What speed does the solar wind reach near the earth? What is the solar wind? Influence of solar wind

Imagine that you heard the words of a weather forecast announcer: “Tomorrow the wind will increase sharply. In this regard, interruptions in the operation of radio, mobile communications and the Internet are possible. The US space mission has been delayed. Intense auroras are expected in northern 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: “Yesterday night there was a flare on the Sun. 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 don’t delve into hundreds of cumbersome formulas, calculations and heated scientific debates, then, in general, the picture seems like this.

There are thermonuclear reactions going on inside our star, 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 so fast that when they collide, they smash each other to pieces. It is known that 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 gain increasing speed and reach near-Earth boundaries in about six days. Even if the sun was calm, the speed of the solar wind here reaches 450 kilometers per second. Well, when a solar flare spews out a huge fiery bubble of particles, their speed can reach 1200 kilometers per second! And the “breeze” cannot be called refreshing - about 200 thousand degrees.

Can a person feel the solar wind?

Indeed, since a stream of hot particles is constantly rushing, why don’t we feel how it “blows” us? Let's say the particles are so small that the skin does not feel their touch. But they are not noticed by earthly instruments either. Why?

Because the Earth is protected from solar vortices by its magnetic field. The flow of particles seems to flow around it and rush on. Only on days when solar emissions are especially powerful does our magnetic shield have a hard time. A solar hurricane breaks through it and bursts into the upper atmosphere. Alien particles cause . The magnetic field is sharply deformed, weather forecasters talk about “magnetic storms.”


Because of them, space satellites go out of control. Airplanes disappear from 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. An electric current suddenly appears in power grids, railway rails, and pipelines. As a result, traffic lights switch on their own, gas pipelines rust, and disconnected electrical appliances burn out. Plus, thousands of people feel discomfort and illness.

The cosmic effects of the solar wind can be detected not only during solar flares: although it is weaker, it blows constantly.

It has long been noted that the tail of a comet grows as it approaches the Sun. It causes the frozen gases that form the comet's nucleus to evaporate. And the solar wind carries these gases away in the form of a plume, always directed in the direction opposite to the Sun. This is how the earth's wind turns the smoke from the chimney and gives it one shape or another.

During years of increased activity, the Earth's exposure to galactic cosmic rays drops sharply. The solar wind gains such strength that it simply sweeps them to the outskirts of the planetary system.

There are planets that have a very weak magnetic field, or even none at all (for example, on Mars). There’s nothing stopping the solar wind from running wild here. 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 die down?

Nobody knows the exact answer yet. Particles fly to the outskirts of the Earth, gaining speed. Then it gradually falls, but the wind seems to reach the farthest corners of the solar system. Somewhere there it weakens and is slowed down by rarefied interstellar matter.

So far, astronomers cannot say exactly how far away this occurs. To answer, you need to catch particles, flying further and further from the Sun until they stop coming across. By the way, the limit where this happens can be considered the boundary of the Solar system.


Spacecraft that are periodically launched from our planet are equipped with solar wind traps. In 2016, solar wind flows were captured on video. Who knows if he won’t become as familiar a “character” in weather reports as our old friend – the earth’s wind?

Constant radial flow of solar plasma. crowns in interplanetary production. The flow of energy coming from the depths of the Sun heats the corona plasma to 1.5-2 million K. DC. heating is not balanced by energy loss due to radiation, since the corona is small. Excess energy means. degrees are carried away by the S. century. (=1027-1029 erg/s). The crown, therefore, is not in a hydrostatic position. equilibrium, it continuously expands. According to the composition of the S. century. does not differ from corona plasma (solar plasma contains mainly protons, electrons, some helium nuclei, oxygen, silicon, sulfur, and iron ions). At the base of the corona (10 thousand km from the photosphere of the Sun), particles have a radial radial of the 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 spaces. - from several h-ts to several tens of ppm in 1 cm3. With the help of interplanetary space. stations, it has been established that up to the orbit of Saturn, the flux density of the 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 solar power lines. mag. fields, which form the interplanetary magnetic field. . The combination of radial movement h-c S. v. with the rotation of the Sun it gives these lines the shape of spirals. Large-scale structure of mag. The fields in the vicinity of the Sun have the form of sectors, in which the field is directed from the Sun or towards it. The size of the cavity occupied by the S. v. is not precisely known (its radius is apparently no less than 100 AU). At the boundaries of this cavity there is a dynamic S.v. must be balanced by the pressure of interstellar gas, galactic. mag. fields and galactic space rays. In the vicinity of the Earth, the collision of the flow of h-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. flows around the magnetosphere, as it were, limiting its extent in space. Changes in solar intensity associated with solar flares, phenomena. basic cause of geomagnetic disturbances. fields and magnetosphere (magnetic storms).

