>What is the Sun made of?

Find out, what is the sun made of: a description of the structure and composition of the star, a list of chemical elements, the number and characteristics of layers with a photo, a diagram.

From Earth, the Sun looks like a smooth ball of fire, and before the discovery of sunspots by the comic ship Galileo, many astronomers thought it was perfectly shaped with no imperfections. Now we know that The sun is made up from several layers, like the Earth, each of which performs its own function. This structure of the Sun, like a massive oven, is the supplier of all the energy on Earth that is necessary for earthly life.

What elements does the sun consist of?

If you could take a star apart and compare the constituent elements, you would understand that the composition is 74% hydrogen and 24% helium. Also, the Sun is made up of 1% oxygen, and the remaining 1% is chemical elements periodic tables like chromium, calcium, neon, carbon, magnesium, sulfur, silicon, nickel, iron. Astronomers believe that an element heavier than helium is a metal.

How did all these elements of the Sun come about? The Big Bang produced hydrogen and helium. At the beginning of the formation of the Universe, the first element, hydrogen, appeared from elementary particles. Due to the high temperature and pressure, the conditions in the Universe were like in the core of a star. Later, hydrogen was fused into helium as long as there was a high temperature in the universe for the fusion reaction to take place. The existing proportions of hydrogen and helium, which are in the Universe now, were formed after the Big Bang and did not change.

The remaining elements of the Sun are created in other stars. The fusion of hydrogen into helium is constantly going on in the cores of stars. After producing all the oxygen in the core, they switch to nuclear fusion of heavier elements such as lithium, oxygen, helium. Many of the heavy metals that are in the Sun were also formed in other stars at the end of their lives.

The formation of the heaviest elements, gold and uranium, occurred when stars many times the size of our Sun detonated. In a fraction of a second of the formation of a black hole, the elements collided at high speed and the heaviest elements were formed. The explosion scattered these elements throughout the universe, where they helped form new stars.

Our Sun has collected elements created by the Big Bang, elements from dying stars, and particles from new detonations of stars.

What are the layers of the Sun?

At first glance, the Sun is just a ball of helium and hydrogen, but a closer look reveals that it is made up of different layers. When moving towards the core, the temperature and pressure increase, as a result of which layers were created, since hydrogen and helium have different characteristics under different conditions.

solar core

Let's start our movement through the layers from the core to the outer layer of the composition of the Sun. In the inner layer of the Sun - the core, the temperature and pressure are very high, contributing to the flow of nuclear fusion. The sun creates helium atoms from hydrogen, as a result of this reaction, light and heat are formed, which reach up to. It is generally accepted that the temperature on the Sun is about 13,600,000 degrees Kelvin, and the density of the core is 150 times higher than the density of water.

Scientists and astronomers believe that the core of the Sun reaches about 20% of the length of the solar radius. And inside the nucleus, high temperature and pressure help break hydrogen atoms into protons, neutrons, and electrons. The sun converts them into helium atoms, despite their free-floating state.

Such a reaction is called exothermic. During the course of this reaction, a large amount of heat is released, equal to 389 x 10 31 J. per second.

Radiation zone of the Sun

This zone originates at the boundary of the core (20% of the solar radius), and reaches a length of up to 70% of the solar radius. Inside this zone is the solar matter, which in its composition is quite dense and hot, therefore thermal radiation passes through it without losing heat.

Inside the solar core, a nuclear fusion reaction takes place - the creation of helium atoms as a result of the fusion of protons. As a result of this reaction, a large amount of gamma radiation occurs. In this process, photons of energy are emitted, then absorbed in the radiation zone and re-emitted by various particles.

The trajectory of a photon is called a "random walk". Instead of moving in a straight path to the surface of the Sun, the photon moves in a zigzag pattern. As a result, each photon needs approximately 200,000 years to overcome the radiation zone of the Sun. When passing from one particle to another particle, the photon loses energy. For the Earth, this is good, because we could only receive gamma radiation coming from the Sun. A photon that enters space needs 8 minutes to travel to Earth.

