What harm will the solar wind do if it comes to the earth?

Solar wind is a supersonic plasma (charged particles) stream emitted from the upper atmosphere of stars. When it is not the sun, this flow of charged particles is usually called "stellar wind".

At the high temperature of the solar corona (millions of Kelvin), atoms such as hydrogen and helium have been ionized into positively charged protons, helium nuclei and negatively charged free electrons. These charged particles move so fast that they break away from the gravitational bondage of the sun and shoot to the periphery of the sun, forming the solar wind. The speed of the solar wind is generally 200-800 km/s, and it is generally believed that during the minimum period of solar activity, the high-speed solar wind blows from the polar region of the solar magnetic field and the low-speed solar wind blows from the equatorial region of the solar magnetic field. The activity of the solar magnetic field will change, with a period of about 22 years.

The term solar wind was put forward by Parker in AD 1950. But it was not until A.D. 1960 that its existence was confirmed. Long-term observation shows that high-speed solar wind can be observed near the earth when coronal holes appear in the sun. Therefore, astronomers believe that the generation of high-speed solar wind is closely related to coronal holes. The magnetic field and plasma activity on the surface of the sun have great influence on the earth. When the solar activity is strong, a large number of charged particles blow to the poles of the earth with the solar wind, which will cause beautiful aurora in the ionosphere of the poles.

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In the solar system, the composition of the solar wind is exactly the same as that of the solar corona. 73% is hydrogen, 25% is helium and other trace impurities. At present, there is no accurate measurement result. The sampling analysis of Genesis in 2004 is still inconclusive. It was damaged by crash landing when it returned to Earth. This is because it did not open its parachute when it re-entered the earth's atmosphere.

Near the earth, the speed of solar wind is 200-889 km/s, with an average of 450 km/s, and about 800 kg/s of material escapes from the sun in the form of solar wind. This is very small compared with the equivalent mass of solar rays. If the energy of sunlight is converted into mass, the sun loses about 4.5 TG (4.5×10.9 kg) per second.

Because the solar wind is plasma, the solar magnetic field is carried by it. Due to the rotation of the sun, the solar magnetic field is pulled into a spiral shape by the solar wind. Usually, the energy burst of the solar wind comes from solar flares or other climatic phenomena called "solar storms". These solar activities can be detected by space probes and satellites, and the main sign is strong radiation. Solar wind particles captured by the earth's magnetic field are stored in the Van Allen radiation belt. When these particles interact with the earth's atmosphere near the magnetic pole, the aurora phenomenon is produced. Other planets with magnetic fields similar to the earth's also have auroras.

In interstellar medium (mainly thin hydrogen and helium), the solar wind seems to blow out a "big bubble". The place where the solar wind can't continue to push the interstellar medium is called the zenith, which is usually considered as the outer boundary of the solar system. How far this boundary is from the sun has no definite result, and it may change according to the intensity of the solar wind and the density of the local interstellar medium. It is generally believed that it is far beyond Pluto's orbit.

[Edit] History

1958, Parker predicted that there should be a strong wind blowing out from the sun continuously, so that plasma would fill the interplanetary space. Before that, scientists thought this space was a vacuum. This discovery has changed scientists' view of interplanetary space forever, which can explain many phenomena, such as "magnetic storms" (which can paralyze the power supply network on earth) to the formation of distant stars.

In the 1930s, scientists knew that the sun's corona had a high temperature of several million degrees (degrees Celsius), which was calculated according to the protruding shape of the corona observed during the total solar eclipse. Some very clever spectral analysis work has also confirmed this high temperature. In 1950s, the British mathematician Sydney Chapman calculated the properties of gas at such a high temperature and such a good thermal conductor. He found that the corona must extend into space beyond the earth's orbit. Also in 1950s, German scientist Ludwig Biermann was interested in the direction of a comet's tail facing the sun, that is, whether it is facing the sun or far away from the sun, its tail always points away from the sun. He therefore speculated that the steady wind from the sun pressed the tail to produce this phenomenon.

Parker realized that in Chapman's model, the outward radiation of heat from the sun should be the same phenomenon as beermann's hypothesis of comet tail. Parker proved that the corona is a good conductor of heat even if it is bound by the strong solar gravity. The corona will stay hot far away from the sun. This is because gravity decreases with the increase of distance, so the solar atmosphere in the outer layer of the corona will escape into space.

At that time, the opposition to Parker's solar wind hypothesis was very strong. His paper submitted to the Journal of Astrophysics was rejected by two reviewers. But later editor subrahmanyan chandrasekhar (later won the 1983 Nobel Prize in Physics) kept this paper.

In the 1960s, this solar wind hypothesis was confirmed by direct satellite observation. This hypothesis explains geomagnetic storms, auroras and other solar and earth phenomena.