Moon rainbow

What you may see is the aurora, which 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.

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 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 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 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.

Aurora often appears in the atmosphere above the latitude near the geomagnetic pole. Generally, they are in the form of belts, arcs, curtains and radiations, and these shapes are sometimes stable and sometimes continuously changing. Aurora is produced by the charged high-energy particle flow "up to 1 billion electron volts" in the solar active region, which excites or ionizes molecules or atoms in the upper atmosphere. Due to the geomagnetic field, these high-energy particles turn to the polar regions, so aurora is very common in high magnetic latitudes. Aurora often appears in the range of about 25-30 from the magnetic pole, which is called the aurora area. The area between 45 and 60 degrees of geomagnetic latitude is called weak auroral zone, and the area below 45 degrees of geomagnetic latitude is called micro auroral zone. The lower boundary height of aurora is less than 100 km from the ground, and the maximum light height is about 1 10 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 the 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. As early as more than 2,000 years ago, China began to observe the aurora, which has a rich aurora record.

Aurora is a dazzling light image that crosses the North and South poles. 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. The aurora that appears at this time is the most magnificent.

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. 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.