A large number of stars have radiation zones, and their size directly depends on the scale of the star. The smaller the star, the smaller the zones will be, most of which will be occupied by the convective zone. The smallest stars may lack radiation zones, and the convective zone will reach the distance to the core. For the largest stars, the situation is reversed, the radiation zone extends to the surface.

convective zone

The convective zone is outside the radiative zone, where the Sun's internal heat flows through columns of hot gas.

Almost all stars have such a zone. At our Sun, it extends from 70% of the radius of the Sun to the surface (photosphere). The gas in the depths of the star, at the very core, heats up and rises to the surface, like bubbles of wax in a lamp. Upon reaching the surface of the star, there is a loss of heat; when cooled, the gas sinks back to the center, for the renewal of thermal energy. As an example, you can bring a pot of boiling water over a fire.

The surface of the Sun is like loose soil. These irregularities are the columns of hot gas that carry heat to the surface of the Sun. Their width reaches 1000 km, and the dissipation time reaches 8-20 minutes.

Astronomers believe that stars of low mass, such as red dwarfs, have only a convective zone that extends to the core. They do not have a radiation zone, which cannot be said about the Sun.

Photosphere

The only layer of the Sun visible from the Earth is . Below this layer, the Sun becomes opaque, and astronomers use other methods to study the interior of our star. Surface temperatures as high as 6000 Kelvin glow yellow-white visible from Earth.

The Sun's atmosphere is located behind the photosphere. That part of the Sun that is visible during a solar eclipse is called.

The structure of the Sun in the diagram

NASA has specially developed for educational purposes a schematic representation of the structure and composition of the Sun, indicating the temperature for each layer:

• (Visible, IR and UV radiation) is visible radiation, infrared radiation and ultraviolet radiation. Visible radiation is the light that we see coming from the sun. Infrared radiation is the heat that we feel. Ultraviolet radiation is the radiation that gives us a tan. The sun produces these radiations simultaneously.
• (Photosphere 6000 K) - The photosphere is the upper layer of the Sun, its surface. A temperature of 6000 Kelvin is equal to 5700 degrees Celsius.
• Radio emissions - In addition to visible radiation, infrared radiation and ultraviolet radiation, the Sun sends out radio emissions, which astronomers have detected with a radio telescope. Depending on the number of sunspots, this emission increases and decreases.
• Coronal Hole - These are places on the Sun where the corona has a low plasma density, resulting in a darker and colder corona.
• 2100000 K (2100000 Kelvin) - The radiation zone of the Sun has this temperature.
• Convective zone / Turbulent convection (per. Convective zone / Turbulent convection) - These are places on the Sun where thermal energy the nucleus is transferred by convection. Plasma columns reach the surface, give off their heat, and rush down again to heat up again.
• Coronal loops (trans. Coronal loops) - loops consisting of plasma in the atmosphere of the Sun, moving along magnetic lines. They look like huge arches extending from the surface for tens of thousands of kilometers.
• Core (per. Core) is the solar heart, in which nuclear fusion takes place, using high temperature and pressure. All solar energy comes from the core.
• 14,500,000 K (per. 14,500,000 Kelvin) - The temperature of the solar core.
• Radiative Zone (trans. Radiation zone) - The layer of the Sun where energy is transferred using radiation. The photon overcomes the radiation zone beyond 200,000 and goes into outer space.
• Neutrinos (trans. Neutrino) are negligible mass particles emanating from the Sun as a result of a nuclear fusion reaction. Hundreds of thousands of neutrinos pass through the human body every second, but they do not bring us any harm, we do not feel them.
• Chromospheric Flare (trans. Chromospheric Flare) - The magnetic field of our star can twist, and then abruptly break in various forms. As a result of breaks in magnetic fields, powerful X-ray flares appear, emanating from the surface of the Sun.
• Magnetic Field Loop - The Sun's magnetic field is above the photosphere, and is visible as hot plasma moves along magnetic lines in the Sun's atmosphere.
• Spot - A sunspot (trans. Sunspots) - These are places on the surface of the Sun where magnetic fields pass through the surface of the Sun and the temperature is lower, often in a loop.
• Energetic particles (trans. Energetic particles) - They come from the surface of the Sun, as a result, the solar wind is created. In solar storms, their speed reaches the speed of light.
• X-rays (trans. X-rays) - rays invisible to the human eye, formed during flares on the Sun.
• Bright spots and short-lived magnetic regions (trans. Bright spots and short-lived magnetic regions) - Due to temperature differences, bright and dim spots appear on the surface of the Sun.