Behind the Sun it loses from the north. =2X10-14 part of its mass Msol. It is natural to assume that the outflow of matter, similar to the S.E., also exists in other stars (""). It should be especially intense in massive stars (with mass = several tens of Msolns) and with high surface temperatures (= 30-50 thousand K) and in stars with an extended atmosphere (red giants), because in In the first case, the particles of a highly developed stellar corona have a sufficiently high energy to overcome the gravity of the star, and in the second, the parabolic energy is low. speed (escaping speed; (see SPACE SPEEDS)). Means. Mass losses with stellar wind (= 10-6 Msol/year 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 flows from the Sun were obtained by L. 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 conditions of equilibrium of the corona matter, showed that the corona cannot be in hydrostatic conditions. 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. coronal holes. Slow streamspp. V. are apparently associated with the areas of the crown, in which there is, therefore, Table 1. - Average characteristics of the solar wind in Earth orbit

Table 2.- Relative chemical composition of the solar wind

In addition to the main components of solar water - protons and electrons; particles were also found in its composition. Measurements of ionization. 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-acoustic, 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 to 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 S.

Rice. 1. Massive 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). Alfven and sound Mach number C. V. 7. When flowing around the north side. 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. waves, which allows it to flow around an 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 magnetic pressure balance. 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, gradually filled with plasma C. V.

The stationary process of corona plasma outflow is superimposed by non-stationary processes associated with flares on the Sun. During strong flares, substances are released from the bottom. corona regions into the interplanetary medium. Magnetic variations).

Rice. 2. Propagation of an interplanetary shock wave and ejection from a solar flare. The arrows indicate 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 vk and the critical distanceRk. Solution 2 corresponds to the solar wind.

The expansion of the solar corona is described by a system of mass conservation equations, v k) at some critical point. 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. , 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. thermal conductivity, viscosity,

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. coronas and electronic thermal conductivitypp. V. are insufficient to establish the thermal balance of the corona. Electronic thermal conductivity ensures a slow decrease in the ambient temperature. with distance. luminosity of the Sun.

S.v. carries the coronal magnetic field with it into the interplanetary medium. field. The force lines of this field frozen into the plasma form an interplanetary magnetic field. field (IMF). Although the intensity of the IMF is low and its energy density is about 1% of the kinetic density. energy of solar energy, it plays an important role in thermodynamics. V. 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 of the century have the form 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 velocityC. c., index 0 corresponds to the initial level. At the distance of the Earth's orbit, the angle between the magnetic direction. fields and R about 45°. At large L magnetic.

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, speed, temp-pa, particle concentration, etc.) also in cf. change naturally in the cross section of each sector, which is associated with the existence of a fast flow of solar water within the sector. The boundaries of the sectors are usually located within the slow flow of the North century. Most often, 2 or 4 sectors are observed, rotating with the Sun. This structure, formed when the S. is pulled out. large-scalemagn. 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 sheet (CS) 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 TC, 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 different ones. 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 falls into sectors with different signs of the IMF radial component.

Near the Sun in the north. there are longitudinal and latitudinal gradients of the velocity of collisionless shock waves (Fig. 7). First, a shock wave is formed, propagating forward from the boundary of the sectors (direct 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 the solar wind, arrowed lines indicate magnetic field lines, dash-dotted lines indicate the boundaries of the sector (the intersection of the drawing plane with the current layer).

Since the speed of the shock wave is less than the speed of the solar wind, it carries the reverse shock wave in the direction away from the Sun. Shock waves near 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. Interplanetary environment). ExpandingS. 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 cosmic variations. high energy rays. A phenomenon similar to the S.V. has been discovered in some other stars (see. Stellar wind).

