Milky Way - Shasha Galaxy
Solar atmosphere - photosphere
Photosphere
- the atmosphere of the Sun begins 200-300 km deeper than the visible edge of the solar edge. 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 at the most upper layers. The temperature of the middle layer, the radiation of which we perceive, is about 6000 K. Under such conditions, almost all gas molecules decay into individual atoms. Only in the uppermost layers of the photosphere are relatively few simple molecules and radicals such as H 2 , OH, CH preserved.
A special role in the solar atmosphere is played by the negative hydrogen ion, which is not found in terrestrial nature, 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 eagerly absorb the same light, which is why the opacity of the atmosphere rapidly increases with depth. Therefore, the visible edge of the Sun seems to us very sharp.
Almost all of our knowledge about the Sun is based on the study of its spectrum - a narrow multi-colored strip that has the same nature as a rainbow. For the first time, placing a prism in the path of a sunbeam, Newton received such a strip and exclaimed: "Spectrum!"(lat. spectrum - "vision"). Later, dark lines were noticed in the spectrum of the Sun and considered to be the boundaries of colors.
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 warmer gas streams rising up and colder ones sinking. 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 region appears - a sunspot. Against the background of the dazzling photosphere, it seems completely black, although in reality its brightness is only ten 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.
Solar atmosphere - chromosphere
Chromosphere
(Greek "sphere of color") is so named for its reddish-purple 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 happening 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: the substance becomes a hot ionized plasma. These same physical processes also maintain the unusually high temperature of 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) above 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 - prominences. 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 a prominence is located 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 others 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, indicating 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 (the most powerful explosion-like processes can last only a few minutes, but during this time energy is released, which sometimes reaches 10 25 J). 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 solar radiation power 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.
Solar atmosphere - corona
Crown
Unlike the photosphere and chromosphere, the most outer part The Sun's atmosphere is enormous: it extends for millions of kilometers, which corresponds to several solar radii, and its weak extension goes even further.
The density of matter in the solar corona decreases with height much more slowly than the density of air in the Earth's atmosphere. The decrease in air density as it rises is determined by the gravity of the Earth. On the surface of the Sun, gravity is much stronger, and, it would seem, its atmosphere should not be high. In fact, it is unusually extensive. Therefore, there are some forces acting against the attraction of the Sun. These forces are associated with the huge speeds of movement of atoms and electrons in the corona, heated to a temperature of 1-2 million degrees!
The corona is best observed during the total phase of a solar eclipse. True, in the few minutes that it lasts, it is very difficult to sketch not only individual details, but even general form crowns. The eye of the observer is just beginning to get used to the sudden twilight, and a bright ray of the Sun that has appeared from behind the edge of the Moon is already announcing the end of the eclipse. Therefore, often the sketches of the corona, made by experienced observers during the same eclipse, were very different. It was not even possible to accurately determine its color.
The invention of photography gave astronomers an objective and documentary method of research. However, getting a good picture of the corona is also not easy. The fact is that the part closest to the Sun, the so-called inner corona, is relatively bright, while the far-reaching outer corona appears to be a very pale glow. Therefore, if the outer corona is clearly visible in the photographs, then the inner one turns out to be overexposed, and in the photographs, where the details of the inner corona are visible, the outer one is completely invisible. To overcome this difficulty, during an eclipse, they usually try to get several pictures of the corona at once - with long and short shutter speeds. Or the crown is photographed by placing a special "radial" filter in front of the photographic plate, which weakens the annular zones of bright internal parts crowns. In such images, its structure can be traced to distances of many solar radii.
Already the first successful photographs made it possible to detect in the crown a large number of details: coronal rays, all kinds of "arcs", "helmets" and other complex formations clearly associated with active regions.
The main feature of the crown is the radiant structure. Coronal rays have a wide variety of shapes: sometimes they are short, sometimes long, sometimes the rays are straight, and sometimes they are strongly curved. Back in 1897, the Pulkovo astronomer Alexei Pavlovich Gansky discovered that the general view solar corona changes periodically. It turned out that this is due to the 11-year cycle of solar activity.
