The reason for the appearance of solar wind is. What is the solar wind? The collapse of the idea of a static solar corona
sunny wind
- a continuous stream of plasma of solar origin, spreading approximately radially from the Sun and filling solar system to heliocentric distances ~100 AU S.v. is formed during gas-dynamic. expansion into interplanetary space. At high temperatures, which exist in solar corona(K), the pressure of the overlying layers cannot balance the gas pressure of the corona matter, and the corona expands.The first evidence of the existence of a constant flow of plasma from the Sun was obtained by L. Biermann (Germany) in the 1950s. on the analysis of forces acting on the plasma tails of comets. In 1957, Yu. Parker (USA), analyzing the equilibrium conditions of the corona matter, showed that the corona cannot be in hydrostatic conditions. equilibrium, as previously assumed, should expand, and this expansion, under the existing boundary conditions, should lead to the acceleration of coronal matter to supersonic speeds.
Average characteristics of S.v. are given in table. 1. For the first time, a plasma flow of solar origin was recorded on the second Soviet spacecraft. rocket "Luna-2" in 1959. The existence of a constant outflow of plasma from the Sun was proven as a result of many months of measurements in America. AMS Mariner 2 in 1962
Table 1. Average characteristics of the solar wind in Earth orbit
| Speed | 400 km/s |
| Proton Density | 6 cm -3 |
| Proton temperature | TO |
| Electron temperature | TO |
| Tension magnetic field | E |
| Proton flux density | cm -2 s -1 |
| Kinetic energy flux density | 0.3 ergsm -2 s -1 |
Streams N.v. can be divided into two classes: slow - with a speed of km/s and fast - with a speed of 600-700 km/s. Fast flows come from those regions of the corona where the magnetic field is close to radial. Some of these areas are . Slow flows N.W. are apparently associated with the areas of the crown where there is meaning. tangential component mag. fields.
In addition to the main components of S.v. - protons and electrons; - particles, highly ionized ions of oxygen, silicon, sulfur, and iron were also found in its composition (Fig. 1). When analyzing gases trapped in foils exposed on the Moon, Ne and Ar atoms were found. Average chem. composition of S.v. is given in table. 2.Table 2. Relative chemical composition solar wind
| Element | Relative content |
| H | 0,96 |
| 3 He | |
| 4 He | 0,04 |
| O | |
| Ne | |
| Si | |
| Ar | |
| Fe |
Ionization state of matter S.v. corresponds to the level in the corona where the recombination time becomes small compared to the expansion time, i.e. on distance . Ionization measurements ion temperatures S.v. make it possible to determine the electron temperature of the solar corona.
S.v. carries the coronal magnetic field with it into the interplanetary medium. field. The field lines of this field frozen into the plasma form an interplanetary magnetic field. field (MMP). Although the IMF intensity is low and its energy density is approx. 1% of kinetic energy of solar energy, it plays a large role in the thermodynamics of solar energy. and in the dynamics of interactions between S.v. with the bodies of the Solar System and the streams of the North. between themselves. Combination of expansion S.v. with the rotation of the Sun leads to the fact that the mag. power lyoniums frozen in the S.V. have a shape close to Archimedes’ spirals (Fig. 2). Radial and azimuthal component of mag. fields near the ecliptic plane change with distance:,
Where R- heliocentric distance, - angular velocity rotation of the sun, u R- radial velocity component S.v., index “0” corresponds to the initial level. At the distance of the Earth's orbit, the angle between the magnetic directions. fields and direction to the Sun, on large heliocentric. IMF distances are almost perpendicular to the direction to the Sun.
S.v., arising over regions of the Sun with different magnetic orientations. fields, forms flows in differently oriented permafrost - the so-called. interplanetary magnetic field.
In N.v. observed Various types waves: Langmuir, whistlers, ion-sonic, magnetosonic, etc. (see). Some waves are generated on the Sun, some are excited in the interplanetary medium. The generation of waves smoothes out deviations of the particle distribution function from the Maxwellian one and leads to the fact that the S.V. behaves like a continuous medium. Alfvén-type waves play a large role in the acceleration of small components of the S.V. and in the formation of the proton distribution function. In N.v. Contact and rotational discontinuities, characteristic of magnetized plasma, are also observed.