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

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, a stream of plasma from the solar corona 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 stream. The main composition is protons, electrons, nuclei... Modern encyclopedia

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

There is a constant stream of particles ejected from the Sun's upper atmosphere. 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.

Solar wind speed online near Earth, data for the last 3 days

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.

In 1957, University of Chicago professor E. Parker theoretically predicted the phenomenon, which was called the “solar wind.” It took two years for this prediction to be confirmed experimentally using instruments installed on the Soviet Luna-2 and Luna-3 spacecraft by K.I. Gringauz’s group. What is this phenomenon?

The solar wind is a stream of fully ionized hydrogen gas, usually called fully ionized hydrogen plasma due to the approximately equal density of electrons and protons (quasineutrality condition), which accelerates away from the Sun. In the region of the Earth's orbit (at one astronomical unit or 1 AU from the Sun), its speed reaches an average value of V E » 400–500 km/sec at a proton temperature T E » 100,000 K and a slightly higher electron temperature (index “E” here and in hereinafter refers to the Earth's orbit). At such temperatures, the speed is significantly higher than the speed of sound by 1 AU, i.e. The flow of solar wind in the region of the Earth's orbit is supersonic (or hypersonic). The measured concentration of protons (or electrons) is quite small and amounts to n E » 10–20 particles per cubic centimeter. In addition to protons and electrons, alpha particles (of the order of several percent of the proton concentration), a small amount of heavier particles, as well as an interplanetary magnetic field were discovered in interplanetary space, the average induction value of which turned out to be on the order of several gammas in Earth’s orbit (1g = 10 –5 gauss).

The collapse of the idea of ​​a static solar corona.

For quite a long time, it was believed that all stellar atmospheres are in a state of hydrostatic equilibrium, i.e. in a state where the force of gravitational attraction of a given star is balanced by the force associated with the pressure gradient (the change in pressure in the star’s atmosphere at a distance r from the center of the star. Mathematically, this equilibrium is expressed as an ordinary differential equation,

Where G– gravitational constant, M* – mass of the star, p and r – pressure and mass density at some distance r from the star. Expressing mass density from the equation of state for an ideal gas

R= r RT

through pressure and temperature and integrating the resulting equation, we obtain the so-called barometric formula ( R– gas constant), which in the particular case of constant temperature T looks like

Where p 0 – represents the pressure at the base of the star’s atmosphere (at r = r 0). Since before Parker’s work it was believed that the solar atmosphere, like the atmospheres of other stars, was in a state of hydrostatic equilibrium, its state was determined by similar formulas. Taking into account the unusual and not yet fully understood phenomenon of a sharp increase in temperature from approximately 10,000 K on the surface of the Sun to 1,000,000 K in the solar corona, S. Chapman developed the theory of a static solar corona, which was supposed to smoothly transition into the local interstellar medium surrounding the Solar system. It followed that, according to the ideas of S. Chapman, the Earth, making its revolutions around the Sun, is immersed in a static solar corona. This point of view has been shared by astrophysicists for a long time.

Parker dealt a blow to these already established ideas. He drew attention to the fact that the pressure at infinity (at r® Ґ), which is obtained from the barometric formula, is almost 10 times greater in magnitude than the pressure that was accepted at that time for the local interstellar medium. To eliminate this discrepancy, E. Parker suggested that the solar corona cannot be in hydrostatic equilibrium, but must continuously expand into the interplanetary medium surrounding the Sun, i.e. radial speed V solar corona is not zero. Moreover, instead of the equation of hydrostatic equilibrium, he proposed using a hydrodynamic equation of motion of the form, where M E is the mass of the Sun.

For a given temperature distribution T, as a function of distance from the Sun, solving this equation using the barometric formula for pressure and the mass conservation equation in the form

can be interpreted as the solar wind and precisely with the help of this solution with the transition from subsonic flow (at r r *) to supersonic (at r > r*) pressure can be adjusted R with pressure in the local interstellar medium, and, therefore, it is this solution, called the solar wind, that is carried out in nature.

