Solar wind reading summarizes the main content of this article.

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 elementary particles, such as protons and electrons, which are one level smaller than atoms, but the effects they produce when flowing are very similar to air, so it is called solar wind. Of course, compared with the density of the wind on the earth, the density of the solar wind is very, very thin and insignificant. Generally, in the interplanetary space near the earth, there are several to dozens of particles per cubic centimeter, while the density of headwinds on the earth is 268.7 billion molecules per cubic centimeter. Although the solar wind is thin, it blows much more violently than the wind on the earth. On the earth, the wind speed of typhoon 12 is more than 32.5 meters per second, but the wind speed of the solar wind is often kept at 350 ~ 450 kilometers per second near the earth, which is tens of thousands of times the wind speed of the earth, and can reach more than 800 kilometers per second at the most violent time. The solar wind is constantly ejected into space from the outermost corona of the solar atmosphere. This particle stream is ejected from the corona hole, and its main components are hydrogen particles and helium particles. The other is radiation when the sun is active, which is fast and has high particle content. This solar wind is called "disturbed solar wind". The disturbed solar wind has a great influence on the earth. When it reaches the earth, it often causes huge magnetic storms and strong auroras, and also produces ionospheric disturbances. The existence of solar wind provides convenience for us to study the relationship between the sun and the earth.

cause

In order to clearly express how the solar wind is formed, it is necessary to understand the stratification of the solar atmosphere.

Generally speaking, we divide the solar atmosphere into six layers, which are named from inside to outside: solar nucleus, radiation belt, troposphere, photosphere, chromosphere and corona layer. The radius of the solar core accounts for about a quarter of the radius of the sun, which concentrates most of the mass of the sun and is where more than 99% of the energy of the sun occurs. The photosphere is the bright round surface of the sun that we usually see, and all the visible light of the sun is emitted from the photosphere.

The corona is located in the outermost layer of the sun and belongs to the outer atmosphere of the sun, where the solar wind is formed and emitted.

Through the photos taken by satellites and space probes, it can be found that there are some long-term strip-shaped large-area dark areas in the corona. The X-ray intensity in these areas is much lower than that in other areas. They look like some holes in the corona, which we call coronal holes.

Coronal hole is an open area of solar magnetic field, where the magnetic field lines spread into space, and a large number of plasma flows outward along the magnetic field lines, forming a high-speed particle flow. The velocity of particle flow at the bottom of the coronal hole is about 16km per second, and it can reach more than 800km per second when it reaches the earth orbit. This high-speed plasma flow is what we call the solar wind.

After the solar wind broke out from the coronal hole, it soon blew around with the trapped solar magnetic field. Now we know that the solar wind can at least blow all over the solar system.

When the solar wind reaches the vicinity of the earth, it interacts with the dipole magnetic field of the earth, blowing back the magnetic lines of the earth's magnetic field. However, the magnetic pressure of the earth's magnetic field blocked the movement of the plasma stream, making it impossible for the solar wind to invade the earth's atmosphere and bypass the earth's magnetic field to move on. In this way, a cavity is formed, and the earth's magnetic field is contained in this cavity. At this time, the shape of the earth's magnetic field is like an egg, a big head and a small head.

However, when the sun has a sudden violent activity, the situation will change. At this time, the high-energy ions in the solar wind will increase, and these high-energy ions can invade the polar regions of the earth along the magnetic field lines. And discharge in the upper atmosphere of the earth's poles, producing gorgeous and spectacular aurora.

1850, a British astronomer named carrington observed sunspots and found a small flash on the surface of the sun, which lasted about 5 minutes. Carrington thought he happened to see a big meteorite fall on the sun.

A brief history of observation

In the 1920s, with the more sophisticated instruments for studying the sun, people found that this kind of "sunlight" was a common thing, and its appearance was often related to sunspots. For example, in 1899, American astronomer Hall invented the "solar spectrograph", which can be used to observe the light of a certain wavelength emitted by the sun. In this way, people can rely on hydrogen and light in the solar atmosphere.

Small flash is a very common thing. In places with dense sunspots, as many as 100 times a day can be observed, especially when sunspots "grow". Huge flashes like those seen by carrington are rare, and only happen a few times a year.

Sometimes, the flash happens right in the center of the sun's surface, so its explosion direction points to the earth. After such an explosion, strange things will appear on the earth again and again. For several days, the aurora will be very strong, sometimes even in temperate regions. The hands of a compass will be restless and swing wildly, so this effect is sometimes called "magnetic storm". With the progress of science and technology, the mystery of aurora is becoming more and more known to us. 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 above it 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. The tip is facing the north and south poles of the earth, so the charged particles emitted by the sun settle along the "funnel" of the geomagnetic field and enter the polar regions of the earth. The upper atmosphere of the poles will glow after being bombarded by the solar wind, forming aurora. What is formed in the Antarctic region is called Southern Lights, and what is formed in the Arctic region is called Northern Lights.

