Can reach values \u200b\u200bup to 1.1 million degrees Celsius. Therefore, having such a temperature, the particles move very quickly. The gravity of the Sun can not hold them - and they leave the star.

The activity of the Sun is changing during the 11-year cycle. At the same time, the amount of solar spots, radiation levels and mass of the material thrown into space change. And these changes affect the properties of the solar wind - its magnetic field, speed, temperature and density. Therefore, the sunny wind can have different characteristics. They depend on where its source in the sun specifically was. And they also depend on how quickly this area rotated.

The speed of the solar wind is higher than the speed of the substance of the coronal holes. And reaches 800 kilometers per second. These holes occur on the poles of the Sun and in its low latitudes. They acquire the greatest dimensions in those periods when the activity in the sun is minimal. The temperature of the substance carried by the solar wind can reach 800,000 C.

In the belt of the coronal strife, located around the equator, the sun's wind is moving slower - about 300 km. per second. It has been established that the temperature of the substance moving in slow sunny wind reaches 1.6 million C.

The sun and its atmosphere consist of plasma and mixtures of positively and negatively charged particles. They have extremely high temperatures. Therefore, Matter constantly leaves the sun, carrying the sunshine.

Impact on the Earth

When the sunny wind leaves the sun, it carries charged particles and magnetic fields. Emitted in all directions of the solar wind particles constantly affects our planet. This process causes interesting effects.

If the material carrying 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 magnetic field of the Earth serves as a shield, redirecting the trajectories of solar particles around the planet. Charged particles as it were to "flow" beyond. The impact of the solar wind changes the magnetic field of the Earth in such a way that it is deformed and stretched on the night side of our planet.

Sometimes the sun throws large plasma volumes, known as coronal mass emissions (CME), or solar storms. Most often this occurs during the active period of the solar cycle, known as the solar maximum. CME have a stronger effect than standard sunny 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. Satellite of our Earth - has no protection for its surface. Therefore, the maximum impact of the solar wind is experiencing. Mercury, the next to the sun planet, is a magnetic field. It protects the planet from the usual standard wind, but it is not able to withstand more powerful flashes, such as CME.

When high-speed streams of solar wind interact with each other, they create dense areas known as areas with rotating interaction (CIR). It is these areas that cause geomagnetic storms in a collision with an earthly atmosphere.

Sunny wind and charged particles that he carries can affect Earth satellites and global positioning systems (GPS). Powerful bursts can damage satellites or cause coordinate definition errors when using GPS signals in tens of meters.

Sunny wind reaches all planets in. The Mission of Nasa New Horizons discovered it when he traveled between and.

Study of sunny wind

Scientists are aware of the existence of solar wind since the 1950s. But despite its serious impact on Earth and cosmonauts, scientists still do not know many of its characteristics. Several space missions committed in recent decades have tried to explain this mystery.

Launched into space on October 6, 1990, the Mission of Nasa Ulysses studied the sun on its different latitudes. It measured the various properties of the solar wind for more than ten years.

The ADVANCED COMPOSITION EXPLORER () mission had an orbit associated with one of the special points between the Earth and the Sun. She is known as a point of Lagrange. In this area, 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 sunny wind and provides measurements of the constant flow of particles in real time.

NASA Stereo-A and Stereo-B spacecraft study the edges of the sun from different sides to see how sunny wind is born. According to NASA, Stereo introduced a "unique and revolutionary look at the Land - Sun system."

New missions

NASA plans to launch a new sun studying mission. It gives scientists hope to learn even more about the nature of the sun and the sunshine. Sunny Probe NASA PARKER, planned to launch ( successfully launched 12.08.2018 - Navigator) In the summer of 2018, it will work in such a way as to literally "touch the Sun". A few years later, a flight in orbit close to our star, the probe for the first time in history will plunge into the crown of the Sun. This will be done in order to get a combination of fantastic images and measurements. The experiment will promote our understanding of the nature of the solar crown, and will improve the understanding of the origin and evolution of the solar wind.

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In the late 40s, American astronomer S. Forbush discovered an incomprehensible phenomenon. Measuring the intensity of cosmic rays, the forbust noticed that it decreases significantly with increasing solar activity and falls completely sharply during magnetic storms.

It seemed rather strange. Rather, it was possible to expect the opposite. After all, the sun itself is a supplier of cosmic rays. Therefore, it would seem that the higher the activity of our daylight shine, the more particles it should be thrown 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 the particles of cosmic rays - to discard them. The path to the earth will be locked.