The first direct measurements of the parameters of interplanetary plasma, which were carried out on the first spacecraft entering interplanetary space, confirmed the correctness of Parker’s idea about the presence of supersonic solar wind, and it turned out that already in the region of the Earth’s orbit the speed of the solar wind far exceeds the speed of sound. Since then, there has been no doubt that Chapman's idea of ​​​​the hydrostatic equilibrium of the solar atmosphere is erroneous, and the solar corona is continuously expanding at supersonic speed into interplanetary space. Somewhat later, astronomical observations showed that many other stars have “stellar winds” similar to the solar wind.

Despite the fact that the solar wind was predicted theoretically based on a spherically symmetric hydrodynamic model, the phenomenon itself turned out to be much more complex.

What is the real pattern of solar wind movement? For a long time, the solar wind was considered spherically symmetric, i.e. independent of solar latitude and longitude. Since spacecraft before 1990, when the Ulysses spacecraft was launched, mainly flew in the ecliptic plane, measurements on such spacecraft gave distributions of solar wind parameters only in this plane. Calculations based on observations of the deflection of cometary tails indicated an approximate independence of solar wind parameters from solar latitude, however, this conclusion based on cometary observations was not sufficiently reliable due to the difficulties in interpreting these observations. Although the longitudinal dependence of solar wind parameters was measured by instruments installed on spacecraft, it was nevertheless either insignificant and associated with the interplanetary magnetic field of solar origin, or with short-term non-stationary processes on the Sun (mainly with solar flares).

Measurements of plasma and magnetic field parameters in the ecliptic plane have shown that so-called sector structures with different parameters of the solar wind and different directions of the magnetic field can exist in interplanetary space. Such structures rotate with the Sun and clearly indicate that they are a consequence of a similar structure in the solar atmosphere, the parameters of which thus depend on solar longitude. The qualitative four-sector structure is shown in Fig. 1.

At the same time, ground-based telescopes detect the general magnetic field on the surface of the Sun. Its average value is estimated at 1 G, although in individual photospheric formations, for example, in sunspots, the magnetic field can be orders of magnitude greater. Since plasma is a good conductor of electricity, solar magnetic fields somehow interact with the solar wind due to the appearance of ponderomotive force j ґ B. This force is small in the radial direction, i.e. it has virtually no effect on the distribution of the radial component of the solar wind, but its projection onto a direction perpendicular to the radial direction leads to the appearance of a tangential velocity component in the solar wind. Although this component is almost two orders of magnitude smaller than the radial one, it plays a significant role in the removal of angular momentum from the Sun. Astrophysicists suggest that the latter circumstance may play a significant role in the evolution not only of the Sun, but also of other stars in which a stellar wind has been detected. In particular, to explain the sharp decrease in the angular velocity of stars of the late spectral class, the hypothesis that they transfer rotational momentum to the planets formed around them is often invoked. The considered mechanism for the loss of angular momentum of the Sun by the outflow of plasma from it in the presence of a magnetic field opens up the possibility of revising this hypothesis.

Measurements of the average magnetic field not only in the region of the Earth's orbit, but also at large heliocentric distances (for example, on the Voyager 1 and 2 and Pioneer 10 and 11 spacecraft) showed that in the ecliptic plane, almost coinciding with the plane of the solar equator , its magnitude and direction are well described by the formulas

received by Parker. In these formulas, which describe the so-called Parkerian spiral of Archimedes, the quantities B r, B j – radial and azimuthal components of the magnetic induction vector, respectively, W – angular velocity of the Sun’s rotation, V– radial component of the solar wind, index “0” refers to the point of the solar corona at which the magnitude of the magnetic field is known.

The European Space Agency's launch of the Ulysses spacecraft in October 1990, whose trajectory was calculated so that it now orbits the Sun in a plane perpendicular to the ecliptic plane, completely changed the idea that the solar wind is spherically symmetric. In Fig. Figure 2 shows the distributions of radial velocity and density of solar wind protons measured on the Ulysses spacecraft as a function of solar latitude.

This figure shows a strong latitudinal dependence of solar wind parameters. It turned out that the speed of the solar wind increases, and the density of protons decreases with heliographic latitude. And if in the ecliptic plane the radial velocity is on average ~ 450 km/sec, and the proton density is ~15 cm–3, then, for example, at 75° solar latitude these values ​​are ~700 km/sec and ~5 cm–3, respectively. The dependence of solar wind parameters on latitude is less pronounced during periods of minimum solar activity.