Stream N.w. yavl. supersonic in relation to the speed of those types of waves that provide effective transfer of energy into the S.V. (Alfvén, sound and magnetosonic waves), Alfvén and sound Mach numbers S.v. in Earth orbit. When trimming the S.V. obstacles that can effectively deflect S.v. (magnetic fields of Mercury, Earth, Jupiter, Staurn or the conducting ionospheres of Venus and, apparently, Mars), a bow shock wave is formed. S.v. slows down and heats up at the front of the shock wave, which allows it to flow around the obstacle. At the same time, in N.v. a cavity is formed - the magnetosphere (either its own or induced), the shape and size of the structure is determined by the balance of magnetic pressure. fields of the planet and the pressure of the flowing plasma flow (see). The layer of heated plasma between the shock wave and the streamlined obstacle is called. transition region. The temperatures of ions at the front of the shock wave can increase by 10-20 times, electrons - by 1.5-2 times. Shock wave phenomenon. , the thermalization of the flow is ensured by collective plasma processes. The thickness of the shock wave front is ~100 km and is determined by the growth rate (magnetosonic and/or lower hybrid) during the interaction of the oncoming flow and part of the ion flow reflected from the front. In case of interaction between S.v. with a non-conducting body (the Moon), a shock wave does not arise: the plasma flow is absorbed by the surface, and behind the body a SW is formed which is gradually filled with plasma. cavity.The stationary process of corona plasma outflow is superimposed by non-stationary processes associated with. During strong solar flares, matter is ejected from the lower regions of the corona into the interplanetary medium. In this case, a shock wave is also formed (Fig. 3), the edges gradually slow down when moving through the plasma of the SW. The arrival of a shock wave to the Earth leads to compression of the magnetosphere, after which the development of magnetism usually begins. storms
The equation describing the expansion of the solar corona can be obtained from the system of conservation equations for mass and angular momentum. The solutions to this equation, which describe the different nature of the change in speed with distance, are shown in Fig. 4. Solutions 1 and 2 correspond to low velocities at the base of the crown. The choice between these two solutions is determined by the conditions at infinity. Solution 1 corresponds to low rates of expansion of the corona (“solar breeze”, according to J. Chamberlain, USA) and gives large pressure values at infinity, i.e. encounters the same difficulties as the static model. crowns Solution 2 corresponds to the transition of the expansion rate through the speed of sound ( v K) on a certain rum critical. distance R K and subsequent expansion at supersonic speed. This solution gives a vanishingly small value of pressure at infinity, which makes it possible to reconcile it with the low pressure of the interstellar medium. Parker called this type of current the solar wind. Critical the point is above the surface of the Sun if the temperature of the corona is less than a certain critical value. values , where m- proton mass, - adiabatic index. In Fig. Figure 5 shows the change in expansion rate from heliocentric. distance depending on isothermal temperature. isotropic corona. Subsequent models of S.v. take into account variations in the coronal temperature with distance, the two-liquid nature of the medium (electron and proton gases), thermal conductivity, viscosity, and the nonspherical nature of the expansion. Approach to substance S.v. how to a continuous medium is justified by the presence of the IMF and the collective nature of the interaction of the SW plasma, caused by various types of instabilities. S.v. provides the basic outflow of thermal energy from the corona, because heat transfer to the chromosphere, electromagnet. radiation from highly ionized corona matter and electronic thermal conductivity of solar energy. insufficient to establish thermal balance of the crown. Electronic thermal conductivity ensures a slow decrease in the ambient temperature. with distance. S.v. does not play any noticeable role in the energy of the Sun as a whole, because the energy flux carried away by it is ~ 10 -8Figure 1. Helisphere
Figure 2. Solar flare.
sunny wind- a continuous stream of plasma of solar origin, spreading approximately radially from the Sun and filling the Solar System to heliocentric distances of the order of 100 AU. The solar energy is formed during the gas-dynamic expansion of the solar corona into interplanetary space.
Average characteristics of the Solar wind in Earth's orbit: speed 400 km/s, proton density - 6 to 1, proton temperature 50,000 K, electron temperature 150,000 K, magnetic field strength 5 oersted. Solar wind streams can be divided into two classes: slow - with a speed of about 300 km/s and fast - with a speed of 600-700 km/s. The solar wind arising over regions of the Sun with different orientations of the magnetic field forms streams with differently oriented interplanetary magnetic fields - the so-called sector structure of the interplanetary magnetic field.
