part of the sun's atmosphere
Alternative descriptionsA headdress that is a symbol of monarchical power
Monarch attribute
In Russia until 1917 - a precious head adornment of the ruler as a symbol of princely, royal power
Crowns Caesar
Headdress associated with famous discovery Archimedes
Sign of royal dignity
One of the monarchical regalia
Halo around a celestial body
Tsar's cover-up
Royal crown decorated with jewels
Royal headdress
Part of a star's atmosphere
The novel by the Russian writer O. P. Smirnov “Northern...”
What is a tiara?
Symbol of power on the head
Latin "crown"
Monarch's headdress
The Elusive Ones brought her back
Crown of the King
Royal crown
Dress fit for a king
Crowns the king
Constellation South...
Golden crown
Crown (Latin)
Headdress of the king
What the monarch's head is doing
Royal crown
Royal precious headdress
His Majesty's Crown
Solar crown
Royal chocolate brand
Diadem
Solar headdress
Object placed on the royal head
Symbol of monarchical power
. (koruna) jagged decoration on the top of the icon's crown
Monarch hat
Chocolate with a royal name
Precious headdress
Symbol of royal power
Emperor's Crown
Mexican beer
What's on the king's head?
King's hat
Headdress of monarchs
Royal crown decorated with jewels
Precious headdress, an item of palace ceremonial
Halo around a celestial body
G. head decoration made of gold with expensive stones; this is one of the regalia, accessories of rulers: a crown, a golden rim, brought together by arches on the crown, with conventional signs of the degree of the ruler's rank. The papal crown is called the tiara. Iron Lombard crown, late sixth century. Charlemagne and Napoleon the First were crowned. Treasury, government. An official from the crown, not by election. Crown rampart, parapet, military. its upper plane. The crown will detract. decoration in the form of a crown; olon. girl's headdress, ribbon. Crown, related to the crown, state, from the treasury, or state-owned. Crown-shaped, crown-shaped, -shaped, made in the form of a crown. To crown someone, to place the crown on the head of a sovereign person for the first time, to perform the solemn church rite of enthronement; to crown the kingdom. -sya, to be crowned; crown yourself. Coronation Wed. coronation w. performing this ritual; first, meaning actions; second, meaning events and the celebration itself
Latin "crown"
Royal chocolate brand
The novel by the Russian writer O. P. Smirnov "Northern..."
Solar headdress
What is a tiara
What's on the king's head?
Crown of the King
Executive headdress inappropriate in a republic
Ushanka belongs to the peasant, but to the Tsar?
The atmosphere is the gaseous shell of our planet, which rotates along with the Earth. The gas in the atmosphere is called air. The atmosphere is in contact with the hydrosphere and partially covers the lithosphere. But the upper limits are difficult to determine. It is conventionally accepted that the atmosphere extends upward for approximately three thousand kilometers. There it smoothly flows into airless space.
Chemical composition of the Earth's atmosphere
Formation chemical composition the atmosphere began about four billion years ago. Initially, the atmosphere consisted only of light gases - helium and hydrogen. According to scientists, the initial prerequisites for the creation of a gas shell around the Earth were volcanic eruptions, which, along with lava, ejected huge amount gases Subsequently, gas exchange began with water spaces, with living organisms, and with the products of their activities. The composition of the air gradually changed and modern form recorded several million years ago.
The main components of the atmosphere are nitrogen (about 79%) and oxygen (20%). The remaining percentage (1%) comes from the following gases: argon, neon, helium, methane, carbon dioxide, hydrogen, krypton, xenon, ozone, ammonia, sulfur and nitrogen dioxides, nitrous oxide and carbon monoxide, which are included in this one percent.
In addition, the air contains water vapor and particulate matter (pollen, dust, salt crystals, aerosol impurities).
Recently, scientists have noted not a qualitative, but a quantitative change in some air ingredients. And the reason for this is man and his activities. In the last 100 years alone, carbon dioxide levels have increased significantly! This is fraught with many problems, the most global of which is climate change.