With an 11-year period, both the overall brightness and the shape of the solar corona change. During the epoch of sunspot maximum, it has a relatively rounded shape. Direct rays of the corona and directed along the radius of the Sun are observed both near the solar equator and in the polar regions. When there are few sunspots, coronal rays form only at equatorial and middle latitudes. The shape of the crown becomes elongated. Characteristic short rays appear at the poles, the so-called polar brushes. In this case, the overall brightness of the corona decreases. This interesting feature corona, apparently, is associated with the gradual movement during the 11-year cycle of the zone of predominant formation of spots. After the minimum, spots begin to appear on both sides of the equator at latitudes of 30-40°. Then the spot formation zone gradually descends towards the equator.
Careful studies have made it possible to establish that there is a certain relationship between the structure of the corona and individual formations in the solar atmosphere. For example, bright and direct coronal rays are usually observed above sunspots and faculae. Neighboring beams bend in their direction. At the base of the coronal rays, the brightness of the chromosphere increases. Such an area is usually called excited. It is hotter and denser than neighboring, unexcited areas. Bright complex formations are observed above the spots in the corona. Prominences are also often surrounded by shells of coronal matter.
The corona turned out to be a unique natural laboratory in which matter can be observed in the most unusual and unattainable conditions on Earth.
At the turn of the 19th-20th centuries, when plasma physics actually did not yet exist, the observed features of the corona seemed to be an inexplicable mystery. So, in color, the crown is surprisingly similar to the Sun, as if its light is reflected by a mirror. At the same time, however, in the inner corona, the characteristic solar spectrum Fraunhofer lines. They reappear far from the edge of the Sun, in the outer corona, but already very weak. In addition, the light of the corona is polarized: the planes in which the light waves oscillate are located mainly tangential to the solar disk. With distance from the Sun, the proportion of polarized rays first increases (almost to 50%), and then decreases. Finally, bright emission lines appear in the spectrum of the corona, which almost until the middle of the 20th century. could not be identified with any of the known chemical elements.
It turned out that main reason all these features of the crown - heat highly rarefied gas. At temperatures above 1 million degrees, the average velocities of hydrogen atoms exceed 100 km / s, and for free electrons they are 40 times more. At such speeds, despite the strong rarefaction of matter (only 100 million particles per cubic cm, which is 100 billion times rarer than air on Earth!), Collisions of atoms, especially with electrons, are relatively frequent. The forces of electron impacts are so great that the atoms of light elements are almost completely deprived of all their electrons and only "bare" atomic nuclei remain from them. Heavier elements retain the deepest electron shells, passing into a state of high degree of ionization.
So coronal gas is a highly ionized plasma; it consists of many positively charged ions of various chemical elements and a slightly larger number of free electrons arising from the ionization of hydrogen atoms (one electron each), helium (two electrons each) and heavier atoms. Since mobile electrons play the main role in such a gas, it is often called an electron gas, although this implies the presence of such a quantity of positive ions that would completely ensure the neutrality of the plasma as a whole.
White color corona is due to the scattering of ordinary sunlight on free electrons. They do not invest their energy during scattering: oscillating in time with the light wave, they only change the direction of the scattered light, while polarizing it. The mysterious bright lines in the spectrum are generated by the unusual radiation of highly ionized atoms of iron, argon, nickel, calcium and other elements, which occurs only under conditions of strong rarefaction. Finally, the absorption lines in the outer corona are caused by scattering by dust particles that are constantly present in the interstellar medium. And the absence of a line in the inner corona is due to the fact that when scattered by very fast moving electrons, all light quanta experience such significant frequency changes that even strong Fraunhofer lines of the solar spectrum are completely "washed out".
So, the corona of the Sun is the outermost part of its atmosphere, the most rarefied and the hottest. We add that it is also the closest to us: it turns out that it extends far from the Sun in the form of a stream of plasma constantly moving from it - the solar wind. Near the Earth, its speed averages 400-500 km/s, and sometimes reaches almost 1000 km/s. Spreading far beyond the orbits of Jupiter and Saturn, the solar wind forms a gigantic heliosphere bordering on an even more rarefied interstellar medium.
In fact, we live surrounded by the solar corona, although protected from its penetrating radiation by a reliable barrier in the form of the earth's magnetic field. Through the corona, solar activity affects many processes occurring on Earth (geophysical phenomena).
How the sun affects the earth
The sun illuminates and warms our planet; without this, life on it would be impossible not only for humans, but even for microorganisms. The sun is the main (although not the only) engine of the processes occurring on Earth. But not only heat and light is received by the Earth from the Sun. Various types of solar radiation and particle flows have a constant impact on her life.
