Sunny wind. What is the solar wind and how does it arise? solar wind phenomenon

sunny wind

- a continuous stream of plasma of solar origin, propagating approximately radially from the Sun and filling the solar system with itself to the heliocentric. distances ~100 AU S.v. formed during gas-dynamic expansion into interplanetary space. At high temperatures, which exist in the 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 plasma flow from the Sun was obtained by L. Birman (Germany) in the 1950s. on the analysis of the forces acting on the plasma tails of comets. In 1957, J. Parker (USA), analyzing the equilibrium conditions for the corona matter, showed that the corona cannot be under hydrostatic conditions. equilibrium, as was previously assumed, but should expand, and this expansion, under the existing boundary conditions, should lead to acceleration of the coronal matter to supersonic velocities.

Average characteristics S.v. are given in table. 1. For the first time, a plasma flux of solar origin was registered at the second Soviet spacecraft. rocket "Luna-2" in 1959. The existence of a constant outflow of plasma from the Sun was proved as a result of many months of measurements on the Amer. AMS "Mariner-2" in 1962

Table 1. Average characteristics of the solar wind in the Earth's orbit

Speed	400 km/s
Proton Density	6 cm -3
Proton temperature	To
Electron temperature	To
Magnetic field strength	E
Proton Flux Density	cm -2 s -1
Kinetic energy flux density	0.3 ergsm -2 s -1

S.v. flows can be divided into two classes: slow - with a speed of km / s and fast - with a speed of 600-700 km / s. Fast streams come from those regions of the corona where the magnetic field is close to radial. Some of these areas yavl. . Slow flows S.v. associated, apparently, with areas of the crown, where there is a means. tangential magnetic component. 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). In the analysis of gases captured in foils exposed to the Moon, Ne and Ar atoms were found. Average chem. composition of S.v. is given in table. 2.

Table 2. Relative chemical composition of the solar wind

Element	Relative content
H	0,96
3He
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 lines of force of this field frozen into the plasma form the interplanetary magnetic field. field (MMP). Although the intensity of the IMF is small and its energy density is approx. 1% of kinetic S.V. energy, it plays an important role in the thermodynamics of S.V. and in the dynamics of interactions S.v. with the bodies of the solar system and flows of S.v. between themselves. S.v. expansion combination with the rotation of the Sun leads to the fact that the magn. power lyonies frozen in the S.V. have a shape close to Archimedes' spirals (Fig. 2). Radial and azimuthal components of the magn. fields near the plane of the ecliptic change with distance:
,
where R- heliocentric. distance, - angular velocity of rotation of the Sun, u R- radial component of S.V. velocity, index "0" corresponds to the initial level. At a distance of the Earth's orbit, the angle between the directions of the magnetic. 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 orientations of the magnetic. fields, forms flows in differently oriented IMF - the so-called. interplanetary magnetic field.

In S.v. various types of waves are observed: Langmuir, whistlers, ionosonic, magnetosonic, etc. (see). Some of the waves are generated on the Sun, some are excited in the interplanetary medium. The generation of waves smooths out the deviations of the particle distribution function from the Maxwellian and leads to the fact that the S.V. behaves like a continuum. Waves of the Alfvén type play an important role in the acceleration of small components of the r.v. and in the formation of the proton distribution function. In S.v. contact and rotational discontinuities are also observed, which are characteristic of a magnetized plasma.

Flow S.V. yavl. supersonic in relation to the speed of those types of waves, to-rye provide efficient energy transfer in S.v. (Alfvén, sound and magnetosonic waves), Alfvén and sound Mach numbers S.v. in Earth's orbit. When obtrekanie 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. is decelerated and heated at the front of the shock wave, which allows it to flow around an obstacle. At the same time, in S.v. a cavity is formed - the magnetosphere (own or induced), the shape and size of the swarm is determined by the balance of pressure of the magnet. the planet's field and the pressure of the flowing plasma stream (see ). The layer of heated plasma between the shock wave and the streamlined obstacle is called. transition area. 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 yavl. , the thermalization of the flow of which is provided 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 the case of interaction 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 S.v. gradually filled with plasma is formed. 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), which gradually slows down as the S.V. moves through the plasma. The arrival of the shock wave to the Earth leads to compression of the magnetosphere, after which the development of the magnetic field usually begins. storms.