Interplanetary sector structure is the division of the observed large-scale structure of the Solar wind into an even number of sectors with different directions of the radial component of the interplanetary magnetic field.
The characteristics of the Solar wind (speed, temperature, particle concentration, etc.) also, on average, naturally change in the cross section of each sector, which is associated with the existence of a fast flow of Solar wind inside the sector. The boundaries of the sectors are usually located within the slow flow of the Solar wind. Most often, two or four sectors are observed, rotating with the Sun. This structure, formed when the solar wind stretches the large-scale coronal magnetic field, can be observed over several solar revolutions. The sector structure is a consequence of the existence of a current sheet in the interplanetary medium, which rotates along with the Sun. The current sheet creates a jump in the magnetic field: above the layer, the radial component of the interplanetary magnetic field has one sign, below it - another. The current sheet is located approximately in the plane of the solar equator and has a folded structure. The rotation of the Sun leads to the twisting of the folds of the current layer in a spiral (the so-called “ballerina effect”). Being near the ecliptic plane, the observer finds himself either above or below the current sheet, due to which he finds himself in sectors with different signs of the radial component of the interplanetary magnetic field.
When the Solar wind flows around obstacles that can effectively deflect the Solar wind (magnetic fields of Mercury, Earth, Jupiter, Saturn or the conducting ionospheres of Venus and, apparently, Mars), a bow shock wave is formed. The solar wind slows down and heats up at the front of the shock wave, which allows it to flow around the obstacle. At the same time, a cavity is formed in the Solar wind - the magnetosphere, the shape and size of which is determined by the balance of the pressure of the planet’s magnetic field and the pressure of the flowing plasma flow. The thickness of the shock wave front is about 100 km. In the case of interaction of the Solar wind with a non-conducting body (the Moon), a shock wave does not arise: the plasma flow is absorbed by the surface, and behind the body a cavity is formed that is gradually filled with solar wind plasma.
The stationary process of coronal plasma outflow is superimposed by non-stationary processes associated with solar flares. During strong solar flares, matter is ejected from the lower regions of the corona into the interplanetary medium. This also produces a shock wave, which gradually slows down as it moves through the solar wind plasma.
The arrival of a shock wave to the Earth leads to compression of the magnetosphere, after which the development of a magnetic storm usually begins.
The solar wind extends to a distance of about 100 AU, where the pressure of the interstellar medium balances the dynamic pressure of the solar wind. The cavity swept by the Solar wind in the interstellar medium forms the heliosphere. The solar wind, together with the magnetic field frozen into it, prevents the penetration of low-energy galactic cosmic rays into the Solar System and leads to variations in high-energy cosmic rays.
A phenomenon similar to the Solar wind has also been discovered in some types of other stars (stellar wind).
Flow of solar energy powered by thermonuclear reaction at its center, fortunately, is exceptionally stable, unlike most other stars. Most of it is eventually emitted by the thin surface layer of the Sun - the photosphere - in the form of electromagnetic waves in the visible and infrared range. Solar constant (flux amount solar energy in Earth orbit) is equal to 1370 W/. One can imagine that for every square meter The surface of the Earth accounts for the power of one electric kettle. Above the photosphere is the corona of the Sun - a zone visible from Earth only during solar eclipses and filled with rarefied and hot plasma with a temperature of millions of degrees.
This is the most unstable shell of the Sun, in which the main manifestations arise solar activity, affecting the Earth. The shaggy appearance of the Sun's corona demonstrates the structure of its magnetic field - luminous clumps of plasma stretched along the lines of force. Hot plasma flowing from the corona forms the solar wind - a flow of ions (consisting of 96% hydrogen nuclei - protons and 4% helium nuclei - alpha particles) and electrons, accelerating into interplanetary space at a speed of 400-800 km/s .
The solar wind stretches and carries away the solar magnetic field.
This happens because the energy of the directed motion of the plasma in the outer corona is greater than the energy of the magnetic field, and the freezing-in principle drags the field behind the plasma. The combination of such a radial outflow with the rotation of the Sun (and the magnetic field is “attached” to its surface) leads to the formation of a spiral structure of the interplanetary magnetic field - the so-called Parker spiral.
The solar wind and magnetic field fill the entire solar system, and thus the Earth and all other planets are actually located in the corona of the Sun, experiencing influences not only electromagnetic radiation, but also the solar wind and the solar magnetic field.