The Sun sends electromagnetic waves to the Earth in all areas of the spectrum - from many kilometers of radio waves to gamma rays. The surroundings of the Earth are also reached by charged particles of different energies - both high and low and medium. Finally, the Sun emits a powerful stream of elementary particles - neutrinos. However, the impact of the latter on terrestrial processes is negligibly small: for these particles Earth transparent, and they fly through it freely. Only a very small part of charged particles from interplanetary space enters the Earth's atmosphere (the rest is deflected or delayed by the geomagnetic field). But their energy is enough to cause auroras and perturbations of the magnetic field of our planet.
The electromagnetic disturbance is subjected to strict selection in the earth's atmosphere. It is transparent only to visible light and the nearest ultraviolet and infrared radiation, as well as to radio waves in a relatively narrow range (from centimeter to meter). All other radiation is either reflected or absorbed by the atmosphere, heating and ionizing its upper layers.
X-ray absorption and hard ultraviolet rays starts at exhausts of 300-350 km; at the same heights, the longest radio waves coming from space are reflected. With strong bursts of solar X-rays from chromospheric flares, X-ray quanta penetrate to altitudes of 80-100 km from the Earth's surface, ionize the atmosphere and cause disruption of communication at short wavelengths.
 |
| Dark, ominous areas on the left side of the solar disk are the so-called coronal holes. These regions, located above the surface, where the lines of force of the solar magnetic field go into interplanetary space, are characterized by reduced pressure. Coronal holes have been intensively studied from satellites since the 1960s in ultraviolet and X-ray light. It is known that they are sources of intense solar wind, which consists of atoms and electrons flying away from the Sun along open magnetic field lines. |
| OUR SUN |
Soft (long-wave) ultraviolet radiation is able to penetrate even deeper, it is absorbed at a height of 30-35 km. Here, ultraviolet quanta are broken into atoms of oxygen molecules, followed by the formation of ozone. This creates an "ozone screen" that is not transparent to ultraviolet, protecting life on Earth from fatal rays. The unabsorbed part of the longest wavelength ultraviolet radiation reaches the earth's surface. It is these rays that cause sunburn in people.
Radiation in the visible range is weakly absorbed. However, it is dissipated by the atmosphere even in the absence of clouds, and part of it returns to interplanetary space. Clouds, consisting of water droplets and solid particles, greatly enhance the reflection of solar radiation. As a result, on average, about half of the light incident on the boundary of the Earth's atmosphere reaches the surface of the planet.
The amount of solar energy falling on a surface of 1 square meter, deployed perpendicularly sunbeams at the edge of the earth's atmosphere is called the solar constant. It is very difficult to measure it from the Earth, and therefore the values found before space research, were very approximate. Small fluctuations (if they really existed) obviously "drowned" in the inaccuracies of measurements. Only the implementation of a special space program to determine the solar constant made it possible to find its reliable value. According to the latest data, it is 1370 W / m 2 with an accuracy of 0.5%. Fluctuations exceeding 0.2% were not detected during the measurements.
On Earth, radiation is absorbed by land and oceans. The heated earth's surface, in turn, radiates in the long-wave infrared region. For such radiation, the nitrogen and oxygen of the atmosphere are transparent. But it is greedily absorbed by water vapor and carbon dioxide. Thanks to these small components, the air shell retains heat. This is what the greenhouse effect atmosphere. In general, there is a balance between the arrival of solar energy on Earth and its losses on the planet: how much comes in, how much is spent. Otherwise, the temperature earth's surface together with the atmosphere would either constantly rise or fall.
