Aurora events in the history of China

Aurora hangs high in the sky near the north and south poles of the earth and often looks bright and beautiful at night. It floats lightly and flashes at the same time, emitting red, blue, green and purple light. This magnificent and moving sight is called aurora. In the high altitude areas near the north and south poles of the earth, brilliant and beautiful glow often appears at night. It floats lightly and flashes at the same time, emitting red, blue, green and purple light. This magnificent and moving sight is called aurora.

Aurora is diverse, colorful, different in shape and incomparable in beauty, and nothing in nature can match it. It is difficult for any marker to draw that unpredictable dazzling light in the cold Arctic air.

Aurora sometimes appears for a short time, just like the fireworks of the festival flashed in the air and disappeared without a trace; Sometimes it can shine in the sky for hours; Sometimes like a ribbon, sometimes like a flame, sometimes like a colorful giant screen; Some colors are changeable and endless; Some are just silvery white, like cotton wool and white clouds, solidified; Some of them are unusually bright, covering up the brilliance of the stars and the moon; Some are very light, like a bunch of moss; Some structures are simple, like a curved arc, showing a light green and reddish tone; Some are like colored silks or ribbons thrown into the sky, flying up and down; Some are as soft as scarves, fluttering in the wind, showing purple and crimson colors; Sometimes the aurora appears on the horizon, just like the morning light; Sometimes it is as bright as camellia and red; Sometimes the aurora gathers together, just like a curtain; Sometimes it shoots many beams, just like a proud peacock, flying with butterfly wings.

How is the aurora produced? For centuries, this has been a mystery of astronomical phenomena that people have speculated and explored. Once upon a time, Eskimos thought it was a torch of ghosts and gods, guiding the souls of the dead to heaven. /kloc-in the 0/3rd century, people thought it was the light reflected by the Greenland ice sheet. It was not until the17th century that people called it the Northern Lights-Arctic Dawn (the same light seen in the South Pole is called the Southern Lights).

With the progress of science and technology, the mystery of aurora is more and more known to us. It turns out that this beautiful scenery is the work of cooperation between the sun and the atmosphere. Among the forms of energy created by the sun, such as light and heat, one is called "solar wind". The solar wind is charged particles ejected by the sun, and it is a powerful stream of charged subatomic particles, which can cover the earth. The solar wind flows around the earth over the earth and hits the earth's magnetic field at a speed of about 400 kilometers per second. The earth's magnetic field is shaped like a funnel, with its tip facing the north and south poles of the earth, so charged particles emitted by the sun settle along the "funnel" of the earth's magnetic field and enter the polar regions of the earth. The upper atmosphere of the poles, bombarded by the solar wind, will glow and form aurora. What is formed in the Antarctic region is called Antarctic light. What is formed in the North Pole is called the Northern Lights.

1890, Norwegian physicist birkeland thought that the sun, which is 0/500,000 kilometers away from the earth/kloc-0, almost continuously radiates material points to the earth. However, from 50000 km to 65000 km away, there is a magnetic field covering the earth. When the sun's particles are directly blocked by this magnetic field, it will spread around the earth, looking for the drilled gap. As a result, about 65,438+0% of the particles got into the atmosphere near the north magnetic pole. Each solar particle contains electricity equal to 1000 volts. They encounter atoms and molecules mainly composed of oxygen and nitrogen in the upper atmosphere 100 km away. When atoms absorb part of the energy contained in solar particles, they will immediately release this energy, thus producing extremely intense light. Oxygen emits green and red light, while nitrogen emits purple, blue and some crimson light. These colorful colors make up a beautiful and spectacular aurora scene.

At present, many scientists are conducting in-depth research on aurora. The aurora seen by people is mainly caused by electrons in the charged particle flow. Moreover, the color and intensity of aurora also depend on the energy and quantity of settling particles. Using an image metaphor, it can be said that aurora activity is like a live TV picture of magnetosphere activity. Sedimentation particles are the electron beam of TV, the earth's atmosphere is the TV screen, and the earth's magnetic field is the electron beam guiding magnetic field. Scientists got a lot of information about the magnetosphere and the electromagnetic activities in the solar-terrestrial space from this nature TV. For example, through polarographic analysis, we can know the source, particle type, energy, the structure of the earth's magnetic tail, the interaction between the earth's magnetic field and the planetary magnetic field, and the way and degree of the influence of solar disturbance on the earth.