During the period of minimum activity, the configuration of the solar magnetic field is close to dipole and similar to the shape of the Earth's magnetic field. As activity approaches its maximum, the structure of the magnetic field, for reasons that are not entirely clear, becomes more complex. One of the most beautiful hypotheses says that as the Sun rotates, the magnetic field seems to wrap around it, gradually plunging under the photosphere. Over time, during just the solar cycle, the magnetic flux accumulated under the surface becomes so large that the bundles of field lines begin to be pushed out.
The exit points of the field lines form spots on the photosphere and magnetic loops in the corona, visible as areas of increased plasma glow in X-ray images of the Sun. The magnitude of the field inside sunspots reaches 0.01 tesla, a hundred times greater than the field of the quiet Sun.
Intuitively, the energy of a magnetic field can be related to the length and number of field lines: the higher the energy, the more of them. When approaching solar maximum, the enormous energy accumulated in the field begins to be periodically released explosively, spent on accelerating and heating particles of the solar corona.
Sharp intense bursts of short-wave electromagnetic radiation from the Sun that accompany this process are called solar flares. On the Earth's surface, flares are recorded in the visible range as small increases in the brightness of individual areas of the solar surface.
However, already the first measurements carried out on board spacecraft, showed that the most noticeable effect of flares is a significant (up to hundreds of times) increase in the flux of solar X-rays and energetic charged particles - solar cosmic rays.
During some flares, significant amounts of plasma and magnetic field are also released into the solar wind - the so-called magnetic clouds, which begin to rapidly expand into interplanetary space, maintaining the shape of a magnetic loop with ends resting on the Sun.
The plasma density and the magnitude of the magnetic field inside the cloud are tens of times higher than the typical quiet time values of these parameters in the solar wind.
Although up to 1025 joules of energy can be released during a major flare, the overall increase in energy flux into solar maximum is small, amounting to only 0.1-0.2%.
There is a constant stream of particles ejected from upper layers atmosphere of the Sun. We see evidence of the solar wind all around us. Powerful geomagnetic storms can damage satellites and electrical systems on Earth, and cause beautiful auroras. Perhaps the best evidence of this is the long tails of comets when they pass close to the Sun.
Dust particles from a comet are deflected by the wind and carried away from the Sun, which is why the tails of comets are always directed away from our star.
Solar wind: origin, characteristics
It comes from the Sun's upper atmosphere, called the corona. In this region, the temperature is more than 1 million Kelvin, and the particles have an energy charge of more than 1 keV. There are actually two types of solar wind: slow and fast. This difference can be seen in comets. If you look at the image of a comet closely, you will see that they often have two tails. One of them is straight and the other is more curved.
Fast solar wind
It is moving at a speed of 750 km/s, and astronomers believe it originates from coronal holes - regions where magnetic field lines make their way to 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 solar wind, which creates the comet's large, bright tail.
If not for the Earth's magnetic field, it would have destroyed 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.
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 sun's activity varies over an 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 located 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 material 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 become largest in size during periods when activity on the Sun is minimal. Temperatures of material 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 composed of plasma and a mixture of positively and negatively charged particles. They have extremely high temperatures. Therefore, matter constantly leaves the Sun, carried away by the solar wind.
Impact on Earth
When the solar wind leaves the Sun, it carries charged particles and magnetic fields. Solar wind particles emitted in all directions constantly impact our planet. This process produces interesting effects.
If material carried by the solar wind reaches the planet's surface, it will cause severe damage to any form of life that exists on the planet. Therefore, the Earth's magnetic field serves as a shield, redirecting the trajectories of solar particles around the planet. Charged particles seem to “flow” outside of it. The influence 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 in the solar system, like the Earth, are shielded by a magnetic field. But many of them do not have such protection. Our Earth's satellite has no protection for its surface. Therefore, it experiences maximum exposure to solar wind. Mercury, the closest planet to the Sun, has a magnetic field. It protects the planet from normal standard wind, but it is not able to withstand more powerful flashes, such as CME.
When high- and low-speed solar wind streams interact with each other, they create dense regions known as rotating interacting regions (CIRs). It is these areas that cause geomagnetic storms when they collide with the earth's atmosphere.
The solar wind and the charged particles it carries can influence Earth satellites and Global Positioning Systems (GPS). Powerful bursts can damage satellites or cause position errors when using GPS signals tens of meters away.
