What is solar wind? Charged particles of the solar wind
It can reach values up to 1.1 million degrees Celsius. Therefore, having such a temperature, the particles move very quickly. The Sun's gravity cannot hold them, and they leave the star.
The activity of the Sun changes during the 11-year cycle. At the same time, the number of sunspots, radiation levels and the mass of material ejected into space change. And these changes affect the properties of the solar wind - its magnetic field, speed, temperature and density. Therefore, the solar wind can have different characteristics. They depend on where exactly its source was on the Sun. And they also depend on how fast this area rotated.
The speed of the solar wind is higher than the speed of movement of the substance of the coronal holes. And reaches 800 kilometers per second. These holes appear at the poles of the Sun and in its low latitudes. They acquire the largest dimensions during those periods when activity on the Sun is minimal. Temperatures of matter carried by the solar wind can reach 800,000 C.
In the coronal streamer belt located around the equator, the solar wind moves more slowly - about 300 km. per second. It has been established that the temperature of matter moving in the slow solar wind reaches 1.6 million C.
The sun and its atmosphere are made up of plasma and a mixture of positively and negatively charged particles. They have extremely high temperatures. Therefore, matter is constantly leaving the Sun, carried away by the solar wind.
Earth impact
When the solar wind leaves the Sun, it carries charged particles and magnetic fields. Radiated in all directions, particles of the solar wind constantly affect our planet. This process produces interesting effects.
If the material carried by the solar wind reaches the surface of the planet, it will cause serious damage to any form of life that exists on. Therefore, the Earth's magnetic field serves as a shield, redirecting the paths of solar particles around the planet. Charged particles seem to "flow" outside of it. The impact of the solar wind changes the Earth's magnetic field in such a way that it is deformed and stretched on the night side of our planet.
Sometimes the Sun ejects large volumes of plasma, known as coronal mass ejections (CMEs), or solar storms. This most often occurs during the active period of the solar cycle, known as solar maximum. CMEs have a stronger effect than the standard solar wind.
Some bodies of the solar system, like the Earth, are shielded by a magnetic field. But many of them do not have such protection. The satellite of our Earth has no protection for its surface. Therefore, it experiences the maximum effect of the solar wind. Mercury, the planet closest to the Sun, has a magnetic field. It protects the planet from the usual standard wind, however it is not able to withstand more powerful flares such as CME.
When high- and low-speed solar wind currents interact with each other, they create dense regions known as rotating interaction regions (CIRs). It is these areas that cause geomagnetic storms when they collide with the earth's atmosphere.
sunny wind and the charged particles it carries can affect Earth's satellites and Global Positioning Systems (GPS). Powerful bursts can damage satellites or cause position errors when using GPS signals of tens of meters.
The solar wind reaches all the planets in . The NASA New Horizons mission discovered it while traveling between and.
Studying the solar wind
Scientists have known about the existence of the solar wind since the 1950s. But despite its massive impact on Earth and astronauts, scientists still don't know many of its characteristics. Several space missions in recent decades have attempted to explain this mystery.
Launched into space on October 6, 1990, the NASA Ulysses mission studied the Sun at different latitudes. She measured various properties solar wind for more than ten years.
The Advanced Composition Explorer () mission had an orbit associated with one of the special points located between the Earth and the Sun. It is known as the Lagrange point. In this region, the gravitational forces from the Sun and the Earth have the same value. And this allows the satellite to have a stable orbit. Started in 1997, the ACE experiment studies the solar wind and provides real-time measurements of a constant stream of particles.
NASA's STEREO-A and STEREO-B spacecraft are studying the edges of the Sun from different directions to see how the solar wind is born. According to NASA, STEREO has provided "a unique and revolutionary look at the Earth-Sun system."
New missions
NASA plans to launch a new mission to study the Sun. It gives scientists hope to learn even more about the nature of the Sun and the solar wind. NASA's Parker Solar Probe, planned for launch ( successfully launched on 12.08.2018 – Navigator) in the summer of 2018, will work in such a way as to literally “touch the Sun”. After several years of flying in orbit close to our star, the probe will plunge into the corona of the Sun for the first time in history. This will be done in order to get a combination of fantastic images and measurements. The experiment will advance our understanding of the nature of the solar corona, and improve our understanding of the origin and evolution of the solar wind.
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Imagine that you heard the words of the announcer in the weather forecast: “Tomorrow the wind will pick up sharply. As a result, there may be interruptions in the operation of the radio, mobile communications and the Internet. US space mission delayed. Intense auroras are expected in the north of Russia…”.
You will be surprised: what nonsense, what does the wind have to do with it? But the fact is that you missed the beginning of the forecast: “Last night there was a solar flare. A powerful stream of solar wind is moving towards the Earth…”.
Ordinary wind is the movement of air particles (molecules of oxygen, nitrogen and other gases). A stream of particles also rushes from the Sun. It is called the solar wind. If you do not delve into hundreds of cumbersome formulas, calculations and heated scientific disputes, then, in general, the picture appears as follows.