- all phenomena of solar activity are associated with the release of magnetic fields to the surface of the Sun. Already the first measurements of the Zeeman effect, carried out at the beginning of the 20th century, showed that fields in spots are characterized by an intensity of the order of several thousand oersteds, and such fields are realized in regions with a diameter of 20,000 km. Modern appliances for measuring fields on the Sun make it possible not only to measure the magnitude of the field with an accuracy of 1 Oe, but also to judge the angles of inclination of the magnetic field strength vector. It was found, for example, that torches are regions with fields of 5-300 Oe. In the shadow of sunspots, the fields reach 1000-4500 Oe. parallel to the solar surface. The field is concentrated in separate bundles.
 |
| The sun is very restless. This false color image shows an active region located on the edge of the Sun's disk. Hot plasma escapes from the solar photosphere and moves along the magnetic field lines. Very hot regions are marked in red, indicating that hotter material propagates through some loops of the magnetic field than other loops. The magnetic field loops are very large, so that the Earth can easily fit inside them. |
 |
| OUR SUN |
The field averaged over the solar surface is of the order of 1 Oe; it apparently consists of individual cells with 10 Oe at their boundaries. Such a field is observed near the poles of the Sun, while at low latitudes it is often perturbed by the strong fields of active regions. These strong local fields perturb not only the photosphere, but also penetrate into the outer layers. In the chromosphere above the shadow of spots, their magnitude can reach 1000 Oe, over the penumbra and faculae 100 Oe. Indirect data say that the fields in the corona above the active region are 10-0.1 Oe, the active region (or center of activity) is identified with a place of increased magnetic field strength. The lower base of the active region - faculae and spots - is located in the photosphere. The upper part appears as a chromospheric torch (flocculus), and in the corona - as coronal condensation.
Most often, active regions are characterized by two poles of opposite polarity - the so-called. bipolar centers, although there are both multipolar and unipolar regions. Poles of opposite polarity are connected by a system of arches up to 30,000 km long and up to 5,000 km high. The tops of the arches slowly rise, and near the poles the gas flows down towards the photosphere.
The development of the active region in time is peculiar. With the strengthening of the magnetic field in the photosphere, a torch appears, gradually increasing its area and brightness. After about a day, several dark dots appear in it - pores, which then develop into sunspots. The tenth - eleventh days of the life of the region are characterized by the most violent processes in the chromosphere and corona. In this case, the size of large groups of spots reaches 20 heliographic degrees in longitude and 10 in latitude, or 2400 km X 12,000 km. After 1-3 months, the spots gradually disappear, a giant prominence hangs over the area. After six months or a year, this area disappears.
For an average spot with a field of 3000 Oe, the magnetic energy is at least 10 times greater than the kinetic energy. energy of convective motions. But in a convective cell, there is necessarily a horizontal displacement perpendicular to the direction of the field. The field prevents horizontal movement, as a result of which the convection in the spots is significantly weakened. Difficulty convection leads to less energy in the area of spots, because the energy in the deep layers is transferred by convective motions. This is probably the reason for the lower temperature and the "blackness" of the spots.
The granules observed in the shadow of spots (with sizes up to 300 km and an average lifetime of 15–30 min) indicate the presence of strongly modified convection. It consists here in individual elements hot gas erupt in spots along the field to photospheric heights. There they expand, compressing the surrounding gas along with the field. Dense gas descends, the motions of the gas are reminiscent of moving up and down in closely spaced pipes with little change in cross section (i.e., little deformation of the field lines). In many other cases - when gas moves in prominences, in coronal loops, the trajectories of gas movement also coincide with the course of field lines.
The degree of influence of the field on the structure of the outer atmosphere depends both on the magnitude of the magnetic flux emerging on the surface (1017-1022 μs) and on how much it changes with height and time.
|
The photosphere - that layer of the solar atmosphere that we see through a telescope and perceive with the eye as a surface, has a temperature of about 5,800 C. During the period of minimum solar activity, the surface of the photosphere is relatively calm. All the whirlwinds of thermonuclear reactions that give the star its energy are raging deep inside. But with the beginning of a new cycle, the energy of all these internal processes begins to break out. |
sun activity photosphere wind
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 it. 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.
Chromosphere (from other Greek chspmb - color, utsbYasb - ball, sphere) - 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 crown 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 1,000,000 to 2,000,000 K, and the maximum, in some areas, is from 8,000,000 to 20,000,000 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 low. The unusually intense heating of this layer is apparently caused by the effect of magnetic attachment and the action of shock waves. 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 the earth's atmosphere, but in recent times it became 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.
sunny wind. From the outer part of the solar corona, the solar wind flows out - a stream of ionized particles (mainly protons, electrons and 6-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 its composition closely corresponds to the corona. 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.
To get to know internal structure Sun, let's now make an imaginary journey from the center of the star to its surface. But how are we going to determine the temperature and density of the solar globe at different depths? How can we find out what processes are taking place inside the Sun?