The equation describing the expansion of the solar corona can be obtained from the system of equations for the conservation of 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 corona. The choice between these two solutions is determined by the conditions at infinity. Solution 1 corresponds to low coronal expansion rates ("solar breeze", according to J. Chamberlain, USA) and gives high pressure values at infinity, i.e. encounters the same difficulties as the static model. crowns. Solution 2 corresponds to the passage of the expansion velocity through the value of the speed of sound ( v K) on some critical distance R K and subsequent expansion at supersonic speeds. This solution gives a vanishingly small value of the pressure at infinity, which makes it possible to match 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 exponent. On fig. 5 shows the change in expansion rate with heliocentric. distance depending on the temperature isothermal. isotropic corona. Subsequent models of S.v. take into account variations in the coronal temperature with distance, two-fluid character of the medium (electron and proton gases), thermal conductivity, viscosity, non-spherical nature of the expansion. Approach to the substance S.v. as to a continuous medium is justified by the presence of IMF and the collective nature of the interaction of S.V. plasma, due to various types of instabilities. S.v. provides the main the outflow of thermal energy of the corona, as heat transfer to the chromosphere, electromagnet. radiation of strongly ionized corona matter and electronic thermal conductivity S.V. insufficient to establish thermal. crown balance. Electronic thermal conductivity provides a slow decrease in the temperature of S.V. with distance. S.v. does not play any significant role in the energy of the Sun as a whole, because the energy flux carried away by it is ~ 10 -8

Imagine that you heard the words of the announcer in the weather forecast: “Tomorrow the wind will pick up sharply. In this regard, interruptions in the operation of radio, mobile communications and the Internet are possible. 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! And you can’t call it a refreshing “breeze” - 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, forecasters say 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. BUT sunny 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?

Solar wind and Earth's magnetosphere.

Sunny wind ( solar wind) is a stream of mega-ionized particles (mainly helium-hydrogen plasma) flowing from the solar corona at a speed of 300-1200 km/s into the surrounding space. It is one of the main components of the interplanetary medium.

Many natural phenomena are associated with the solar wind, including space weather phenomena such as magnetic storms and auroras.

The concepts of "solar wind" (a stream of ionized particles flying from the Sun to 2-3 days) and "sunshine" (a stream of photons flying from the Sun to the Earth in an average of 8 minutes 17 seconds) should not be confused. In particular, it is the effect of sunlight pressure (and not wind) that is used in the projects of the so-called solar sails. A form of engine for using an impulse of solar wind ions as a thrust source - an electric sail.

Story

The existence of a constant stream of particles flying from the Sun was first proposed by the British astronomer Richard Carrington. In 1859, Carrington and Richard Hodgson independently observed what was later called a solar flare. The following day, a geomagnetic storm occurred, and Carrington suggested a connection between these phenomena. Later, George Fitzgerald suggested that matter is periodically accelerated by the Sun and reaches the Earth in a few days.

In 1916, the Norwegian explorer Christian Birkeland wrote: "From a physical point of view, it is most probable that the rays of the sun are neither positive nor negative, but both." In other words, the solar wind is made up of negative electrons and positive ions.

Three years later, in 1919, Friederik Lindemann also suggested that particles of both charges, protons and electrons, come from the Sun.

In the 1930s, scientists determined that the temperature of the solar corona must reach a million degrees, since the corona remains bright enough at a great distance from the Sun, which is clearly visible during solar eclipses. Later spectroscopic observations confirmed this conclusion. In the mid-1950s, British mathematician and astronomer Sidney Chapman determined the properties of gases at such temperatures. It turned out that the gas becomes an excellent conductor of heat and should dissipate it into space beyond the Earth's orbit. At the same time, German scientist Ludwig Biermann became interested in the fact that comet tails always point away from the Sun. Biermann postulated that the Sun emits a constant stream of particles that pressurize the gas surrounding the comet, forming a long tail.