The explanation seemed logical. But, alas, as it turned out soon, it was clearly insufficient. The calculations made by physicists, irrefutably testified that the change in physical conditions only in close proximity to the Earth cannot cause the effect of such a scale, which is actually observed. Obviously, there must be any other forces that prevent the penetration of cosmic rays into the solar system, and moreover, such as increasing with an increase in solar activity.

At that time, it was assumed that the perpetrators of the mysterious effect are the flow of charged particles, escaping from the surface of the Sun and permeating the space of the solar system. This peculiar "sunny wind" and purifies the interplanetary medium, "spilled" from it particles of cosmic rays.

In favor of such a hypothesis, phenomena observed in comets also said. As you know, cometic tails are always directed from the sun. Initially, this circumstance was associated with light pressure of sunlight. However, in the middle of the current century it was found that only the light pressure cannot cause all phenomena occurring in comets. Calculations have shown that for the formation and observed deviation of comettails, it is necessary to effect not only photons, but also particles of the substance. By the way, such particles could excite the glow of ions occurring in knetary tails.

Actually, that the sun throws the flows of charged particles - the corpuscles, it was also known before. However, it was assumed that such streams are episodic. Their emergence of astronomers associated with the advent of outbreaks and spots. But comette tails are directed to the opposite side of the sun, and not only during periods of solar activity. So, the corpuscular radiation, filling the space of the solar system, should exist permanently. It is enhanced with increasing solar activity, but there is always.

Thus, the near-free space is continuously blown by the solar wind. What is this wind and under what conditions does it occur?

We will get acquainted with the most outer layer of the solar atmosphere - "Crown". This part of the atmosphere of our daylight is extremely resolved. Even in the immediate vicinity of the Sun, its density is only about one hundredthillional fraction of the density of the earth's atmosphere. This means that in each cubic centimeter of near-free space, only a few hundred million particles of the crown are contained. But the so-called "kinetic temperature" of the crown, determined by the speed of the particle movement, is very large. It reaches a million degrees. Therefore, the coronal gas is completely ionized and is a mixture of protons, ions of various elements and free electrons.

Recently, a message appeared that the presence of helium ions was found as part of the solar wind. This circumstance sheds the sleepers on the mechanism by which the charged

particles from the surface of the sun. If the solar wind consists only of electrons and protons, then it would be possible to assume that it is formed due to pure thermal processes and is something like a steam generated above the surface of boiling water. However, the kernel of helium atoms are four times heavier than protons and therefore it is unlikely that they can be discharged due to evaporation. Most likely the formation of the solar wind is associated with the action of magnetic forces. Flipped from the sun, plasma clouds as it were to carry with them and magnetic fields. It is these fields that serve the peculiar "cement", which "bonds" together particles with various masses and charges.

Observations and calculations conducted by astronomers showed that as the density of the crown is gradually decreasing. But it turns out that in the region of the Earth's orbit, it is still noticeably different from zero. In this area of \u200b\u200bthe solar system on each cubic centimeter, space falls from one hundred and thousands of coronal particles. In other words, our planet is inside the solar atmosphere and, if you want, we have the right to call ourselves not only by the inhabitants of the Earth, but also inhabitants of the sun atmosphere.

If the crown is more or less stable near the sun, then as the distance increases, it seeks to expand into space. And the farther from the Sun, the higher the speed of this expansion. According to the calculations of American astronomer E. Parker, there are already 10 million km of coronal particles moving at speeds, superior sound speed. And no further removal from the sun and the weakening of the solar force of the solar attraction, these speeds increase several times.

Thus, it suggests that the solar crown is a sunny wind that blows the space of our planetary system.

These theoretical conclusions were fully confirmed by the measurements of the space rockets and artificial satellites of the Earth. It turned out that the sunny wind always exists and near the ground "blows" at a speed of about 400 km / s. With increasing solar activity, this speed increases.

How far blows the sunny wind? This question is considerable interest, but to obtain the appropriate experimental data it is necessary to communicate with spacecraft of the external part of the solar system. It is not done yet, it is necessary to be content with theoretical considerations.

However, the unequivocal answer cannot be obtained. Depending on the source prerequisites, calculations lead to different results. In one case, it turns out that the sunny wind subsides already in the Orbit of Saturn, in another, - that it exists at a very long distance behind the orbit of the last planet of Pluton. But it is only the theoretically extreme limits of the possible propagation of solar wind. Indicate the exact boundary can only observations.