Photosphere - This is the visible surface of a star, spewing out the bulk of the optical radiation. The thickness of this layer is from 100 to 400 km, and the temperature is from 6600°K (inside) to 4400°K (at the outer edge). The dimensions of the Sun are determined precisely by the photosphere. The gas here is relatively rarefied, and its rotation speed is different depending on the area. In the equatorial region, one revolution occurs in 24 days, and in the region of the poles in 30 days.

This shell surrounds the photosphere, and its thickness is about 2000 km. The upper boundary of the chromosphere is characterized by constant hot ejecta - spicules. This part of the Sun can only be seen during a total solar eclipse. Then it appears in red tones.

This is the last shell. It is characterized by the presence of prominences and eruptions of energy. They splash out hundreds of thousands of kilometers, generating a solar wind.

The temperature of the corona is much higher than the surface of the Sun - 1,000,000 ° K - 2,000,000 ° K, and in some places from 8,000,000 ° K to 29,000,000 ° K. But you can only see the corona during a solar eclipse. The crown changes its shape. The changes depend on the cycle. At the peaks of the maximum, its shape is rounded, and at the minimum values ​​it is elongated along the equator.

sunny wind

The solar wind is a stream of ionized particles ejected from the Sun in all directions at a speed of about 400 km per second. The source of the solar wind is the solar corona. The temperature of the Sun's corona is so high that the gravitational force is not able to keep its matter near the surface, and part of this matter continuously flies into interplanetary space.

Although we understand the general reasons why the solar wind occurs, many of the details of this process are still not clear. In particular, at present it is not completely known where exactly the coronal gas is accelerated to such high velocities.

§ 43. sun

The sun is a star whose nuclear fusion reaction provides us with the energy we need to live.

The Sun is the closest star to the Earth. It gives light and heat, without which life on Earth would be impossible. Part of the solar energy falling on the Earth is absorbed and dissipated by the atmosphere. If this were not the case, then the radiation power received by each square meter of the Earth's surface from the sun's rays falling vertically would be about 1.4 kW / m 2. This value is called solar constant. Knowing the average distance from the Earth to the Sun and the solar constant, you can find the total radiation power of the Sun, called its luminosity and equal to about 4. 10 26 Tues.

The Sun is a huge hot ball, consisting mainly of hydrogen (70% of the mass of the Sun) and helium (28%), rotating around its axis (turn for 25-30 Earth days). The diameter of the Sun is 109 times that of the Earth. The apparent surface of the sun photosphere- the lowest and densest layer of the Sun's atmosphere, from which bó most of the energy it emits. The thickness of the photosphere is about 300 km, and the average temperature is 6000 K. Dark spots are often visible on the Sun ( sunspots), existing for several days, and sometimes months (Fig. 43 A). The layer of the Sun's atmosphere with a thickness of 12-15 thousand km, located above the photosphere, is called chromosphere. solar corona The outer layer of the Sun's atmosphere, extending to distances of several of its diameters. The brightness of the chromosphere and the solar corona is very small, and they can only be seen during a total solar eclipse (Fig. 43 b).

As we approach the center of the Sun, the temperature and pressure increase and near it are about 15× 10 6 K and 2.3 10 16 Pa, respectively. At such a high temperature, the solar matter becomes plasma- a gas consisting of atomic nuclei and electrons. The high temperature and pressure in core of the sun with a radius of about 1/3 of the radius of the Sun (Fig. 43 V) create conditions for reactions between nuclei, as a result of which nuclei are formed and huge energy is released.

Nuclear reactions in which lighter nuclei are converted into heavier ones are called thermonuclear(from lat. therme - heat), because they can only go at very high temperatures. The energy yield of a thermonuclear reaction can be several times greater than in fission of the same mass of uranium. The energy source of the Sun is thermonuclear reactions occurring in its core. High pressure The outer layers of the Sun not only creates the conditions for the occurrence of a thermonuclear reaction, but also keeps its core from exploding.