Aurora is not only beautiful, but also the energy cast in the earth's atmosphere can be compared with the total capacity generated by power plants all over the world. This energy often confuses radio and radar signals. The strong current generated by aurora can also gather on long-distance telephone lines or affect the propagation of microwaves, so that some or all of the current in the circuit is "lost", and even the transmission lines are seriously disturbed, thus temporarily losing power supply in some areas. How to use the energy generated by aurora to benefit mankind is an important mission of today's scientific community.

Second, the aurora events observed in the history of China

Aurora is a phenomenon that charged particles from the sun collide with the magnetic fields at the poles of the earth and discharge in the sky. The sun is a huge and hot gas ball, and the nuclear reactions of various chemical elements are carried out inside and on its surface, resulting in a powerful stream of charged particles, which are emitted from the sun and shot into the surrounding space at a very high speed. When this charged particle stream shoots into the thin upper atmosphere around the earth, it collides violently with the molecules of the thin gas, resulting in a luminous phenomenon, which is aurora. These colorful lights in the night sky are common in high latitudes near the north and south poles. On a clear summer night, you can sometimes see the aurora in low latitudes far away from the city lights. On the border between Canada and the United States, you can see the Northern Lights on many nights every year. The northern lights or the southern lights are as charming as fireworks. The colors of aurora vary from light green to deep red. Some of them are like colored paper ribbons, some are like bows, some are like curtains, and some are like shells.

In the high altitude areas near the north and south poles of the earth, brilliant and beautiful glow often appears at night. Sometimes it is like a ribbon, sometimes it is like a flame, and sometimes it is like a colorful giant screen. It floats lightly and flashes at the same time, emitting red, blue, green and purple light. The silent polar region suddenly appears full of vitality because of its appearance. This magnificent and moving sight is called aurora.

Aurora has been known for at least 2000 years, so it has been the theme of many myths. In the early Middle Ages, many people thought Aurora was a warrior riding a horse across the sky. In the Arctic, Inuit believe that the aurora was created by God to light the way for the newly dead. With the progress of science and technology, the mystery of aurora is more and more known to us. It turns out that this beautiful scenery is the work of cooperation between the sun and the atmosphere.

Aurora is produced by high-energy particles (electrons and protons) outside the atmosphere hitting atoms in the upper atmosphere. This interaction often occurs in the area around the earth's magnetic pole. It is now known that charged particles, as a part of the solar wind, are captured by the earth's magnetic field when they reach the vicinity of the earth, and make them fall towards the magnetic pole. They collide with oxygen atoms and nitrogen atoms, knocking out electrons and turning them into excited ions. These ions emit radiation with different wavelengths, producing the characteristic colors of aurora such as red, green or blue. At the peak of solar activity, the aurora sometimes extends to the mid-latitude zone. For example, in the United States, the Northern Lights can be seen south of 40 degrees north latitude. Aurora has many shapes, such as curtain, arc, band and ray. The arc-shaped aurora with uniform light emission is the most stable shape, which sometimes lasts for several hours without obvious change. However, most other shapes of aurora usually change rapidly. The contour of the lower edge of arc and folded aurora is usually more obvious than that of the upper end. Finally, the aurora recedes to the polar regions, and the glow gradually disappears in the diffuse white sky. The mechanism that causes the dynamic change of aurora is still completely clear. Among the forms of energy created by the sun, such as light and heat, one is called "solar wind". This is a powerful stream of charged subatomic particles, which can cover the earth. The solar wind flows around the earth over the earth and hits the earth's magnetic field at a speed of about 400 kilometers per second. The magnetic field deflects the particle flow to the earth's magnetic pole, thus causing the charged particles to chemically react with the upper atmosphere of the earth to form aurora. What is formed in the Antarctic region is called Antarctic light. This phenomenon can also be seen in the Arctic, commonly known as the Northern Lights.

Most auroras appear at 90- 130 km above the earth. But some auroras are much higher. 1959, the height measured by the Northern Lights at one time was 160 km, and the width was over 4800 km. City lights and high-rise buildings on the horizon may prevent us from seeing light, so the best aurora can only be observed in the open areas of the countryside. In Churchill, Canada, you can see the aurora 300 nights a year; In Florida, you can only see it four times a year on average. Mohe in the northernmost part of China is also a good place to watch the aurora.