It turns out that most of the physical parameters of stars (our Sun is also a star!) are not measured, but calculated theoretically using computers. Only some General characteristics star, such as its mass, radius, and physical conditions, prevailing on its surface: temperature, extent and density of the atmosphere, and the like. The chemical composition of a star (in particular, the Sun) is determined by the spectral path. And on the basis of these data, a theoretical astrophysicist will create a mathematical model of the Sun. If such a model corresponds to the results of observations, then it can be considered a fairly good approximation to reality. And we, relying on such a model, will try to imagine all the exotic depths of the great luminary.
The central part of the Sun is called its core. Matter inside the solar core is extremely compressed. Its radius is approximately 1/4 of the Sun's radius, and its volume is 1/45 (a little over 2%) of the Sun's total volume. Nevertheless, almost half of the luminary is packed in the core solar mass. This became possible due to the very high degree of ionization of the solar matter. The conditions there are exactly what are needed for the operation of a thermonuclear reactor. The Core is a giant controlled power station where solar energy is born.
Having moved from the center of the Sun by about 1/4 of its radius, we enter the so-called radiation energy transfer zone. This most extensive inner region of the Sun can be imagined like the walls of a nuclear boiler, through which solar energy slowly seeps out. But the closer to the surface of the Sun, the lower the temperature and pressure. As a result, vortex mixing of the substance occurs and energy transfer occurs mainly by the substance itself. This method of energy transfer is called convection, and the subsurface layer of the Sun, where it occurs, is called the convective zone. Solar researchers believe that its role in the physics of solar processes is exceptionally great. After all, it is here that various movements of the solar substance and magnetic fields originate.
Finally we are at the visible surface of the Sun. Since our Sun is a star, a hot plasma ball, it, unlike the Earth, the Moon, Mars and similar planets, cannot have a real surface, understood in the full sense of the word. And if we are talking about the surface of the Sun, then this concept is conditional.
The visible luminous surface of the Sun, located directly above the convective zone, is called the photosphere, which in Greek means "sphere of light."
The photosphere is a 300 km layer. This is where the sun's rays come from. And when we look at the Sun from the Earth, the photosphere is just the layer that permeates our vision. The radiation from the deeper layers no longer reaches us, and it is impossible to see them.
The temperature in the photosphere increases with depth and is estimated on average at 5800 K.
The main part of the optical (visible) radiation of the Sun comes from the photosphere. Here, the average density of the gas is less than 1/1000 of the density of the air we breathe, and the temperature decreases to 4800 K as we approach the outer edge of the photosphere. Hydrogen under such conditions remains almost completely in a neutral state.
Astrophysicists take the base of the photosphere for the surface of the great luminary. They consider the photosphere itself to be the lowest (inner) layer of the solar atmosphere. Above it are two more layers that form the outer layers of the solar atmosphere, the chromosphere and the corona. And although there are no sharp boundaries between these three layers, let's get acquainted with their main distinguishing features.
The yellow-white light of the photosphere has a continuous spectrum, that is, it looks like a continuous rainbow strip with a gradual transition of colors from red to purple. But in the lower layers of the rarefied chromosphere, in the region of the so-called temperature minimum, where the temperature drops to 4200 K, sunlight undergoes absorption, due to which narrow absorption lines form in the spectrum of the Sun. They are called Fraunhofer lines, after the German optician Josef Frau and Gopher, who carefully measured the wavelengths of 754 lines in 1816.
To date, more than 26,000 dark lines of varying intensity have been recorded in the spectrum of the Sun, arising from the absorption of light by "cold" atoms. And since each chemical element has its own characteristic set of absorption lines, this makes it possible to determine its presence in the outer layers of the solar atmosphere.
The chemical composition of the Sun's atmosphere is similar to that of most stars formed over the past few billion years (they are called second-generation stars). Compared to the old celestial bodies (stars of the first generation), they contain ten times more heavy elements, that is, elements that are heavier than helium. Astrophysicists believe that heavy elements first appeared as a result of nuclear reactions occurring during the explosions of stars, and possibly even during the explosions of galaxies. During the formation of the Sun, the interstellar medium was already quite well enriched in heavy elements (the Sun itself does not yet produce elements heavier than helium). But our Earth and other planets apparently condensed from the same gas and dust cloud as the Sun. Therefore, it is possible that by studying chemical composition of our daylight, we are also studying the composition of the primary protoplanetary matter.