The most reliable would be, as we have already noted, the data of space probes. But in principle, some indirect observations are also possible. In particular, it was observed that after each next decline in solar activity, the corresponding increase in the intensity of high-energy cosmic rays, i.e., the rays coming in the sunny system from the outside occurs with the receipt of about six months. Apparently, this is just that time that is needed that the next change in the power of the solar wind has come to the border of its distribution. Since the average rate of propagation of the solar wind is about 2.5 astronomical unit (1 astronomical unit \u003d 150 million km-average distance of the earth from the Sun) per day, then this gives a distance of about 40-45 astronomical units. In other words, the sunny wind dries out somewhere in the area of \u200b\u200bthe orbit of Pluto.

Concept sunny wind It was introduced into astronomy at the end of the 40s of the 20th of the 20th, when American astronomer C. Forbush, measuring the intensity of cosmic rays, noted that it significantly decreases with increasing solar activity and falls completely sharply during.

It seemed rather strange. Rather, it was possible to expect the opposite. After all, the sun itself is a supplier of cosmic rays. Therefore, it would seem, the higher, the activity of our daylight shine, the greater the particles it should be thrown into the surrounding space.

It remained to assume that the increase in solar activity affects such a way that it begins to deflect the particles of cosmic rays - to discard them.

At that time, it was assumed that the perpetrators of the mysterious effect are the flow of charged particles, escaping from the surface of the Sun and permeating the space of the solar system. This peculiar solar wind and purifies the interplanetary medium, "spilled" from it particles of cosmic rays.

In favor of such a hypothesis, phenomena observed in. As you know, cometic tails are always directed from the sun. Initially, this circumstance was associated with light pressure of sunlight. However, it was found that only the light pressure cannot cause all phenomena occurring in comets. Calculations have shown that for the formation and observed deviation of comettails, it is necessary to effect not only photons, but also particles of the substance.

Actually, that the sun throws the flows of charged particles - the corpuscles, it was also known before. However, it was assumed that such streams are episodic. But comette tails are directed to the opposite side of the sun, and not only during periods of amplification. So, the corpuscular radiation, filling the space of the solar system, should exist permanently. It is enhanced with increasing solar activity, but there is always.

Thus, the sunny wind continuously blows up the near-free space. What is this sunny wind, and under what conditions does it occur?

The most outer layer of the solar atmosphere is "crown". This part, the atmosphere of our daylight is extremely resolved. But the so-called "kinetic temperature" of the crown, determined by the speed of movement of particles, is very large. It reaches a million degrees. Therefore, the coronal gas is completely ionized and is a mixture of protons, ions of various elements and free electrons.

Recently a message appeared that the solar wind has helium ions in its composition. This circumstance sheds the light to the mechanism by which the charged particles are released from the surface of the Sun. If the solar wind consists only of electrons and protons, then it would be possible to assume that it is formed due to pure thermal processes and is something like a steam generated above the surface of boiling water. However, the kernel of helium atoms are four times heavier than protons and therefore it is unlikely that they can be discharged due to evaporation. Most likely, the formation of the solar wind is associated with the action of magnetic forces. Flipped from the sun, plasma clouds as it were to carry with them and magnetic fields. It is these fields that serve as a kind of "cement", which "fastens" together particles with various masses and charges.

Observations and calculations conducted by astronomers showed that as the density of the crown is gradually decreasing. But it turns out that in the region of the Earth's orbit, it is still noticeably different from zero. In other words, our planet is located inside the solar atmosphere.

If the crown is more or less stable near the sun, then as the distance increases, it seeks to expand into space. And the farther from the Sun, the higher the speed of this expansion. According to the calculations of American astronoma, E. Parker, already at a distance of 10 million km. Coronal particles move with speeds, superior speed.

Thus, it suggests that the solar crown is a sunny wind that blows the space of our planetary system.

These theoretical conclusions were fully confirmed by measurements on space missiles and artificial satellites of the Earth. It turned out that the sunny wind always exists and near the ground - "blowing" at a speed of about 400 km / s.

How far blows the sunny wind? In theoretical considerations, in one case, it turns out that the solar wind subsides already in the orbit area, in another, - that it exists at a very long distance behind the orbit of the last planet of Pluto. But it is only the theoretically extreme limits of the possible propagation of solar wind. Indicate the exact boundary can only observations.