In 1955, Soviet astrophysicists S. K. Vsekhsvyatsky, G. M. Nikolsky, E. A. Ponomarev and V. I. Cherednichenko showed that an extended corona loses energy to radiation and can be in a state of hydrodynamic equilibrium only with a special distribution of powerful internal energy sources. In all other cases, there must be a flow of matter and energy. This process serves as a physical basis for an important phenomenon - the "dynamic corona". The magnitude of the flux of matter was estimated from the following considerations: if the corona were in hydrostatic equilibrium, then the heights of a homogeneous atmosphere for hydrogen and iron would be related as 56/1, that is, iron ions should not be observed in the far corona. But it's not. Iron glows throughout the corona, with FeXIV observed in higher layers than FeX, although the kinetic temperature is lower there. The force that maintains the ions in a "suspended" state can be the momentum transmitted during collisions by the ascending proton flux to the iron ions. From the condition of the balance of these forces, it is easy to find the flux of protons. It turned out to be the same as that followed from the hydrodynamic theory, subsequently confirmed by direct measurements. For 1955, this was a significant achievement, but no one then believed in the "dynamic crown".

Three years later, Eugene Parker concluded that the hot current from the Sun in Chapman's model and the stream of particles blowing away cometary tails in Biermann's hypothesis are two manifestations of the same phenomenon, which he called "solar wind". Parker showed that even though the solar corona is strongly attracted by the Sun, it conducts heat so well that it remains hot at great distances. Since its attraction weakens with distance from the Sun, a supersonic outflow of matter into interplanetary space begins from the upper corona. Moreover, Parker was the first to point out that the effect of weakening gravity has the same effect on the hydrodynamic flow as the Laval nozzle: it produces a transition of the flow from the subsonic to the supersonic phase.

Parker's theory has been heavily criticized. An article submitted in 1958 to the Astrophysical Journal was rejected by two reviewers and only thanks to the editor, Subramanyan Chandrasekhar, made it to the pages of the journal.

However, in January 1959, the first direct measurements of the characteristics of the solar wind (Konstantin Gringauz, IKI RAS) were carried out by the Soviet Luna-1, using a scintillation counter and a gas ionization detector installed on it. Three years later, the same measurements were carried out by the American Marcia Neugebauer using data from the Mariner-2 station.

Yet the acceleration of the wind to high speeds was not yet understood and could not be explained from Parker's theory. The first numerical models of the solar wind in the corona using the equations of magnetohydrodynamics were created by Pneumann and Knopp in 1971.

In the late 1990s, using the Ultraviolet Coronal Spectrometer ( Ultraviolet Coronal Spectrometer (UVCS) ) observations were made on board of the regions where the fast solar wind originates at the solar poles. It turned out that the wind acceleration is much greater than expected from purely thermodynamic expansion. Parker's model predicted that the wind speed becomes supersonic at 4 solar radii from the photosphere, and observations have shown that this transition occurs much lower, at about 1 solar radii, confirming that there is an additional mechanism for accelerating the solar wind.

Characteristics

The heliospheric current sheet is the result of the influence of the Sun's rotating magnetic field on the plasma in the solar wind.

Due to the solar wind, the Sun loses about one million tons of matter every second. The solar wind consists mainly of electrons, protons, and helium nuclei (alpha particles); the nuclei of other elements and non-ionized particles (electrically neutral) are contained in a very small amount.

Although the solar wind comes from the outer layer of the Sun, it does not reflect the real composition of the elements in this layer, since as a result of differentiation processes, the abundance of some elements increases and some decreases (FIP effect).

The intensity of the solar wind depends on changes in solar activity and its sources. Long-term observations in the Earth's orbit (about 150 million km from the Sun) have shown that the solar wind is structured and is usually divided into calm and disturbed (sporadic and recurrent). Calm flows, depending on the speed, are divided into two classes: slow(approximately 300-500 km / s near the Earth's orbit) and fast(500-800 km/s near the Earth's orbit). Sometimes the region of the heliospheric current sheet, which separates regions of different polarity of the interplanetary magnetic field, is referred to as a stationary wind, and is close in its characteristics to a slow wind.

slow solar wind

The slow solar wind is generated by the "calm" part of the solar corona (the region of coronal streamers) during its gas-dynamic expansion: at a corona temperature of about 2 10 6 K, the corona cannot be in hydrostatic equilibrium, and this expansion, under the existing boundary conditions, should lead to acceleration of the matter to supersonic speeds. The heating of the solar corona to such temperatures occurs due to the convective nature of heat transfer in the solar photosphere: the development of convective turbulence in the plasma is accompanied by the generation of intense magnetosonic waves; in turn, when propagating in the direction of decreasing the density of the solar atmosphere, sound waves are transformed into shock waves; shock waves are effectively absorbed by the material of the corona and heat it up to a temperature of (1-3) 10 6 K.

fast solar wind

Streams of the recurrent fast solar wind are emitted by the Sun for several months and have a return period of 27 days (the rotation period of the Sun) when observed from the Earth. These streams are associated with coronal holes - regions of the corona with a relatively low temperature (approximately 0.8·10 6 K), reduced plasma density (only a quarter of the density of quiet regions of the corona) and a magnetic field radial with respect to the Sun.