Since the temperature in the solar atmosphere varies with altitude, absorption lines at different levels are produced by atoms of different chemical elements. This allows you to study the various atmospheric layers of the great star and determine their length.
Above the photosphere is a more rarefied syllable! atmosphere of the Sun, which is called the chromosphere, which means "colored sphere". Its brightness is many times less than the brightness of the photosphere, so the chromosphere is visible only during short minutes of total solar eclipses, like a pink ring around the dark disk of the Moon. The reddish color of the chromosphere is due to hydrogen radiation. This gas has the most intense spectral line, Ha, in the red region of the spectrum, and there is a particularly large amount of hydrogen in the chromosphere.
The spectra obtained during solar eclipses show that the red line of hydrogen disappears at an altitude of approximately 12,000 km above the photosphere, while ionized calcium limes cease to be visible at an altitude of 14,000 km. This height is considered as the upper boundary of the chromosphere. As the temperature rises, the temperature rises, reaching 50,000 K in the upper layers of the chromosphere. As the temperature rises, the ionization of hydrogen, and then helium, intensifies.
The increase in temperature in the chromosphere is quite understandable. As is known, the density of the solar atmosphere rapidly decreases with height, and a rarefied medium radiates less energy than a dense one. Therefore, the energy coming from the Sun heats up the upper chromosphere and the corona lying above it.
At present, heliophysicists using special instruments observe the chromosphere not only during solar eclipses, but also on any clear day. During total solar eclipses, you can see the outermost shell of the solar atmosphere - the corona - a delicate pearl-silvery glow that extends around the eclipsed Sun. The total brightness of the corona is about one millionth of the light of the Sun, or half of the light of the full moon.
The solar corona is a highly rarefied plasma with a temperature close to 2 million K. The density of coronal matter is hundreds of billions of times less than the density of air near the Earth's surface. Under such conditions, the atoms of chemical elements cannot be in a neutral state: their speed is so high that in mutual collisions they lose almost all of their electrons and are repeatedly ionized. This is why the solar corona is made up primarily of protons (the nuclei of hydrogen atoms), helium nuclei, and free electrons.
The exceptionally high temperature of the corona leads to the fact that its substance becomes a powerful source of ultraviolet and X-ray radiation. For observations in these ranges of the electromagnetic spectrum, as is known, special ultraviolet and X-ray telescopes installed on spacecraft and orbiting scientific stations are used.
With the help of radio methods (the solar corona intensely emits decimeter and meter radio waves), coronal rays are "seen" up to distances of 30 solar radii from the edge of the solar disk. With distance from the Sun, the density of the corona decreases very slowly, and its uppermost layer flows out into outer space. This is how the solar wind is formed.
Only due to the volatilization of corpuscles, the mass of the Sun decreases every second by at least 400 thousand tons.
The solar wind blows over the entire space of our planetary system. By this time, the initial speed reaches more than 1000 km/s, but then it slowly decreases. At the Earth's orbit average speed winds around 400 km/s. Om sweeps on its way all the gases emitted by planets and comets, the smallest meteor dust particles and even particles of galactic cosmic rays of low energies, taking all this "garbage" to the outskirts of the planetary system. Figuratively speaking, we seem to be bathing in the crown of the great luminary...
The closest star to us is, of course, the Sun. According to cosmic parameters, the distance from the Earth to it is quite small: from the Sun to the Earth, sunlight travels only 8 minutes.
The Sun is not an ordinary yellow dwarf, as previously thought. This is the central body of the solar system, around which the planets revolve, with large quantity heavy elements. This is a star formed after several supernova explosions, around which a planetary system was formed. Due to the location, close to ideal conditions, life arose on the third planet Earth. The Sun is already five billion years old. But let's see why it shines? What is the structure of the Sun, and what are its characteristics? What awaits him in the future? How significant is its impact on the Earth and its inhabitants? The sun is the star around which all 9 planets of the solar system revolve, including ours. 1 a.u. (astronomical unit) = 150 million km - the same is the average distance from the Earth to the Sun. The solar system includes nine large planets, about a hundred satellites, many comets, tens of thousands of asteroids (minor planets), meteoroids and interplanetary gas and dust. At the center of all this is our Sun.