Thermonuclear reactions are going on inside our luminary, heating up this huge ball of gases. The temperature of the outer layer - the solar corona reaches a million degrees. This causes the atoms to move at such speed that when they collide, they smash each other to smithereens. It is known that a heated gas tends to expand and occupy a larger volume. Something similar is happening here. Particles of hydrogen, helium, silicon, sulfur, iron and other substances scatter in all directions.
They are gaining more and more speed and in about six days they reach the near-Earth borders. Even if the sun was calm, the speed of the solar wind reaches here up to 450 kilometers per second. Well, when the solar flare erupts a huge fiery bubble of particles, their speed can reach 1200 kilometers per second! Yes, and refreshing "breeze" can not be called - about 200 thousand degrees.
Can a person feel the solar wind?
Indeed, since the flow of hot particles is constantly rushing, why don't we feel how it "blows" us? Suppose the particles are so small that the skin does not feel their touch. But they are not noticed by terrestrial devices either. Why?
Because the Earth is protected from solar vortices by its magnetic field. The flow of particles flows around it, as it were, and rushes further. It is only on days when solar emissions are particularly strong that our magnetic shield has a hard time. A solar hurricane breaks through it and bursts into the upper atmosphere. Alien particles cause . The magnetic field is sharply deformed, weather forecasters talk about "magnetic storms." 
Because of them, space satellites go out of control. Planes disappear from the radar screens. Radio waves are interfered with and communications are disrupted. On such days, satellite dishes are turned off, flights are canceled, and “communication” with spacecraft is interrupted. In electrical networks, railway rails, pipelines, an electric current is suddenly born. From this, traffic lights switch by themselves, gas pipelines rust, and disconnected electrical appliances burn out. Plus, thousands of people feel discomfort and discomfort.
The cosmic effects of the solar wind can be detected not only during flares on the Sun: it is, albeit weaker, but blows constantly.
It has long been observed that the tail of a comet grows as it approaches the Sun. It causes the frozen gases that form the comet's nucleus to evaporate. And the solar wind carries these gases in the form of a plume, always directed in the opposite direction from the Sun. So the terrestrial wind turns the smoke from the chimney and gives it one form or another.
During years of increased activity, the Earth's exposure to galactic cosmic rays drops sharply. The solar wind is gaining such strength that it simply sweeps them to the outskirts of the planetary system.
There are planets in which the magnetic field is very weak, if not completely absent (for example, on Mars). Here nothing prevents the solar wind from roaming. Scientists believe that it was he who, over hundreds of millions of years, almost "blew out" its atmosphere from Mars. Because of this, the orange planet lost sweat and water and, possibly, living organisms.
Where does the solar wind subside?
Nobody knows the exact answer yet. Particles fly to the vicinity of the Earth, picking up speed. Then it gradually falls, but it seems that the wind reaches the farthest corners of the solar system. Somewhere there it weakens and is decelerated by rarefied interstellar matter.
So far, astronomers cannot say exactly how far this happens. To answer, you need to catch particles, flying farther and farther from the Sun, until they stop coming across. By the way, the limit where this will happen can be considered the boundary of the solar system. 
Traps for the solar wind are equipped with spacecraft that are periodically launched from our planet. In 2016, solar wind streams were captured on video. Who knows if he will not become the same familiar "character" of weather reports as our old friend - the earth's wind?
There is a constant stream of particles ejected from the sun's upper atmosphere. We see evidence of the solar wind around us. Powerful geomagnetic storms can damage satellites and electrical systems on Earth, and cause beautiful auroras. Perhaps the best evidence of it is the long tails of comets as they pass near the sun.
Comet dust particles are deflected by the wind and carried away from the Sun, which is why comet tails always point away from our sun.
Solar wind: origin, characteristics
It comes from the upper layers of the Sun's atmosphere, called the corona. In this region, the temperature is over 1 million Kelvin, and the particles have an energy charge of more than 1 keV. There are actually two kinds of solar wind: slow and fast. This difference can be seen in comets. If you look closely at a picture of a comet, you will see that they often have two tails. One is straight and the other is more curved.
Fast solar wind
It travels at 750 km/s and astronomers believe it originates from coronal holes, regions where magnetic field lines pierce the surface of the Sun.
slow solar wind
It has a speed of about 400 km / s, and comes from the equatorial belt of our star. The radiation reaches the Earth, depending on the speed, from several hours to 2-3 days.
The slow solar wind is wider and denser than the fast one, which creates a large, bright comet tail.
If not for the Earth's magnetic field, it would destroy life on our planet. However, the magnetic field around the planet protects us from radiation. The shape and size of the magnetic field is determined by the strength and speed of the wind.
In the late 1940s, the American astronomer S. Forbush discovered an incomprehensible phenomenon. When measuring the intensity of cosmic rays, Forbush noticed that it decreases significantly with increasing solar activity and drops quite sharply during magnetic storms.
It seemed rather strange. Rather, the opposite could be expected. After all, the Sun itself is a supplier of cosmic rays. Therefore, it would seem that the higher the activity of our daylight, the more particles it should throw into the surrounding space.
It remained to assume that the increase in solar activity affects the earth's magnetic field in such a way that it begins to deflect particles of cosmic rays - to reject them. The path to the Earth is, as it were, blocked.