Formation of weather and climate
The atmosphere plays a critical role in shaping the climate and weather on Earth. A lot depends on the amount of sunlight, the nature of the underlying surface and atmospheric circulation.
Let's look at the factors in order.
1. The atmosphere transmits the heat of the sun's rays and absorbs harmful radiation. The fact that the rays of the Sun fall on different parts of the Earth under different angles, the ancient Greeks knew. The word “climate” itself translated from ancient Greek means “slope”. So, at the equator, the sun's rays fall almost vertically, which is why it is very hot here. The closer to the poles, the greater the angle of inclination. And the temperature drops.
2. Due to the uneven heating of the Earth, air currents are formed in the atmosphere. They are classified according to their sizes. The smallest (tens and hundreds of meters) are local winds. This is followed by monsoons and trade winds, cyclones and anticyclones, and planetary frontal zones.
All these air masses are constantly moving. Some of them are quite static. For example, trade winds that blow from the subtropics towards the equator. The movement of others depends largely on atmospheric pressure.
3. Atmospheric pressure is another factor influencing climate formation. This is the air pressure on the surface of the earth. As is known, air masses move from an area with high atmospheric pressure towards an area where this pressure is lower.
A total of 7 zones are allocated. The equator is a low pressure zone. Further, on both sides of the equator up to the thirties latitudes there is an area of high pressure. From 30° to 60° - low pressure again. And from 60° to the poles is a high pressure zone. Air masses circulate between these zones. Those that come from the sea to land bring rain and bad weather, and those that blow from the continents bring clear and dry weather. In places where air currents collide, atmospheric front zones are formed, which are characterized by precipitation and inclement, windy weather.
Scientists have proven that even a person’s well-being depends on atmospheric pressure. By international standards normal atmospheric pressure is 760 mm Hg. column at a temperature of 0°C. This indicator is calculated for those areas of land that are almost level with sea level. With altitude the pressure decreases. Therefore, for example, for St. Petersburg 760 mm Hg. - this is the norm. But for Moscow, which is located higher, normal pressure is 748 mm Hg.
The pressure changes not only vertically, but also horizontally. This is especially felt during the passage of cyclones.
The structure of the atmosphere
The atmosphere is reminiscent of a layer cake. And each layer has its own characteristics.
. Troposphere- the layer closest to the Earth. The "thickness" of this layer changes with distance from the equator. Above the equator, the layer extends upward by 16-18 km, in temperate zones by 10-12 km, at the poles by 8-10 km.
It is here that 80% of the total air mass and 90% of water vapor are contained. Clouds form here, cyclones and anticyclones arise. The air temperature depends on the altitude of the area. On average, it decreases by 0.65° C for every 100 meters.
. Tropopause- transition layer of the atmosphere. Its height ranges from several hundred meters to 1-2 km. The air temperature in summer is higher than in winter. For example, above the poles in winter it is -65° C. And above the equator it is -70° C at any time of the year.
. Stratosphere- this is a layer whose upper boundary lies at an altitude of 50-55 kilometers. Turbulence here is low, the content of water vapor in the air is negligible. But there is a lot of ozone. Its maximum concentration is at an altitude of 20-25 km. In the stratosphere, the air temperature begins to rise and reaches +0.8° C. This is due to the fact that the ozone layer interacts with ultraviolet radiation.
. Stratopause- a low intermediate layer between the stratosphere and the mesosphere that follows it.
. Mesosphere- the upper boundary of this layer is 80-85 kilometers. Complex photochemical processes involving free radicals occur here. They are the ones who provide that gentle blue glow of our planet, which is seen from space.
Most comets and meteorites burn up in the mesosphere.
. Mesopause- the next intermediate layer, the air temperature in which is at least -90°.