The energy of a thermonuclear reaction is released in the form of gamma radiation, which, leaving the core of the Sun, enters a spherical layer called radiant zone, with a thickness of about 1/3 of the radius of the Sun (Fig. 43 V). The substance located in the radiant zone absorbs gamma radiation coming from the nucleus and emits its own, but at a lower frequency. Therefore, as radiation quanta move from inside to outside, their energy and frequency decrease, and gamma radiation is gradually converted into ultraviolet, visible and infrared.

The outer shell of the sun is called convective zone, in which the mixing of the substance occurs ( convection), and the energy transfer is carried out by the movement of the substance itself (Fig. 43 V). A decrease in convection leads to a decrease in temperature by 1-2 thousand degrees and the appearance of a sunspot. At the same time, convection intensifies near the sunspot, and hotter matter is brought to the surface of the Sun, and in the chromosphere, prominences– emissions of matter at distances up to ½ of the radius of the Sun. Spotting is often accompanied solar flares- the bright glow of the chromosphere, X-rays and the flow of fast charged particles. It has been established that all these phenomena, called solar activity, occur the more often, the more sunspots. The number of sunspots on the Sun varies on average with a period of 11 years.

Review questions:

· What equal to the solar constant, and what is called the luminosity of the Sun?

· What is the internal structure of the Sun?

· Why does thermonuclear reaction take place only in the core of the Sun?

· List the phenomena of solar activity?

Rice. 43. ( A) are sunspots; ( b) is the solar corona during a solar eclipse; ( V) is the structure of the Sun ( 1 - core, 2 - radiant zone, 3 is the convective zone).

The internal structure of the Sun

© Vladimir Kalanov
Knowledge is power

What is visible on the Sun?

Everyone knows for sure that it is impossible to look at the Sun with the naked eye, and even more so through a telescope without special, very dark filters or other devices that weaken the light. Neglecting this prohibition, the observer runs the risk of severe eye burns. The easiest way to view the Sun is to project its image onto a white screen. With the help of even a small amateur telescope, you can get an enlarged image of the solar disk. What is seen in this image? First of all, the sharpness of the solar edge attracts attention. The sun is a gas ball that does not have a clear boundary, its density decreases gradually. Why, then, do we see it sharply defined? The fact is that almost all the visible radiation of the Sun comes from a very thin layer, which has a special name - the photosphere. (Greek "sphere of light"). The thickness of the photosphere does not exceed 300 km. It is this thin luminous layer that gives the observer the illusion that the Sun has a "surface".

The internal structure of the Sun

Photosphere

The atmosphere of the Sun begins 200-300 km deeper than the visible edge of the solar disk. These deepest layers of the atmosphere are called the photosphere. Since their thickness is no more than one three thousandth of the solar radius, the photosphere is sometimes conditionally called the surface of the Sun. The density of gases in the photosphere is approximately the same as in the Earth's stratosphere, and hundreds of times less than at the Earth's surface. The temperature of the photosphere decreases from 8000 K at a depth of 300 km to 4000 K in the uppermost layers. The temperature of that middle layer, the radiation of which we perceive, about 6000 K. Under such conditions, almost all gas molecules break up into individual atoms. Only in the uppermost layers of the photosphere are relatively few simple molecules and radicals of the type H, OH, CH preserved. A special role in the solar atmosphere is played by not found in terrestrial nature negative hydrogen ion, which is a proton with two electrons. This unusual compound occurs in the thin outer, "coldest" layer of the photosphere when negatively charged free electrons "stick" to neutral hydrogen atoms, which are supplied by easily ionizable atoms of calcium, sodium, magnesium, iron and other metals. When produced, negative hydrogen ions emit most of the visible light. The ions greedily absorb the same light, which is why the opacity of the atmosphere grows rapidly with depth. Therefore, the visible edge of the Sun seems to us very sharp.