The sun has been shining for millions of years, which is confirmed by modern biological studies obtained from the remains of blue-green-blue algae. Change the temperature of the surface of the Sun by at least 10%, and on Earth, all life would die. Therefore, it is good that our star evenly radiates the energy necessary for the prosperity of mankind and other creatures on Earth. In the religions and myths of the peoples of the world, the Sun has always occupied the main place. Almost all the peoples of antiquity, the Sun was the most important deity: Helios - among the ancient Greeks, Ra - the god of the Sun of the ancient Egyptians and Yarilo among the Slavs. The sun brought warmth, harvest, everyone revered it, because without it there would be no life on Earth. The size of the Sun is impressive. For example, the mass of the Sun is 330,000 times the mass of the Earth, and its radius is 109 times greater. But the density of our stellar body is small - 1.4 times greater than the density of water. The movement of spots on the surface was noticed by Galileo Galilei himself, thus proving that the Sun does not stand still, but rotates.
convective zone of the sun
The radioactive zone is about 2/3 of the inner diameter of the Sun, and the radius is about 140 thousand km. Moving away from the center, photons lose their energy under the influence of the collision. This phenomenon is called the phenomenon of convection. This is similar to the process that takes place in a boiling kettle: the energy coming from the heating element is much greater than the amount that is removed by conduction. Hot water, located in the vicinity of the fire, rises, and the colder one falls down. This process is called convention. The meaning of convection is that a denser gas is distributed over the surface, cools and again goes to the center. The mixing process in the convective zone of the Sun is continuous. Looking through a telescope at the surface of the Sun, you can see its granular structure - granulations. The feeling is that it consists of granules! This is due to convection occurring under the photosphere.
photosphere of the sun
A thin layer (400 km) - the photosphere of the Sun, is located directly behind the convective zone and represents the "real solar surface" visible from the Earth. For the first time, the granules on the photosphere were photographed by the Frenchman Janssen in 1885. An average granule has a size of 1000 km, moves at a speed of 1 km/sec, and exists for approximately 15 minutes. Dark formations on the photosphere can be observed in the equatorial part, and then they shift. The strongest magnetic fields are a hallmark of such spots. BUT dark color obtained due to the lower temperature relative to the surrounding photosphere.
Chromosphere of the Sun
The solar chromosphere (colored sphere) is a dense layer (10,000 km) of the solar atmosphere, which is located directly behind the photosphere. It is rather problematic to observe the chromosphere, due to its close location to the photosphere. It is best seen when the Moon closes the photosphere, i.e. during solar eclipses.
Solar prominences are huge emissions of hydrogen resembling glowing long filaments. Prominences rise to great distances, reaching the diameter of the Sun (1.4 mln km), moving at a speed of about 300 km/sec, and the temperature at the same time reaches 10,000 degrees.
The solar corona is the outer and extended layers of the Sun's atmosphere, originating above the chromosphere. The length of the solar corona is very long and reaches several solar diameters. To the question of where exactly it ends, scientists have not yet received a definite answer.
The composition of the solar corona is a rarefied, highly ionized plasma. It contains heavy ions, electrons with a nucleus of helium and protons. The temperature of the corona reaches from 1 to 2 million degrees K, relative to the surface of the Sun.
The solar wind is a continuous outflow of matter (plasma) from the outer shell of the solar atmosphere. It consists of protons, atomic nuclei and electrons. The speed of the solar wind can vary from 300 km/sec to 1500 km/sec, in accordance with the processes taking place on the Sun. The solar wind propagates throughout the solar system and, interacting with magnetic field Earth causes various phenomena, one of which is the northern lights.
Characteristics of the Sun
Mass of the Sun: 2∙1030 kg (332,946 Earth masses)
Diameter: 1,392,000 km
Radius: 696,000 km
Average density: 1,400 kg/m3
Axial tilt: 7.25° (relative to the plane of the ecliptic)
Surface temperature: 5,780 K
Temperature at the center of the Sun: 15 million degrees
Spectral class: G2 V
Average distance from Earth: 150 million km
Age: 5 billion years
Rotation period: 25.380 days
Luminosity: 3.86∙1026W
Apparent magnitude: 26.75m