Disturbed flows

Disturbed flows include the interplanetary manifestation of coronal mass ejections (CMEs), as well as compression regions ahead of fast CMEs (called Sheath in the English literature) and ahead of fast flows from coronal holes (called the Corotating interaction region - CIR in the English literature). About half of the cases of Sheath and CIR observations may have an interplanetary shock ahead of them. It is in perturbed solar wind types that the interplanetary magnetic field can deviate from the ecliptic plane and contain a southern field component, which leads to many effects of space weather (geomagnetic activity, including magnetic storms). Disturbed sporadic outflows were previously thought to be caused by solar flares, but sporadic outflows in the solar wind are now believed to be due to CMEs. At the same time, it should be noted that both solar flares and coronal mass ejections are associated with the same energy sources on the Sun and there is a statistical relationship between them.

According to the observation time of various large-scale solar wind types, fast and slow streams make up about 53%, the heliospheric current sheet 6%, CIR - 10%, CME - 22%, Sheath - 9%, and the ratio between the observation time of various types varies greatly in the solar cycle. activity.

Phenomena generated by the solar wind

Due to the high conductivity of the solar wind plasma, the solar magnetic field is frozen into the outflowing wind currents and is observed in the interplanetary medium in the form of an interplanetary magnetic field.

The solar wind forms the boundary of the heliosphere, due to which it prevents penetration into. The magnetic field of the solar wind significantly weakens the galactic cosmic rays coming from outside. A local increase in the interplanetary magnetic field leads to short-term decreases in cosmic rays, Forbush decreases, and large-scale field decreases lead to their long-term increases. Thus, in 2009, during the period of a protracted minimum of solar activity, the intensity of radiation near the Earth increased by 19% relative to all previously observed maxima.

The solar wind generates in the solar system, possessing a magnetic field, phenomena such as the magnetosphere, aurora and radiation belts of planets.

Constant radial flux of solar plasma. crowns in interplanetary production. The flow of energy coming from the bowels of the Sun heats the plasma of the corona up to 1.5-2 million K. Post. heating is not balanced by the loss of energy due to radiation, since the corona is small. Excess energy means. degree carry away h-tsy S. century. (=1027-1029 erg/s). The crown, therefore, is not in hydrostatic. equilibrium, it is constantly expanding. According to the composition of S. century. does not differ from the plasma of the corona (S. century contains chiefly arr. protons, electrons, a few helium nuclei, oxygen ions, silicon, sulfur, and iron). At the base of the corona (10,000 km from the solar photosphere) h-tsy have a radial order of hundreds of m / s, at a distance of several. solar radii, it reaches the speed of sound in plasma (100 -150 km / s), near the Earth's orbit, the speed of protons is 300-750 km / s, and their space. - from several h-ts up to several tens of fractions in 1 cm3. With the help of interplanetary space. stations found that up to the orbit of Saturn, the density flow h-c S. v. decreases according to the law (r0/r)2, where r is the distance from the Sun, r0 is the initial level. S. v. carries with it the loops of the lines of force of the suns. magn. fields, to-rye form interplanetary magn. . combination of radial ch-c movements S. v. with the rotation of the Sun gives these lines the shape of spirals. Large-scale structure of the magnet. The field in the vicinity of the Sun has the form of sectors, in which the field is directed away from the Sun or towards it. The size of the cavity occupied by the SV is not exactly known (its radius, apparently, is not less than 100 AU). At the boundaries of this cavity dynamic. S. v. must be balanced by the pressure of interstellar gas, galactic. magn. fields and galactic space rays. In the vicinity of the Earth, the collision of the flow of c-c S. v. with geomagnetic field generates a stationary shock wave in front of the Earth's magnetosphere (from the side of the Sun, Fig.).

S. v. as if it flows around the magnetosphere, limiting its extent in the pr-ve. Changes in the intensity of S. century associated with solar flares, yavl. main the cause of geomagnetic disturbances. fields and magnetospheres (magnetic storms).