In a telescope with a high magnification, you can observe the fine details of the photosphere: it all seems to be strewn with small bright grains - granules, separated by a network of narrow dark paths. Granulation is the result of the mixing of rising warmer gas streams and descending colder ones. The temperature difference between them in the outer layers is relatively small (200-300 K), but deeper, in the convective zone, it is greater, and mixing is much more intense. Convection in the outer layers of the Sun plays a huge role in determining the overall structure of the atmosphere. Ultimately, it is convection, as a result of a complex interaction with solar magnetic fields, that is the cause of all the diverse manifestations of solar activity. Magnetic fields are involved in all processes on the Sun. From time to time, concentrated magnetic fields arise in a small region of the solar atmosphere, several thousand times stronger than on Earth. Ionized plasma is a good conductor, it cannot move across the lines of magnetic induction of a strong magnetic field. Therefore, in such places, the mixing and rise of hot gases from below is inhibited, and a dark area appears - a sunspot. Against the background of the dazzling photosphere, it seems completely black, although in reality its brightness is only ten times weaker. Over time, the size and shape of the spots change greatly. Having arisen in the form of a barely noticeable point - a pore, the spot gradually increases its size to several tens of thousands of kilometers. Large spots, as a rule, consist of a dark part (core) and a less dark part - penumbra, the structure of which gives the spot the appearance of a vortex. Spots are surrounded by brighter areas of the photosphere, called faculae or torch fields. The photosphere gradually passes into more rarefied outer layers of the solar atmosphere - the chromosphere and corona.

Chromosphere

Above the photosphere is the chromosphere, an inhomogeneous layer whose temperature ranges from 6,000 to 20,000 K. The chromosphere (Greek for "color sphere") is so named for its reddish-violet color. It is visible during total solar eclipses as a ragged bright ring around the black disk of the Moon, which has just eclipsed the Sun. The chromosphere is very heterogeneous and consists mainly of elongated elongated tongues (spicules), giving it the appearance of burning grass. The temperature of these chromospheric jets is two to three times higher than in the photosphere, and the density is hundreds of thousands of times lower. The total length of the chromosphere is 10-15 thousand kilometers. The increase in temperature in the chromosphere is explained by the propagation of waves and magnetic fields penetrating into it from the convective zone. The substance heats up in much the same way as if it were in a giant microwave oven. The speeds of thermal motions of particles increase, collisions between them become more frequent, and atoms lose their outer electrons: matter becomes a hot ionized plasma. These same physical processes support and unusually high temperature the outermost layers of the solar atmosphere, which are located above the chromosphere.

Often during eclipses (and with the help of special spectral instruments - even without waiting for eclipses) over the surface of the Sun, one can observe bizarrely shaped "fountains", "clouds", "funnel", "bushes", "arches" and other brightly luminous formations from the chromospheric substances. They are stationary or slowly changing, surrounded by smooth curved jets that flow into or out of the chromosphere, rising tens and hundreds of thousands of kilometers. These are the most grandiose formations of the solar atmosphere -. When observed in the red spectral line emitted by hydrogen atoms, they appear against the background of the solar disk as dark, long and curved filaments. Prominences have approximately the same density and temperature as the chromosphere. But they are above it and are surrounded by higher, highly rarefied upper layers of the solar atmosphere. Prominences do not fall into the chromosphere because their substance is supported by the magnetic fields of active regions of the Sun. For the first time, the spectrum of a prominence outside an eclipse was observed by the French astronomer Pierre Jansen and his English colleague Joseph Lockyer in 1868. The spectroscope slit is positioned so that it crosses the edge of the Sun, and if there is a prominence near it, then you can notice the spectrum of its radiation. By pointing the slit at different parts of the prominence or chromosphere, one can study them in parts. The spectrum of prominences, like that of the chromosphere, consists of bright lines, mainly hydrogen, helium, and calcium. The emission lines of other chemical elements are also present, but they are much weaker. Some prominences, having spent a long time without noticeable changes, suddenly explode, as it were, and their substance is ejected into interplanetary space at a speed of hundreds of kilometers per second. The appearance of the chromosphere also changes frequently, which indicates the continuous movement of its constituent gases. Sometimes something similar to explosions occurs in very small regions of the Sun's atmosphere. These are the so-called chromospheric flares. They usually last several tens of minutes. During flares in the spectral lines of hydrogen, helium, ionized calcium, and some other elements, the luminosity of an individual section of the chromosphere suddenly increases tenfold. The ultraviolet and X-ray radiation increases especially strongly: sometimes its power is several times higher than the total power of the Sun's radiation in this short-wavelength region of the spectrum before the flare. Spots, torches, prominences, chromospheric flares are all manifestations of solar activity. With an increase in activity, the number of these formations on the Sun becomes greater.