. Thermosphere- the lower boundary begins at an altitude of 80 - 90 km, and the upper boundary of the layer runs approximately at 800 km. The air temperature is rising. It can vary from +500° C to +1000° C. During the day, temperature fluctuations amount to hundreds of degrees! But the air here is so rarefied that understanding the term “temperature” as we imagine it is not appropriate here.
. Ionosphere- combines the mesosphere, mesopause and thermosphere. The air here consists mainly of oxygen and nitrogen molecules, as well as quasi-neutral plasma. The sun's rays entering the ionosphere strongly ionize air molecules. In the lower layer (up to 90 km) the degree of ionization is low. The higher, the greater the ionization. So, at an altitude of 100-110 km, electrons are concentrated. This helps to reflect short and medium radio waves.
The most important layer of the ionosphere is the upper one, which is located at an altitude of 150-400 km. Its peculiarity is that it reflects radio waves, and this facilitates the transmission of radio signals over considerable distances.
It is in the ionosphere that such a phenomenon as the aurora occurs.
. Exosphere- consists of oxygen, helium and hydrogen atoms. The gas in this layer is very rarefied and hydrogen atoms often escape into outer space. Therefore, this layer is called the “dispersion zone”.
The first scientist to suggest that our atmosphere has weight was the Italian E. Torricelli. Ostap Bender, for example, in his novel “The Golden Calf” lamented that every person is pressed by a column of air weighing 14 kg! But the great schemer was a little mistaken. An adult experiences pressure of 13-15 tons! But we do not feel this heaviness, because atmospheric pressure is balanced by the internal pressure of a person. The weight of our atmosphere is 5,300,000,000,000,000 tons. The figure is colossal, although it is only a millionth of the weight of our planet.
Atmosphere
The Earth's atmosphere is the air that we breathe, the gaseous shell of the Earth that is familiar to us. Other planets also have such shells. Stars are made entirely of gas, but their outer layers are also called atmospheres. In this case, those layers from which at least part of the radiation can freely escape into the surrounding space without being absorbed by the overlying layers are considered external.
Photosphere
The photosphere 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 conventionally 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 the middle layer, the radiation from which we perceive, is about 6000 K.
Under such conditions, almost all gas molecules disintegrate into individual atoms. Only in the uppermost layers of the photosphere are relatively few simple molecules and radicals of the type H 2, OH, and CH preserved.
A special role in the solar atmosphere is played by the negative hydrogen ion, which is not found in earthly 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, which are delivered by easily ionized atoms of calcium, sodium, magnesium, iron and other metals, “stick” to neutral hydrogen atoms. When generated, negative hydrogen ions emit most of the visible light. The ions greedily absorb this same light, which is why the opacity of the atmosphere quickly increases with depth. Therefore, the visible edge of the Sun seems very sharp to us.
Almost all of our knowledge about the Sun is based on the study of its spectrum - a narrow multi-colored strip of the same nature as a rainbow. For the first time, placing a prism in the path of a solar ray, Newton received such a stripe and exclaimed:
“Spectrum!” (Latin spectrum - “vision”). Later, dark lines were noticed in the spectrum of the Sun and considered to be the boundaries of colors. In 1815, the German physicist Joseph Fraunhofer gave the first detailed description of such lines in the solar spectrum, and they began to be called after him. It turned out that Fraunhofer lines correspond to certain parts of the spectrum that are strongly absorbed by atoms of various substances (see the article “Analysis of Visible Light”). In a telescope with high magnification, you can observe subtle details of the photosphere: it all seems strewn with small bright grains - granules, separated by a network of narrow dark paths. Granulation is the result of the mixing of warmer gas flows rising and colder ones descending. 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 occurs much more intensely. Convection in the outer layers of the Sun plays a huge role, determining general structure 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. At times, concentrated magnetic fields arise in a small region of the solar atmosphere, several times stronger than on Earth. Ionized plasma is a good conductor; it cannot mix across the magnetic induction lines 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 appears completely black, although in reality its brightness is only ten times weaker.
Over time, the size and shape of the spots change greatly. Having appeared 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. The spots are surrounded by brighter areas of the photosphere, called faculae or flare fields.