Non-stationary processes in the solar wind.

The model proposed by Parker assumes the spherical symmetry of the solar wind and the independence of its parameters from time (stationarity of the phenomenon under consideration). However, the processes occurring on the Sun, generally speaking, are not stationary, and therefore the solar wind is not stationary. The characteristic times of changes in parameters have very different scales. In particular, there are changes in solar wind parameters associated with the 11-year cycle of solar activity. In Fig. Figure 3 shows the average (over 300 days) dynamic pressure of the solar wind measured using the IMP-8 and Voyager-2 spacecraft (r V 2) in the area of ​​the Earth’s orbit (at 1 AU) during one 11-year solar cycle of solar activity (upper part of the figure). On the bottom of Fig. Figure 3 shows the change in the number of sunspots over the period from 1978 to 1991 (the maximum number corresponds to the maximum solar activity). It can be seen that the parameters of the solar wind change significantly over a characteristic time of about 11 years. At the same time, measurements on the Ulysses spacecraft showed that such changes occur not only in the ecliptic plane, but also at other heliographic latitudes (at the poles the dynamic pressure of the solar wind is slightly higher than at the equator).

Changes in solar wind parameters can also occur on much smaller time scales. For example, flares on the Sun and different rates of plasma outflow from different regions of the solar corona lead to the formation of interplanetary shock waves in interplanetary space, which are characterized by a sharp jump in speed, density, pressure, and temperature. The mechanism of their formation is shown qualitatively in Fig. 4. When a fast flow of any gas (for example, solar plasma) catches up with a slower one, an arbitrary gap in the parameters of the gas appears at the point of their contact, in which the laws of conservation of mass, momentum and energy are not satisfied. Such a discontinuity cannot exist in nature and breaks up, in particular, into two shock waves (on them the laws of conservation of mass, momentum and energy lead to the so-called Hugoniot relations) and a tangential discontinuity (the same conservation laws lead to the fact that on it the pressure and the normal velocity component must be continuous). In Fig. 4 this process is shown in the simplified form of a spherically symmetrical flare. It should be noted here that such structures, consisting of a forward shock wave, a tangential discontinuity and a second shock wave (reverse shock), move from the Sun in such a way that the forward shock moves at a speed greater than the speed of the solar wind, the reverse shock moves from the Sun at a speed slightly lower than the speed of the solar wind, and the speed of the tangential discontinuity is equal to the speed of the solar wind. Such structures are regularly recorded by instruments installed on spacecraft.

On changes in solar wind parameters with distance from the sun.

The change in solar wind speed with distance from the Sun is determined by two forces: the force of solar gravity and the force associated with changes in pressure (pressure gradient). Since the force of gravity decreases as the square of the distance from the Sun, its influence is insignificant at large heliocentric distances. Calculations show that already in Earth's orbit its influence, as well as the influence of the pressure gradient, can be neglected. Consequently, the speed of the solar wind can be considered almost constant. Moreover, it significantly exceeds the speed of sound (hypersonic flow). Then from the above hydrodynamic equation for the solar corona it follows that the density r decreases as 1/ r 2. The American spacecraft Voyager 1 and 2, Pioneer 10 and 11, launched in the mid-1970s and now located at distances from the Sun of several tens of astronomical units, confirmed these ideas about the parameters of the solar wind. They also confirmed the theoretically predicted Parker Archimedes spiral for the interplanetary magnetic field. However, the temperature does not follow the adiabatic cooling law as the solar corona expands. At very large distances from the Sun, the solar wind even tends to warm up. Such heating may be due to two reasons: energy dissipation associated with plasma turbulence and the influence of neutral hydrogen atoms penetrating into the solar wind from the interstellar medium surrounding the solar system. The second reason also leads to some braking of the solar wind at large heliocentric distances, detected on the above-mentioned spacecraft.

Conclusion.