Over the Sun loses with S. in. \u003d 2X10-14 part of its mass Msun. It is natural to assume that an outflow of water, similar to S. V., also exists in other stars (""). It should be especially intense for massive stars (with a mass = several tens of Msolns) and with a high surface temperature (= 30-50 thousand K) and for stars with an extended atmosphere (red giants), because in In the first case, parts of a highly developed stellar corona have a sufficiently high energy to overcome the attraction of the star, and in the second, they have a low parabolic. speed (escape speed; (see SPACE SPEEDS)). Means. mass losses with the stellar wind (= 10-6 Msol/yr and more) can significantly affect the evolution of stars. In turn, the stellar wind creates "bubbles" of hot gas in the interstellar medium - sources of X-rays. radiation.

Physical Encyclopedic Dictionary. - M.: Soviet Encyclopedia. . 1983 .

SOLAR WIND - a continuous flow of plasma of solar origin, the 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 substance, and the corona expands.

The first evidence of the existence of post. plasma flux from the Sun obtained by L. Birman (L. Biermann) in the 1950s. on the analysis of the forces acting on the plasma tails of comets. In 1957, J. Parker (E. Parker), analyzing the equilibrium conditions of the substance of the crown, showed that the crown cannot be in hydrostatic conditions. Wed S.'s characteristics are given in table. 1. Flows of S. in. 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 streams come from regions of the solar corona, where the structure of the magnetic. field is close to radial. coronal holes. Slow streams. in. associated, apparently, with the areas of the crown, in which there is a means Tab. one. - Average characteristics of the solar wind in Earth's orbit

Speed
Proton concentration
Proton temperature
Electron temperature
Magnetic field strength
Python Flux Density....	2.410 8 cm -2 c -1
Kinetic energy flux density	0.3 ergcm -2 s -1

Tab. 2.- Relative chemical composition of the solar wind

	Relative content

	Relative content

In addition to the main the components of S. century - protons and electrons, - particles were also found in its composition. Measurements of ionization. temperature of ions S. century. make it possible to determine the electron temperature of the solar corona.

In S. century. differences are observed. types of waves: Langmuir, whistlers, ion-sound, Plasma waves). Some of the Alfvén type waves are generated on the Sun, and some are excited in the interplanetary medium. The generation of waves smooths out the deviations of the function of the distribution of particles from the Maxwellian and, in conjunction with the influence of the magnetic. field on the plasma leads to the fact that S. century. behaves like a continuum. Waves of the Alfvén type play a large role in the acceleration of the small components of C.

Rice. 1. Massive solar wind. On the horizontal axis - the ratio of the mass of the particle to its charge, on the vertical - the number of particles registered in the energy window of the device for 10 s. The numbers with a "+" sign indicate the charge of the ion.

S.'s stream in. is supersonic in relation to the speeds of those types of waves, to-rye provide eff. energy transfer in S. century. (Alvenov, sound). Alvenovskoye and sound Mach number C. in. 7. When flowing around S. in. obstacles capable of effectively deflecting it (the magnetic fields of Mercury, Earth, Jupiter, Saturn or the conducting ionospheres of Venus and, apparently, Mars), an outgoing bow shock wave is formed. waves, which allows it to flow around an obstacle. At the same time in S. century. a cavity is formed - the magnetosphere (own or induced), the shape and size of the swarm are determined by the balance of magnetic pressure. field of the planet and the pressure of the flowing plasma flow (see Fig. Magnetosphere of the Earth, Magnetosphere of planets). In the case of interaction S. century. with a non-conducting body (eg, 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 C. in.

The stationary process of corona plasma outflow is superimposed by nonstationary processes associated with flares on the sun. With strong outbreaks, matter is ejected from the bottom. regions of the corona into the interplanetary medium. magnetic variations).

Rice. 2. Propagation of an interplanetary shock wave and ejecta from a solar flare. The arrows show the direction of motion of the solar wind plasma,

Rice. 3. Types of solutions to the corona expansion equation. The speed and distance are normalized to the critical speed vc and the critical distance Rc. Solution 2 corresponds to the solar wind.

The expansion of the solar corona is described by a system of ur-tions of conservation of mass, v k) on some critical. distance R to and subsequent expansion at supersonic speed. This solution gives a vanishingly small value of the pressure at infinity, which makes it possible to match it with the low pressure of the interstellar medium. Yu. Parker called the course of this type S. century. , where m is the mass of the proton, is the adiabatic index, is the mass of the Sun. On fig. 4 shows the change in expansion rate with heliocentric. thermal conductivity, viscosity,

Rice. 4. Solar wind velocity profiles for the isothermal corona model at various values of coronal temperature.

