyzed these sounds to ultimately determine the source of the Northern Lights sound. When the Northern Lights appeared at the observation point, the Finnish Meteorological Institute also synchronously measured the geomagnetic interference caused by the Northern Lights.
Professor Unto K. Laine from the University of Alto said, "Our research has found that during the appearance of the Northern Lights, people can hear a natural sound that accompanies them. In the past, we believed that the aurora was too far away from us to hear the sound emitted by the aurora, and this inference was correct. However, the fact is that the aurora is generated by energy particles generated by the sun interfering with the Earth's magnetic field. They are located far away in the sky, and the sound accompanying the aurora is also produced for similar reasons, but the place where this sound is produced is closer to the ground."
The specific reason for the mysterious sound of the Northern Lights is still a mystery, and this sound is not always accompanied by the Aurora. From the recorded sound, it sounds like a vague popping sound, often lasting only for a short period of time. Some people who have heard the sound of auroras describe it as a crackling sound and feel that the sound is far away. Through these different descriptions, scientists speculate that there may be several different principles behind the sound produced by the Northern Lights.