Atmosphere of the Sun

Layer name	Height of the upper boundary of the layer, km	Density, kg / m 3	Temperature, K
Photosphere
Chromosphere
	Several tens of solar radii

Sunspots (dark formations on the solar disk, due to the fact that their temperature is ~ 1500 K lower than the temperature of the photosphere) consist of a dark oval - the shadow of a spot, surrounded by a lighter fibrous penumbra. The smallest sunspots (pores) have diameters of ~1000 km, and the diameters of the largest sunspots observed exceeded 100,000 km. Small spots often exist for less than 2 days, developed 10-20 days, the largest can be observed up to 100 days.

Chromospheric spicules (isolated gas columns) have a diameter of ~1000 km, a height of up to ~8000 km, a rise and fall speed of ~20 km/s, a temperature of ~15,000 K, and a lifetime of several minutes.

Prominences (comparatively cold dense clouds in the corona) extend in length up to 1/3 of the radius of the Sun. The most common are "calm" prominences with a lifetime of up to 1 year, a length of ~200 thousand km, a thickness of ~10 thousand km, and a height of ~30 thousand km. With velocities of 100-1000 km/s, fast eruptive prominences are usually ejected upwards after flares.

During a total solar eclipse, the brightness of the sky around the Sun is 1.6 10 -9 of the average brightness of the Sun.

The brightness of the Moon during a total solar eclipse in the light reflected from the Earth is 1.1 10 -10 of the average brightness of the Sun.

Photosphere

The photosphere (the layer that emits light) forms the visible surface of the Sun. Its thickness corresponds to an optical thickness of approximately 2/3 units. In absolute terms, the photosphere reaches a thickness, according to various estimates, from 100 to 400 km. The main part of the optical (visible) radiation of the Sun comes from the photosphere, while the radiation from deeper layers no longer reaches us. The temperature decreases from 6600 K to 4400 K as it approaches the outer edge of the photosphere. The effective temperature of the photosphere as a whole is 5778 K. It can be calculated according to the Stefan-Boltzmann law, according to which the radiation power of an absolutely black body is directly proportional to the fourth power of body temperature. Hydrogen under such conditions remains almost completely in a neutral state. The photosphere forms the visible surface of the Sun, which determines the size of the Sun, the distance from the Sun, etc. Since the gas in the photosphere is relatively rarefied, its rotation speed is much less than the rotation speed solids. At the same time, gas in the equatorial and polar regions moves unevenly - at the equator it makes a revolution in 24 days, at the poles - in 30 days.

Chromosphere

The chromosphere is the outer shell of the Sun with a thickness of about 2000 km, surrounding the photosphere. The origin of the name of this part of the solar atmosphere is associated with its reddish color, caused by the fact that the red H-alpha hydrogen emission line from the Balmer series dominates in the visible spectrum of the chromosphere. The upper boundary of the chromosphere does not have a pronounced smooth surface; hot ejections, called spicules, constantly occur from it. The number of spicules observed simultaneously averages 60-70 thousand. Because of this, in late XIX century, the Italian astronomer Secchi, observing the chromosphere through a telescope, compared it with burning prairies. The temperature of the chromosphere increases with height from 4,000 to 20,000 K (the temperature range above 10,000 K is relatively small).

The density of the chromosphere is low, so the brightness is insufficient for observation under normal conditions. But during a total solar eclipse, when the Moon covers the bright photosphere, the chromosphere located above it becomes visible and glows red. It can also be observed at any time using special narrow-band optical filters. In addition to the already mentioned H-alpha line with a wavelength of 656.3 nm, the filter can also be tuned to the Ca II K (393.4 nm) and Ca II H (396.8 nm) lines. The main chromospheric structures that are visible in these lines are:

· a chromospheric grid covering the entire surface of the Sun and consisting of lines surrounding supergranulation cells up to 30,000 km across;

floccules - light cloud-like formations, most often confined to areas with strong magnetic fields - active areas, often surround sunspots;

fibers and fibers (fibrils) - dark lines of various widths and lengths, like flocculi, are often found in active areas.