The explanation seemed logical. But, alas, as it soon became clear, it was clearly insufficient. The calculations made by physicists irrefutably testified that the change physical conditions only in the immediate vicinity of the Earth cannot cause an effect of such magnitude as is observed in reality. Obviously, there must be some other forces that prevent the penetration of cosmic rays into the solar system, and, moreover, such that increase with increasing solar activity.
It was then that the assumption arose that the culprits of the mysterious effect are streams of charged particles escaping from the surface of the Sun and penetrating the space of the solar system. This kind of "solar wind" cleans the interplanetary medium, "sweeping out" particles of cosmic rays from it.
Phenomena observed in comets also spoke in favor of such a hypothesis. As you know, comet tails always point away from the Sun. Initially, this circumstance was associated with the light pressure of the sun's rays. However, in the middle of the current century, it was established that light pressure alone cannot cause all the phenomena that occur in comets. Calculations have shown that for the formation and observed deflection of cometary tails, it is necessary to influence not only photons, but also particles of matter. Incidentally, such particles could excite the ion glow that occurs in cometary tails.
As a matter of fact, the fact that the Sun throws out streams of charged particles - corpuscles, was known even before that. However, it was assumed that such flows are episodic. Astronomers associated their occurrence with the appearance of flares and spots. But comet tails are always directed away from the Sun, and not only during periods of increased solar activity. This means that the corpuscular radiation that fills the space of the solar system must also exist constantly. It intensifies with increasing solar activity, but it always exists.
Thus, the near-solar space is continuously blown by the solar wind. What does this wind consist of and under what conditions does it arise?
Let's get acquainted with the outermost layer of the solar atmosphere - the "crown". This part of the atmosphere of our daylight is unusually rarefied. Even in the immediate vicinity of the Sun, its density is only about one hundred millionth of the density of the earth's atmosphere. This means that every cubic centimeter of circumsolar space contains only a few hundred million corona particles. But the so-called "kinetic temperature" of the corona, determined by the speed of particles, is very high. It reaches a million degrees. Therefore, the coronal gas is completely ionized and is a mixture of protons, ions various elements and free electrons.
Recently, a report appeared that the presence of helium ions was detected in the composition of the solar wind. This circumstance spills a spell on the mechanism by which the ejection of charged
particles from the surface of the sun. If the solar wind consisted only of electrons and protons, then one could still assume that it is formed due to purely thermal processes and is something like steam that forms above the surface of boiling water. However, the nuclei of helium atoms are four times heavier than protons and are therefore unlikely to be ejected by evaporation. Most likely, the formation of the solar wind is associated with the action of magnetic forces. Flying away from the Sun, plasma clouds, as it were, carry away magnetic fields with them. It is these fields that serve as that kind of "cement" that "fastens" together particles with different masses and charges.
Observations and calculations carried out by astronomers have shown that as we move away from the Sun, the density of the corona gradually decreases. But it turns out that in the region of the Earth's orbit it is still noticeably different from zero. In this region of the solar system, there are from a hundred to a thousand coronal particles for every cubic centimeter of space. In other words, our planet is located inside the solar atmosphere and, if you like, we have the right to call ourselves not only the inhabitants of the Earth, but also the inhabitants of the atmosphere of the Sun.
If the corona is more or less stable near the Sun, then as the distance increases, it tends to expand into space. And the farther from the Sun, the higher the rate of this expansion. According to the calculations of the American astronomer E. Parker, already at a distance of 10 million km, coronal particles move at speeds exceeding the speed of sound. And as the further away from the Sun and the weakening of the force of solar attraction, these speeds increase several times more.
Thus, the conclusion suggests itself that the solar corona is the solar wind blowing around the space of our planetary system.
These theoretical conclusions have been fully confirmed by measurements on space rockets and artificial earth satellites. It turned out that the solar wind always exists and “blows” near the Earth at a speed of about 400 km/sec. With increasing solar activity, this speed increases.
How far does the solar wind blow? This question is of considerable interest, however, in order to obtain the corresponding experimental data, it is necessary to carry out sounding by spacecraft of the outer part of the solar system. Until this is done, one has to be content with theoretical considerations.
However, a definite answer cannot be obtained. Depending on the initial assumptions, the calculations lead to different results. In one case, it turns out that the solar wind subsides already in the orbit of Saturn, in the other, that it still exists at a very large distance beyond the orbit of the last planet, Pluto. But these are only theoretically the extreme limits of the possible propagation of the solar wind. Only observations can indicate the exact boundary.
The most reliable would be, as we have already noted, data from space probes. But in principle, some indirect observations are also possible. In particular, it was noted that after each successive decline in solar activity, the corresponding increase in the intensity of high-energy cosmic rays, i.e., rays entering the solar system from outside, occurs with a delay of about six months. Apparently, this is just the period that is necessary for the next change in the power of the solar wind to reach the limit of its propagation. Since the average propagation speed of the solar wind is about 2.5 astronomical units (1 astronomical unit = 150 million km - the average distance of the Earth from the Sun) per day, this gives a distance of about 40-45 astronomical units. In other words, the solar wind dries up somewhere around Pluto's orbit.