Aurora is diverse, colorful, different in shape and incomparable in beauty, and nothing in nature can match it. It is difficult for any mark to draw that unpredictable dazzling light in the cold polar 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, 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 like a curtain; Sometimes it shoots many beams, just like a proud peacock, flying with butterfly wings.
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 gradually revealed. It turns out that this beautiful scenery is a work of cooperation between the sun and the atmosphere. Among the various forms of energy created by the sun, such as light and heat, one kind of energy 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, hitting the earth's magnetic field at a speed of about 400 km/s. The earth's magnetic field is shaped like a funnel with its tip facing the north and south poles of the earth, so the 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 Southern Lights, and what is formed in the Arctic region is called Northern Lights.
Scientifically, the area with geomagnetic latitude lower than 45 is called micro-aurora area. The lower boundary height of aurora is less than 100 km from the ground, and the maximum luminous height is about 1 100 km. The normal maximum boundary is about 300 km, and in extreme cases it can reach more than 1000 km. According to the research on the distribution of aurora in recent years, the shape of aurora is not a ring with the geomagnetic pole as the center, but more like an ellipse. The spectral range of aurora is about 3 100 ~ 6700 angstroms, and the most important spectral line is the oxygen atom green line of 5577 angstroms, which is called the aurora green line.
1890, when Norwegian physicist birkeland analyzed the causes of aurora, he thought that the sun, which is 0/500,000 kilometers away from the earth, almost continuously radiated material points to the earth. However, there is a magnetic field covering the earth at a distance of 50,000 ~ 65,000 kilometers. When the sun's particles are blocked by this magnetic field, it will spread around the earth, looking for holes to be drilled. 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 energy and produce 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.
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. Up to now, no one knows exactly the cause of the aurora, but people usually think that the aurora is the result of the deflection of tiny high-energy particles from the sun after the earth's magnetic field is blocked. One is the glow produced by the collision of solar high-energy particles with oxygen and nitrogen atoms in the outer atmosphere of the earth under the action of the earth's magnetic field. The sun has a very active cycle every 1 1 year, emitting a large number of high-energy particles into space. How to use the energy generated by aurora to benefit mankind is an important mission of today's scientific community.
Because city lights and high-rise buildings on the horizon may prevent us from seeing light, 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 about four times a year on average. 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.
There is no absolute latitude requirement to see the aurora, because strong aurora can be seen in south-central China, but it is very rare. But generally speaking, China is at a disadvantage in observing the aurora, because the north magnetic pole is biased towards the North American continent, so it is also 40 north latitude. The magnetic latitude of Pittsburgh in the United States is much higher, which is much more likely to see the aurora than Beijing.
Aurora is so beautiful, is it a unique patent of the earth? In the past, scientists used NASA's Hubble Space Telescope to accidentally take photos of Jupiter's aurora. However, using the infrared telescope of the Southern European Observatory, scientists can observe the aurora of Jupiter and the smoke over the North Pole more clearly.
Scientists point out that the aurora is around Jupiter's magnetic axis, and the smoke is around Jupiter's axis of rotation, but below the polar ring. The smoke is influenced by the zonal wind on Jupiter, which moves at the same latitude. Scientists believe that Jupiter's rapid rotation at 10 hour will also affect the movement of smoke over the poles.
It is observed that the brightness of the aurora also changes greatly, from the brightness of the Milky Way nebula that can be seen just now to the brightness of the moon at the full moon. When strong aurora appears, you can see the outline of objects on the ground and even reflect the shadow of objects. Of course, the most touching thing is of course the ever-changing wonderful scene brought by the aurora movement. When we describe how things change rapidly, we often say, "In the blink of an eye, an old hen turned into a duck." Aurora is really like this, turning hands into clouds, turning hands into rain, unpredictable, and all this often happens in a few seconds or minutes. The movement and change of aurora is a vivid drama staged by nature, a magic master. With the sky as the stage, there are hundreds of meters of Qian Qian and even nearly 10,000 kilometers of aurora. This magnificent natural scene, as if a little more fairy, is quite mysterious.
What is amazing is that the color of the aurora can no longer be described by colorful colors. In the final analysis, its true colors are nothing more than red, green, purple, blue and yellow, but the super painter of nature has turned the shades and hidden light and shade into a kaleidoscope with superb skills. According to incomplete statistics, there are more than 60 kinds of aurora tones that can be distinguished clearly at present.
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: 30am 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 375km/s to 600km/s. An hour later, the solar wind reached the outer edge of the earth's atmosphere, showing us a rare natural miracle.
solar wind
Solar wind is a supersonic plasma charged particle stream emitted from the upper atmosphere of stars. When it is not the sun, this flow of charged particles is usually called "stellar wind".
Solar wind is a continuous plasma flow from the sun, which moves at a speed of 200 ~ 800 km/s. Although this substance is different from the air on the earth, it is not composed of gas molecules, but of simpler basic particles, such as protons and electrons, which are one level smaller than atoms, but the effect they produce when flowing is very similar to that of air flow, so it is called solar wind.