The solar wind reaches all planets in . NASA's New Horizons mission discovered it while traveling between and.
Studying the solar wind
Scientists have known about the existence of solar wind since the 1950s. But despite its serious impact on Earth and astronauts, scientists still don't know many of its characteristics. Some space missions, committed in recent decades, have tried to explain this mystery.
Launched into space on October 6, 1990, NASA's Ulysses mission studied the Sun at different latitudes. She measured various properties of the solar wind for more than ten years.
The Advanced Composition Explorer () mission had an orbit associated with one of singular points located between the Earth and the Sun. It is known as the Lagrange point. In this area gravitational forces from the Sun and the Earth have the same meaning. And this allows the satellite to have a stable orbit. Launched in 1997, the ACE experiment studies the solar wind and provides real-time measurements of the constant flow of particles.
NASA's STEREO-A and STEREO-B spacecraft study the edges of the Sun from different angles to see how the solar wind is generated. According to NASA, STEREO introduced a "unique and revolutionary view to the Earth-Sun system."
New missions
NASA is planning to launch a new mission to study the Sun. It gives scientists hope to learn even more about the nature of the Sun and solar wind. NASA Parker solar probe planned for launch ( successfully launched 08/12/2018 – Navigator) in the summer of 2018, will work in such a way as to literally “touch the Sun”. After several years of flight in orbit close to our star, the probe will plunge into the solar corona for the first time in history. This will be done in order to obtain a combination of fantastic images and measurements. The experiment will advance our understanding of the nature of the solar corona, and improve understanding of the origin and evolution of the solar wind.
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SUNNY WIND- a continuous stream of plasma of solar origin, spreading approximately radially from the Sun and filling the Solar System to the heliocentric. distances R ~ 100 a. e. S. v. is formed during gas-dynamic. expansion of the solar corona (see Sun)into interplanetary space. At high temperatures, which exist in the solar corona (1.5 * 10 9 K), the pressure of the overlying layers cannot balance the gas pressure of the corona matter, and the corona expands.
The first evidence of the existence of post. plasma flows from the Sun were obtained by L. Biermann in the 1950s. on the analysis of forces acting on the plasma tails of comets. In 1957, Yu. Parker (E. Parker), analyzing the equilibrium conditions of the corona matter, showed that the corona cannot be in hydrostatic conditions. equilibrium, as was previously assumed, but should expand, and this expansion, under the existing boundary conditions, should lead to the acceleration of coronal matter to supersonic speeds (see below). For the first time, a plasma flow of solar origin was recorded in the Soviet spacecraft. spacecraft "Luna-2" in 1959. Existence post. the outflow of plasma from the Sun was proven as a result of many months of measurements in America. space the Mariner 2 apparatus in 1962.
Wed. characteristics of S. v. are given in table. 1. S. flows. can be divided into two classes: slow - with a speed of 300 km/s and fast - with a speed of 600-700 km/s. Fast flows come from regions of the solar corona, where the structure of the magnetic field. fields are close to radial. Some of these areas are coronal holes. Slow flows of the North century. are apparently connected with the regions of the crown, in which there is, therefore, a tangential magnetic component. fields.
Table 1.- Average characteristics of the solar wind in Earth orbit
|
Speed |
|
|
Proton concentration |
|
|
Proton temperature |
|
|
Electron temperature |
|
|
Magnetic field strength |
|
|
Python flux density.... |
2.4*10 8 cm -2 *c -1 |
|
Kinetic energy flux density |
0.3 erg*cm -2 *s -1 |
Table 2.- Relative chemical composition of the solar wind
|
Relative content |
|
|
Relative content |
|
In addition to the main components of solar water are protons and electrons; highly ionized particles are also found in its composition. ions of oxygen, silicon, sulfur, iron (Fig. 1). When analyzing gases trapped in foils exposed on the Moon, Ne and Ar atoms were found. Wed. relative chem. composition of S. v. is given in table. 2. Ionization. state of matter S. v. corresponds to the level in the corona where the recombination time is short compared to the expansion time 
Ionization measurements temperature of ions S. v. make it possible to determine the electron temperature of the solar corona.