V.B. Baranov, Moscow State University. M.V. Lomonosov

The article discusses the problem of supersonic expansion of the solar crown (solar wind). Four main problems are analyzed: 1) the reasons for the expiration of the plasma from the solar crown; 2) whether such an expiration is uniform; 3) Changing the parameters of the solar wind with removal from the Sun and 4) as the solar wind expires to the interstellar medium.

Introduction

Almost 40 years have passed since the American physicist E. Parker theoretically predicted the phenomenon that was called "Sunny Wind" and which after a couple of years was confirmed by experimentally by the group of Soviet scientist K. Gringaus with the help of devices installed on spacecraft "Luna 2 "and" Luna-3 ". The solar wind is a flow of fully ionized hydrogen plasma, that is, gas consisting of electrons and protons of about the same density (the quasi-neutrality condition), which is moving from the sun with a large supersonic speed. In the orbit of the Earth (on one astronomical unit (A.E.) from the Sun) the velocity of this stream is approximately 400-500 km / s, the concentration of protons (or electrons) NE \u003d 10-20 particles in a cubic centimeter, and their temperature TE It is approximately 100,000 K (the temperature of the electrons is slightly higher).

In addition to electrons and protons in the interplanetary space, alpha particles were found (about a few percent), a small amount of heavier particles, as well as a magnetic field, the average value of the induction was in the orbit of the Earth of the order of several gamps (1

A bit of history associated with theoretical prediction of the solar wind

During the non-so long history of theoretical astrophysics, it was believed that all the atmosphere of stars are located in hydrostatic equilibrium, that is, in a state where the strength of the gravitational attraction of the star is balanced by the force associated with the pressure gradient in its atmosphere (with a change in pressure per unit of distance R from the center stars). Mathematically, this equilibrium is expressed as an ordinary differential equation.

where G is the gravitational constant, M * - the mass of the stars, P is the pressure of the atmospheric gas,

where R is a gas constant, the so-called barometric formula is easily obtained, which in a particular case of a constant temperature t will be

In formula (3), the p0 is the pressure at the base of the star atmosphere (at r \u003d r0). From this formula, it can be seen that

Since it was believed that the solar atmosphere, as well as the atmosphere of other stars, is in a state of hydrostatic equilibrium, then its condition was determined by formulas similar to formulas (1), (2), (3). Considering the unusual and to the end, the incomprehensible phenomenon of a sharp increase in temperature is about 10,000 degrees on the surface of the Sun to 1,000,000 degrees in the solar crown, Chapman (see, for example,) developed the theory of static solar crown, which should have been smoothly moved to the interstellar medium surrounding the solar system.

However, in his pioneer work, Parker drew attention to the fact that the pressure on infinity obtained from the type (3) formula for a static solar crown is almost an order of magnitude greater than the pressure value that was estimated for interstellar gas based on observations. To eliminate this discrepancy, Parker suggested that the solar crown is not in a state of static equilibrium, and the interplanetary medium continuously expands into the surrounding sun. At the same time, instead of equilibrium equation (1), he proposed to use the hydrodynamic equation of the movement of the form

where in the coordinate system associated with the Sun, the value of V is the radial speed of the plasma movement. Under

At a given temperature distribution of T, the system of equations (2) and (4) has solutions of the type presented in Fig. 1. In this figure, the speed of the sound is indicated, and R * is the distance from the beginning of the coordinates, on which the gas speed is equal to the sound velocity (V \u003d a). Obviously, only curves 1 and 2 in Fig. 1 have a physical meaning for the problem of gas expiration from the Sun, since the curves 3 and 4 have non-limmic velocity values \u200b\u200bat each point, and the curves 5 and 6 correspond to very high speeds in the solar atmosphere, which is not observed in telescopes. Parker analyzed the conditions under which the solution is carried out in nature, corresponding to the curve 1. It showed that to harmonize the pressure obtained from such a decision, the most realized gas transition case from the dialing flow (with R< r*) к сверхзвуковому (при r > R *), and called such a flow of sunshine. However, this statement was challenged in the work of Chamberlain, which believed the most real solution corresponding to curve 2 describing everywhere dialing "Sunny Breeze". At the same time, the first experiments on spacecraft (see, for example,), discovered supersonic gas flows from the Sun, did not seem, judging by the literature, Chamberrine is quite reliable.