S. v. provides the main outflow of thermal energy of the corona, since heat transfer to the chromosphere, el.-mag. coronas and electronic thermal conductivitypp. in. insufficient to establish the thermal balance of the corona. Electronic thermal conductivity provides a slow decrease in the temperature of S. in. with distance. luminosity of the sun.

where - ang. sun rotation speed and - radial component of velocity c., index 0 corresponds to the initial level. At a distance of the Earth's orbit, the angle between the direction of the magnetic. fields and R about 45°. At large L magn.

Rice. 5. The shape of the field line of the interplanetary magnetic field. - the angular velocity of the rotation of the Sun, and - the radial component of the plasma velocity, R - the heliocentric distance.

S. v., arising over the regions of the Sun with decomp. magnetic orientation. fields, speed, temp-pa, concentration of particles, etc.) also cf. regularly change in the cross section of each sector, which is associated with the existence of a fast S. flow within the sector. The boundaries of the sectors are usually located in the intraslow flow of S. at. Most often, 2 or 4 sectors are observed, rotating with the Sun. This structure which is formed at S.'s pulling out of century. large-scale magnetic field of the crown, can be observed for several. revolutions of the sun. The sectoral structure of the IMF is a consequence of the existence of a current sheet (TS) in the interplanetary medium, which rotates together with the Sun. TS creates a magnetic surge. fields - radial IMF have different signs on different sides of the vehicle. This TS, predicted by H. Alfven, passes through those parts of the solar corona, which are associated with active regions on the Sun, and separates these regions from decomp. signs of the radial component of the solar magnet. fields. The TC 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 CS folds into a spiral (Fig. 6). Being near the plane of the ecliptic, the observer turns out to be either above or below the CS, due to which he falls into sectors with different signs of the IMF radial component.

Near the Sun in the N. century. there are longitudinal and latitudinal velocity gradients of collisionless shock waves (Fig. 7). First, a shock wave is formed that propagates forward from the boundary of the sectors (a direct shock wave), and then a reverse shock wave is formed that propagates towards the Sun.

Rice. 6. Shape of the heliospheric current sheet. Its intersection with the plane of the ecliptic (tilted to the equator of the Sun at an angle of ~ 7°) gives the observed sectoral structure of the interplanetary magnetic field.

Rice. 7. Structure of the sector of the interplanetary magnetic field. The short arrows show the direction of the solar wind, the arrow lines show the magnetic field lines, the dash-dotted line shows the sector boundaries (the intersection of the figure plane with the current sheet).

Since the speed of the shock wave is less than the speed of the SV, it carries away 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, like interplanetary shock waves from solar flares and circumplanetary shock waves, accelerate particles and are thus a source of energetic particles.

S. v. extends to distances of ~100 AU. That is, where the pressure of the interstellar medium balances the dynamic. S.'s pressure The cavity swept up by S. in. interplanetary environment). ExpandingS. in. together with the magnet frozen into it. field prevents penetration into the solar system galactic. space rays of low energies and leads to cosmic variations. beams of high energy. A phenomenon similar to S. V., found in some other stars (see. Stellar wind).

Lit.: Parker E. N., Dynamics in the interplanetary medium, O. L. Vaisberg.

Physical encyclopedia. In 5 volumes. - M.: Soviet Encyclopedia. Editor-in-Chief A. M. Prokhorov. 1988 .

See what "SOLAR WIND" is in other dictionaries:

SOLAR WIND, the solar corona plasma flow that fills the solar system up to a distance of 100 astronomical units from the Sun, where the pressure of the interstellar medium balances the dynamic pressure of the flow. The main composition is protons, electrons, nuclei ... Modern Encyclopedia

SOLAR WIND, a steady flow of charged particles (mainly protons and electrons) accelerated by the high temperature of the solar CORONA to speeds large enough for the particles to overcome the gravity of the Sun. The solar wind deflects... Scientific and technical encyclopedic dictionary

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 be assumed 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. Calculations made by physicists showed irrefutably that a change in 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 solar system, and, moreover, those 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. By the way, 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 of 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 with them and magnetic fields. 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 exactly 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.