In the N. century. differences are observed. types of waves: Langmuir, whistlers, ion-sonic, magnetosonic, Alfven, etc. (see. Waves in plasma Some of the Alfven type waves are generated on the Sun, and some are excited in the interplanetary medium. The generation of waves smoothes out deviations of the particle distribution function from the Maxwellian one and, in combination with the influence of magnetism. fields on the plasma leads to the fact that S. v. behaves like a continuous medium. Alfvén-type waves play a large role in the acceleration of small components of the solar wave. and in the formation of the proton distribution function. In the N. century. contact and rotational discontinuities characteristic of magnetized plasma are also observed. 
Rice. 1. Mass spectrum of the solar wind. Along the horizontal axis is the ratio of the mass of a particle to its charge, along the vertical axis is the number of particles registered in the energy window of the device in 10 s. Numbers with a “+” sign indicate the charge of the ion.
Stream N. in. is supersonic in relation to the speeds of those types of waves that provide eff. transfer of energy to the S. century. (Alfven, sound and magnetosonic waves). Alfven and sound Mach number C.V. in Earth's orbit 7. When flowing around the northeast. obstacles capable of effectively deflecting it (magnetic fields of Mercury, Earth, Jupiter, Saturn or the conducting ionospheres of Venus and, apparently, Mars), a departing bow shock wave is formed. S.v. slows down and heats up at the front of the shock wave, which allows it to flow around the obstacle. At the same time, in the North century. a cavity is formed - the magnetosphere (either its own or induced), the shape and dimensions of the shape are determined by the balance of magnetic pressure. fields of the planet and the pressure of the flowing plasma flow (see. Magnetosphere of the Earth, Magnetospheres of the planets). In case of interaction with S. v. with a non-conducting body (for example, the Moon), a shock wave does not occur. The plasma flow is absorbed by the surface, and a cavity is formed behind the body, which is gradually filled with plasma from the plasma.
The stationary process of corona plasma outflow is superimposed by non-stationary processes associated with solar flares. During strong flares, substances are released from below. corona regions into the interplanetary medium. In this case, a shock wave is also formed (Fig. 2), which gradually slows down, spreading in the plasma of the solar system. The arrival of a shock wave to the Earth causes compression of the magnetosphere, after which the development of magnetism usually begins. storms (see Magnetic variations).
Rice. 2. Propagation of an interplanetary shock wave and ejection from a solar flare. The arrows show the direction of motion of the solar wind plasma, the lines without a caption are the magnetic field lines.
Rice. 3. Types of solutions to the corona expansion equation. Speed and distance are normalized to the critical speed vk and the critical distance Rk. Solution 2 corresponds to the solar wind.
The expansion of the solar corona is described by a system of equations of conservation of mass, angular momentum and energy equations. Solutions that meet various the nature of the change in speed with distance are shown in Fig. 3. Solutions 1 and 2 correspond to low velocities at the base of the crown. The choice between these two solutions is determined by the conditions at infinity. Solution 1 corresponds to low rates of expansion of the corona and gives large values of pressure at infinity, i.e., it encounters the same difficulties as the static model. crowns Solution 2 corresponds to the transition of the expansion rate through the speed of sound values ( v to) on some critical. distance R to and subsequent expansion at supersonic speed. This solution gives a vanishingly small value of pressure at infinity, which makes it possible to reconcile it with the low pressure of the interstellar medium. This type of flow was called S. by Yu. Parker. Critical the point is above the surface of the Sun if the temperature of the corona is less than a certain critical value. values 
, where m is the proton mass, is the adiabatic exponent, and is the mass of the Sun. In Fig. Figure 4 shows the change in expansion rate from heliocentric. distance depending on isothermal temperature. isotropic corona. Subsequent models of S. century. take into account variations in coronal temperature with distance, two-liquid nature of the medium (electron and proton gases), thermal conductivity, viscosity, non-spherical. nature of expansion. 
Rice. 4. Solar wind speed profiles for the isothermal corona model at different values of coronal temperature.
S.v. provides the basic outflow of thermal energy from the corona, since heat transfer to the chromosphere, el-magn. Corona radiation and electron thermal conductivity are insufficient to establish the thermal balance of the corona. Electronic thermal conductivity ensures a slow decrease in temperature. with distance. S.v. does not play any noticeable role in the energy of the Sun as a whole, since the energy flow carried away by it is ~10 -7 luminosity Sun.