Thus, the solar wind is a physical phenomenon that is of not only purely academic interest associated with the study of processes in plasma located in the natural conditions of outer space, but also a factor that must be taken into account when studying processes occurring in the vicinity of the Earth, since these processes influence our lives to one degree or another. In particular, high-speed solar wind flows flowing around the Earth’s magnetosphere affect its structure, and non-stationary processes on the Sun (for example, flares) can lead to magnetic storms that disrupt radio communications and affect the well-being of weather-sensitive people. Since the solar wind originates in the solar corona, its properties in the region of the Earth’s orbit are a good indicator for studying solar-terrestrial connections that are important for practical human activity. However, this is another area of ​​scientific research, which we will not touch upon in this article.

Vladimir Baranov

People are getting more and more attention interesting facts about the solar wind. What is this phenomenon? In the late 1940s, savvy astrophysicists concluded that the Sun was collecting gaseous materials from interstellar space. For this reason, the theory was put forward about the existence of wind directed towards the sun. After some time, scientists were even able to confirm the existence of the solar wind, but with a slight amendment: the wind comes from the Sun in different directions. Let's look at some interesting facts about this phenomenon:

1. First of all, you need to know that the definition of “solar wind” describes an astrophysical phenomenon, not a meteorological one. This process is a continuous radiation of plasma into the surrounding space. Through this wind, the Sun seems to remove the excess energy contained in it.
2. In fact, instead of accumulating substances from the surrounding outer space, the Sun throws out in different directions the substance it contains in a volume equal to one million tons per period corresponding to one revolution of the Earth around its axis.
3. The speed of particles moving away from the Sun is constantly increasing, since they are pushed by similar matter, the temperature of which is much higher. In addition, the force of attraction of the Sun gradually ceases to act on plasma particles, which are components of the flows.

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4. At approximately 20,000 km from the surface, the speed of plasma particles can correspond to tens of thousands of meters per second. After traveling a distance corresponding to several diameters of the sun, the speed of the plasma particles becomes a thousand times greater. Near our planet, this speed becomes hundreds of times higher, and their density becomes much lower than that of the atmosphere.

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5. The flow mostly includes protons and electrons, but it also contains nuclei of helium and other elements.

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6. The temperature of plasma particles located at the very beginning of the solar wind flows corresponds to approximately two million degrees Kelvin. As you move away, the temperature first increases to 20 million degrees and only then begins to decrease. When the wind flows reach our planet, the plasma particles cool to about 10,000 degrees.
7. When solar flares occur, the temperature of the plasma near the Earth corresponds to 100 thousand degrees.

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8. Our planet's magnetic field protects us well from this radiation. Streams of solar winds literally flow around the earth's atmosphere and sweep further into the surrounding space, gradually reducing their density.
9. From time to time, the intensity of passing streams of plasma particles is so high that the atmosphere of our planet has difficulty reflecting their impact. Naturally, the solar wind flows recede, but only after some time.

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10. When powerful streams of solar winds interact intensively with the magnetic field of our planet, we can observe auroras in the polar regions, and also record the formation of magnetic storms.

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11. The distribution of solar winds cannot be called uniform. The distribution speed can reach its maximum when the wind passes over the so-called coronal holes. The slowest flow of streams can be recorded above streamers. Streams with different flow rates intersect with each other and with our planet.

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12. We have learned to obtain the greatest amount of information about the solar wind thanks to specially designed spacecraft. The list of such technological devices includes the well-known Ulysses satellite, thanks to which our knowledge of the solar wind has changed significantly. The chemical composition and speed of plasma flows were studied thanks to such a remarkable device. Additionally, with the help of the satellite, it was possible to determine the level of the magnetic field of our planet.
13. Another ACE satellite was launched into orbit back in 1997 near the L1 Lagrange point. It is at this point that solar and earth's gravity are in balance. On board this machine there are devices that continuously monitor the flow of solar winds so that people can explore information about directional plasma particles in real time, limited to the territory of the L1 sector.
14. Recently, the solar wind caused a geomagnetic storm on Earth. Intense flows emerged from the coronary hole in the solar atmosphere. Such holes can form in the luminary even in cases where there is a complete absence of active zones.
15. Today, a coronal hole has formed on the Sun.. Streams of plasma particles with a high distribution density reached the planet by mid-June, which caused the development of geomagnetic storms.