The history of experiments in outer space brilliantly proved the correctness of Parker's ideas about solar wind. Detailed material about the theory of solar wind can be found, for example, in the monograph.

Representations of a homogeneous expiration of the plasma from the solar crown

From the one-dimensional equations of gas dynamics, it is possible to obtain a well-known result: in the absence of massive forces, the spherically symmetric flow of gas from the point source can be everywhere or dialing or supersonic. The presence in the gravitational force equation (4) (the right side) leads to the fact that decisions of the curve type 1 appear in Fig. 1, that is, with the transition through the speed of the sound. We will draw an analogy with the classical flow into the nozzle of the boil, which is the basis of all supersonic jet engines. Schematically, this flow is shown in Fig. 2.

In the tank 1, called the receiver, with a very short speed gas heated to a very high temperature (the internal energy of gas is much more than its kinetic energy of the directional movement). By geometric supply of the channel, the gas is accelerated in the region 2 (dialing flow) until its speed reaches the speed of sound. To further accelerate it, the channel is necessary to expand (region 3 of the supersonic flow). In the entire flow area, the acceleration of gas occurs due to its adiabatic (without heat supply) of cooling (the internal energy of the chaotic movement goes into the energy of the directional movement).

In the problem of the formation of the solar wind, the role of the receiver plays a solar crown, and the role of the walls of the boiler's nozzle is the gravitational solar attraction force. According to Parker's theory, the transition through the speed of sound should occur somewhere at a distance of several solar radius. However, the analysis of the solutions obtained in the theory showed that the temperature of the solar crown is not enough so that its gas can accelerate until supersonic velocities, as is the case in the theory of Laval's nozzle. There must be some additional source of energy. Such a source is currently considered dissipation of wave movements that are always present in the solar wind (sometimes they are called plasma turbulence), superimposed on the average course, and the amount itself is no longer adiabatic. Quantitative analysis of such processes still requires its research.

Interestingly, ground telescopes are found on the surface of the Sun magnetic fields. The average value of their magnetic induction in is estimated in 1 GC, although in separate photospheres, for example, in spots, the magnetic field may be more magnitude. Since the plasma is a good conductor of electricity, it is natural that solar magnetic fields interact with its streams from the Sun. In this case, pure gas-dynamic theory gives an incomplete description of the phenomenon under consideration. The effect of the magnetic field during the flow of solar wind can only be considered within science, which is called magnetic hydrodynamics. What results lead such considerations? According to the pioneer in this direction of work (see also), the magnetic field leads to the appearance of electrical currents J in the plasma of the solar wind, which, in turn, leads to the appearance of the ponderomotor force J x B, which is directed in perpendicular to the radial direction. As a result, the solar wind appears a tangential velocity component. This component is almost two orders of magnitude less than radial, but it plays a significant role in the removal of the moment of the amount of movement. It is assumed that the latter circumstance can play a significant role in the evolution of not only the sun, but also from other stars, which have a "star wind". In particular, it is often attracted to explaining a sharp decrease in the angular speed of stars of late spectral class, a hypothesis about the transmission of the rotational moment of the planets generated around them. The considered mechanism for the loss of angular momentum of the Sun by expiration of plasma opens the ability to revise this hypothesis.

There is a constant flow of particles emitted from the upper layers of the sun atmosphere. We see evidence of the solar wind around us. Powerful geomagnetic storms can damage satellites and electrical systems on Earth, and cause beautiful polar shines. Perhaps the best proof of it is the long tails of comets when they pass near the sun.

Comets dust particles are rejected by the wind and are worn from the sun, which is why comet's tails are always directed from our luminaries.

Sunny Wind: Origin, Characteristics

It comes from the upper layers of the sun atmosphere, called the crown. In this region, the temperature of more than 1 million Kelvinov, and the particles have an energy charge of more than 1 keV. There are actual two types of sunny wind: slow and fast. This difference can be seen in comets. If you look at the comet image carefully, you will see that they often have two tails. One of them is straight, and the other is more curved.

Fast sunny wind

It moves at a speed of 750 km / s, and astronomers believe that it occurs from coronal holes - regions, where the power lines of the magnetic field make their way to the surface of the Sun.

Slow sunny wind

It has a speed of about 400 km / s, and comes from the equatorial belt of our star. Radiation reaches Earth, depending on speed, from several hours, up to 2-3 days.

Slow solar wind is wider and tight than the fast, which creates a big, bright tail of the comet.

If it were not for the magnetic field of the Earth, he 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.