S.v. carries the coronal magnetic field with it into the interplanetary medium. field. The field lines of this field frozen into the plasma form an interplanetary magnetic field. field (MMP). Although the IMF intensity is low and its energy density is approx. 1% of kinetic density energy of solar energy, it plays a large role in the thermodynamics of solar energy. and in the dynamics of interactions of S. v. with the bodies of the solar system, as well as the streams of the north. between themselves. Combination of expansion of the S. century. with the rotation of the Sun leads to the fact that the mag. the lines of force frozen into the north century have a shape close to the Archimedes spiral (Fig. 5). Radial B R and azimuthal magnetic components. fields change differently with distance near the ecliptic plane: 
where is ang. speed of rotation of the Sun, And- radial component of the velocity of the central air, index 0 corresponds to the initial level. At the distance of the Earth's orbit, the angle between the direction of the magnetic. fields and R about 45°. At large L magnetic. the field is almost perpendicular to R. 
Rice. 5. Shape of the interplanetary magnetic field line. - angular velocity of rotation of the Sun, and - radial component of plasma velocity, R - heliocentric distance.
S. v., arising over regions of the Sun with different. magnetic orientation fields, forms flows with differently oriented permafrost. Separation of the observed large-scale structure of the solar system. for an even number of sectors with different the direction of the radial component of the IMF is called. interplanetary sector structure. Characteristics of S. v. (speed, temp-pa, particle concentration, etc.) also on Wed. change naturally in the cross section of each sector, which is associated with the existence of a fast flow of solar water inside the sector. The boundaries of the sectors are usually located within the slow flow of the north. Most often, 2 or 4 sectors are observed, rotating with the Sun. This structure, formed when the S. is pulled out. large-scale mag. corona fields, can be observed for several. revolutions of the Sun. The sector structure of the IMF is a consequence of the existence of a current layer (CS) in the interplanetary medium, which rotates together with the Sun. TS creates a magnetic surge. fields - the radial components of the IMF have different signs on different sides of the vehicle. This TS, predicted by H. Alfven, passes through those parts of the solar corona that are associated with active regions on the Sun, and separates these regions from the various regions. signs of the radial component of the solar magnet. fields. The TS is located approximately in the plane of the solar equator and has a folded structure. The rotation of the Sun leads to the twisting of the folds of the TC into a spiral (Fig. 6). Being near the ecliptic plane, the observer finds himself either above or below the TS, due to which he ends up in sectors with different signs of the IMF radial component.
Near the Sun in the north. There are longitudinal and latitudinal velocity gradients caused by the difference in the velocities of fast and slow flows. As you move away from the Sun and the boundary between the streams in the north becomes steeper. radial velocity gradients arise, which lead to the formation collisionless shock waves(Fig. 7). First, a shock wave is formed, propagating forward from the boundary of the sectors (forward shock wave), and then a reverse shock wave is formed, propagating towards the Sun. 
Rice. 6. Shape of the heliospheric current layer. Its intersection with the ecliptic plane (inclined to the solar equator at an angle of ~ 7°) gives the observed sector structure of the interplanetary magnetic field.
Rice. 7. Structure of the interplanetary magnetic field sector. Short arrows show the direction of solar wind plasma flow, lines with arrows - magnetic field lines, dash-dotted lines - sector boundaries (intersection of the drawing plane with the current layer).
Since the speed of the shock wave is less than the speed of the solar energy, the plasma entrains the reverse shock wave in the direction away from the Sun. Shock waves near the sector boundaries are formed at distances of ~1 AU. e. and can be traced to distances of several. A. e. These shock waves, as well as interplanetary shock waves from solar flares and circumplanetary shock waves, accelerate particles and are, therefore, a source of energetic particles.
S.v. extends to distances of ~100 AU. e., where the pressure of the interstellar medium balances the dynamic. blood pressure The cavity swept by the S. v. in the interstellar medium, forms the heliosphere (see. Interplanetary environment). Expanding S. v. along with the magnet frozen into it. field prevents the penetration of galactic particles into the Solar System. space rays of low energies and leads to variations in cosmic. high energy rays. A phenomenon similar to the S.V. has also been discovered in certain other stars (see Stellar wind).
Lit.: Parker E. N., Dynamic processes in the interplanetary medium, trans. from English, M., 1965; Brandt J., Solar Wind, trans. from English, M., 1973; Hundhausen A., Corona Expansion and the Solar Wind, trans. from English, M., 1976. O. L. Weisberg.