Before this century, this situation had no influence on mankind. However, in the 20th century, it was found that magnetic storms would affect radio reception and various electronic devices. As humans become more and more dependent on these devices, magnetic storms become more and more important. For example, during a magnetic storm, radio and television transmission will be interrupted and radar will not work.

Astronomers have studied the sun's flash more carefully and found that in these bursts, there is obviously hot hydrogen thrown far away, and some of it will be ejected into space against the great gravity of the sun. The nucleus of hydrogen is proton, so there is a proton cloud around the sun (and a few complicated nuclei). 1958+0958, American physicist Parker called this outward proton cloud "solar wind".

When protons flying to the earth reach the earth, most of them will be pushed away by the earth's own magnetic field. But some of them will enter the atmosphere, causing aurora and various electrical phenomena. The extraordinary explosion of a powerful proton cloud hitting the earth will produce a phenomenon called "solar storm", and then the magnetic storm effect will appear.

It is the solar wind that makes the tail of a comet. When a comet approaches the sun, the dust and gas around the star will be blown back by the solar wind. This effect has also been confirmed on satellites. Large and light satellites like Echo- 1 will be blown off the pre-calculated orbit by the solar wind.

Related influence

Although the solar wind is fierce, it will not blow to the earth. This is because the earth has its own umbrella-the earth's magnetic field. The earth's magnetic field shields the sun from the earth. However, there will still be a few molecules escaping from the net, although only a few; But it will still bring a series of harm to the earth. It will interfere with the earth's magnetic field and make the intensity of the earth's magnetic field change obviously. It will also affect the upper atmosphere of the earth, destroy the structure of the ionosphere of the earth, make it lose the ability to reflect radio waves without wires, and cause the interruption of our radio communication; It will also affect the chemical changes of the atmospheric ozone layer, which will be transmitted layer by layer until it reaches the earth's surface, causing abnormal changes in the earth's climate, and even further affecting the crust, triggering volcanic eruptions and earthquakes. For example, on July 1959 and 15, people observed that the sun suddenly emitted a huge flame (this is the wind source of the solar wind). A few days later, in July 2655, at the same time, the geomagnetic field was severely disturbed by the so-called "magnetic storm", and global communication was suddenly interrupted, making some planes and ships relying on compasses and radio navigation suddenly "blind" and "deaf".

The influence of the solar wind on the earth is only caused by the molecules that escape the net, which shows how powerful the solar wind is in the unobstructed interstellar space.

Where the solar wind meets the interstellar matter outside, a shock wave will be generated. It is said that Voyager 1 launched by 1977 encountered this kind of shock wave in 2003. The shock wave is about 128 billion kilometers away from the sun.

scientific research

A house whose windows are blown open by the wind can resist the attack of storms as a whole, but the wind that breaks through the windows will blow the house into a mess. The latest research shows that the earth's magnetic field is like a house prone to "rain leakage" in front of the solar wind, and its "rain leakage" will last for several hours, providing an opportunity for charged particles from the sun to enter the earth's atmosphere and disrupt communication and power systems.

In the latest issue of the British journal Nature, researchers at the University of California, Berkeley, published the results of this study. The researchers said that the new results will help to better predict the possible impact of bad "space weather" such as solar storms on the earth.

From time to time, a solar wind composed of charged particles is blown from the sun. If the solar activity becomes intense, so will the solar wind. The earth itself has a magnetic field extending to tens of thousands of kilometers in space, which can form a protective barrier against the solar wind. However, this obstacle is not without defects. As early as 196 1, Dr. Deng Gai of Imperial College London, London, England predicted that when the direction of the magnetic field contained in the solar wind is partially opposite to that of the earth's magnetic field, the process of "magnetic reconnection" of the two magnetic fields will lead to a gap in the earth's magnetic field protection barrier, so that the charged particles of the solar wind can take advantage of it. Other scientists later confirmed the existence of this gap, but scientists have been unclear whether this gap in the earth's magnetic field is intermittent or will remain open for a long time.

Frey of the University of California, Berkeley, said that he and his colleagues found for the first time that the gap in the earth's magnetic field would open for several hours with the help of NASA's image detector and the observation data of satellites belonging to the European-American cooperative "Cluster" project. According to their calculations, at the boundary of the earth's magnetic field barrier, which is about 60,000 kilometers away from the earth's surface, the gap area may be twice that of the earth, and the solar wind thus entering will eventually produce proton auroras equivalent to California's size in the ionosphere above the North Pole.

Scientific significance

The discovery of solar wind is one of the most important discoveries in space exploration in the 20th century. After nearly 40 years of research, the physical properties of the solar wind have been basically understood, but so far people still don't know how the solar wind originated and how it accelerated. How to provide plasma and energy to the solar wind is a long-term unsolved basic topic in the field of space physics.