/kloc-in the middle of the 8th century, scientists from a geophysical observatory in Sweden found that when the observatory observed the aurora, the compass pointer on the ground would change irregularly, with the change range as much as 1 degree. At the same time, a similar phenomenon was recorded at the geomagnetic station in London. Therefore, they believe that the appearance of aurora is related to the change of geomagnetic field. It turns out that the aurora is the result of the interaction between the solar wind and the earth's magnetic field. The solar wind is charged particles ejected by the sun. When it blows over the earth, it will be affected by the earth's magnetic field. The earth's magnetic field is shaped like a funnel, with its tip facing the north and south poles of the earth, so charged particles emitted by the sun settle along the "funnel" of the earth's magnetic field and enter the polar regions of the earth. The upper atmosphere of the poles, bombarded by the solar wind, will glow and form aurora. The upper atmosphere is composed of many gases, and the front colors of light emitted by gases with different elements are different after being bombarded. For example, when oxygen is excited, it emits green light and red light, when nitrogen is excited, it emits purple light, and when argon is excited, it emits blue light, so the aurora appears colorful and varied.

Scientists have learned that the earth's magnetic field is asymmetric. Driven by the solar wind, it becomes a "streamline". That is to say, the magnetic lines of force towards the sun are greatly compressed, but in the opposite direction, a tail-like magnetic tail of the earth is pulled out. The length of the magnetic tail is at least 1 0,000 of that of radius of the earth. Due to the coupling effect with the interplanetary magnetic field in the sun-earth space, the shape of the two poles of the deformed earth's magnetic field has become a narrow polar region with weak magnetic field strength. Because plasma has the characteristic of "freezing" magnetic field lines, solar wind particles can't cross the earth's magnetic field, but can only enter the earth's magnetic tail through the pole tip. When the solar activity changes dramatically (such as flare explosion), geomagnetic substorms are often caused. So these charged particles are accelerated and move along the magnetic field lines. These charged particles are injected into the earth from the polar regions and hit gas molecules and atoms in the upper atmosphere, making the latter excite-de-excite and emit light. Different molecules and atoms produce different colors of light, and these monochromatic lights are mixed together to form colorful aurora. In fact, the aurora seen by people is mainly caused by electrons in the charged particle flow. Moreover, the color and intensity of aurora also depend on the energy and quantity of settling particles. Using an image metaphor, it can be said that aurora activity is like a live TV picture of magnetosphere activity. Sedimentation particles are the electron beam of TV, and the earth's atmosphere is the TV screen. The earth's magnetic field is an electron beam-guided magnetic field. Scientists got a lot of information about the magnetosphere and the electromagnetic activities in the solar-terrestrial space from this nature TV. For example, through polarographic analysis, we can know the source, particle type, energy, the structure of the earth's magnetic tail, the interaction between the earth's magnetic field and the planetary magnetic field, and the way and degree of the influence of solar disturbance on the earth.

The formation of aurora is closely related to solar activity. In the most active year of solar activity, you can see more spectacular aurora scenes than usual. Aurora can also be seen in many areas where it was not seen before at low latitudes. On the night of April 6, 2000, aurora appeared in northern Europe and America. Aurora has appeared in the northern hemisphere of the earth, even in Florida in the southern United States and south-central Germany. That night, red, blue and green light filled the night sky, and the scene was spectacular. Although this is a rare blessing, gorgeous colors suddenly appeared in the plain sky in the past, causing panic in many areas. According to kaminsky, director of Bochum Observatory in Germany, the telephones of police stations and observatories in the northern part of the Rhine River in Germany kept ringing that night, and some even suspected that there was another gas leak. This aurora phenomenon was discovered by the spacecraft ACE observing the sun at a height of 160 km, and a warning was issued. At 0: 30 am on April 7th, Beijing time, the spacecraft ACE discovered a solar wind, and powerful charged particles passed by it. The solar wind suddenly accelerated from 375 kilometers per second to 600 kilometers per second. An hour later, the solar wind reached the outer edge of the earth's atmosphere, showing us a rare miracle.