Crown

The corona is the last outer shell of the Sun. The corona is primarily composed of prominences and energetic eruptions, erupting and erupting several hundred thousand and even more than a million kilometers into space, forming the solar wind. The average coronal temperature is from 1 to 2 million K, and the maximum, in some areas, is from 8 to 20 million K. Despite such a high temperature, it is visible to the naked eye only during a total solar eclipse, since the density of matter in the corona is low , and therefore its brightness is also small. The unusually intense heating of this layer is apparently caused by the effect of magnetic reconnection and the action of shock waves (see Coronal heating problem). The shape of the corona changes depending on the phase of the solar activity cycle: during periods of maximum activity, it has a rounded shape, and at minimum, it is elongated along the solar equator. Since the temperature of the corona is very high, it radiates intensely in the ultraviolet and X-ray ranges. These radiations do not pass through earth's atmosphere, but recently it has become possible to study them with the help of spacecraft. Radiation in different regions of the corona occurs unevenly. There are hot active and quiet regions, as well as coronal holes with a relatively low temperature of 600,000 K, from which magnetic field lines emerge into space. This ("open") magnetic configuration allows particles to leave the Sun unhindered, so the solar wind is emitted primarily from coronal holes.

The visible spectrum of the solar corona consists of three different components, called the L, K and F components (or, respectively, the L-corona, K-corona and F-corona; another name for the L-component is the E-corona. The K-component is continuous spectrum of the corona. Against its background, the emission L-component is visible up to a height of 9-10 "from the visible edge of the Sun. Starting from a height of about 3" (the angular diameter of the Sun is about 30 ") and higher, a Fraunhofer spectrum is visible, the same as the spectrum of the photosphere. It constitutes the F component of the solar corona.At a height of 20', the F component dominates the spectrum of the corona.A height of 9-10' is taken as the boundary separating the inner corona from the outer.The radiation of the Sun with a wavelength of less than 20 nm comes entirely from the corona.This means that, for example, in common images of the Sun at wavelengths of 17.1 nm (171 Å), 19.3 nm (193 Å), 19.5 nm (195 Å), only the solar corona with its elements is visible, and the chromosphere and the photosphere are not visible.Two coronal holes, almost always existing near the northern and southern poles of the Sun, as well as others temporarily appearing on its visible surface, practically do not emit X-rays at all.

sunny wind

From the outer part of the solar corona, the solar wind flows out - a stream of ionized particles (mainly protons, electrons and α-particles), propagating with a gradual decrease in its density, to the boundaries of the heliosphere. The solar wind is divided into two components - the slow solar wind and the fast solar wind. The slow solar wind has a speed of about 400 km/s and a temperature of 1.4–1.6·10 6 K and closely corresponds to the corona in composition. The fast solar wind has a speed of about 750 km/s, a temperature of 8·10 5 K, and is similar in composition to the substance of the photosphere. The slow solar wind is twice as dense and less constant than the fast one. The slow solar wind has a more complex structure with regions of turbulence.

On average, the Sun radiates with the wind about 1.3·10 36 particles per second. Consequently, the total loss of mass by the Sun (for this type of radiation) is 2-3·10 −14 solar masses per year. The loss in 150 million years is equivalent to the mass of the earth. Many natural phenomena on Earth are associated with disturbances in the solar wind, including geomagnetic storms and auroras.

The first direct measurements of the characteristics of the solar wind were carried out in January 1959 by the Soviet station Luna-1. Observations were carried out using a scintillation counter and a gas ionization detector. Three years later, the same measurements were carried out by American scientists using the Mariner-2 station. In the late 1990s, using the Coronal Ultraviolet Spectrometer (Eng.Ultraviolet Coronal Spectrometer ( UVCS) ) on board the SOHO satellite, observations were made of the regions of fast solar wind occurrence at the solar poles.