The photosphere gradually passes into the more rarefied outer layers of the solar atmosphere - the chromosphere and corona.
Chromosphere
The chromosphere (Greek: “sphere of color”) 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 less. 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 is heated in much the same way as if it were in a giant microwave oven. The speed of thermal motion of particles increases, collisions between them become more frequent, and atoms lose their outer electrons: the substance becomes a hot ionized plasma. These same physical processes They also maintain an unusually high temperature in the outermost layers of the solar atmosphere, which are located above the chromosphere.
Often during eclipses (and with the help of special spectral instruments - and without waiting for eclipses) above the surface of the Sun one can observe bizarrely shaped “fountains”, “clouds”, “funnels”, “bushes”, “arches” and other brightly luminous formations from the chromospheric substances. They can be 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 ambitious 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 surrounded by higher, highly rarefied upper layers of the solar atmosphere. Prominences do not fall into the chromosphere because their matter 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 intersects the edge of the Sun, and if a prominence is located near it, then its radiation spectrum can be seen. By directing the slit at different parts of the prominence or chromosphere, it is possible to study them in parts. The spectrum of prominences, like the chromosphere, consists of bright lines, mainly hydrogen, helium and calcium. Emission lines of others chemical elements are also present, but they are much weaker.
Some prominences, having remained for a long time without noticeable changes, suddenly seem to explode, and their matter is thrown 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 areas of the Sun's atmosphere. These are 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 glow of a separate section of the chromosphere suddenly increases tens of times. Ultraviolet and X-ray radiation increases especially strongly: sometimes its power is several times higher than the total radiation power of the Sun in this short-wave region of the spectrum before the flare.
Spots, torches, prominences, chromospheric flares - all these are manifestations of solar activity. With increasing activity, the number of these formations on the Sun increases.
Crown
Unlike the photosphere and chromosphere, the outermost part of the Sun's atmosphere - the corona - has a huge extent: it extends over 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, the force of gravity is much greater, and it would seem that its atmosphere should not be high. In reality it is extraordinarily extensive. Consequently, there are some forces acting against the attraction of the Sun. These forces are associated with the enormous 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 view crowns The observer's eye is just beginning to get used to the sudden twilight, and a bright ray of the Sun emerging from behind the edge of the Moon already announces the end of the eclipse. Therefore, sketches of the corona made by experienced observers during the same eclipse were often 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 shot of the crown is also not easy. The fact is that its 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 crown is clearly visible in photographs, the inner one turns out to be overexposed, and in photographs where the details of the inner crown are visible, the outer one is completely invisible. To overcome this difficulty, during an eclipse they usually try to take several photographs of the corona at once - with long and short shutter speeds. Or the corona is photographed by placing a special “radial” filter in front of the photographic plate, which weakens the ring zones of bright internal parts crowns In such photographs, its structure can be traced to distances of many solar radii.
Structure of the Sun
1 – core, 2 – radiative equilibrium zone, 3 – convective zone, 4 – photosphere, 5 – chromosphere, 6 – corona, 7 – spots, 8 – granulation, 9 – prominence
Internal structure of the Sun. Core
The central part of the Sun with a radius of about 150,000 km (0.2 - 0.25 solar radii), in which thermonuclear reactions occur, is called the solar core.
The density of the substance in the core is approximately 150,000 kg/m³ (150 times higher than the density of water and ~6.6 times higher than the density of the heaviest metal on Earth - iridium), and the temperature in the center of the core is more than 14 million K.
Because The highest temperatures and densities should be in the central parts of the Sun; nuclear reactions and the accompanying energy release occur most intensely near the very center of the Sun. In the nucleus, along with the proton-proton reaction, the carbon cycle plays a significant role.
As a result of the proton-proton reaction alone, 4.26 million tons of matter are converted into energy every second, but this value is insignificant compared to the mass of the Sun - 2·1027 tons. Internal structure of the Sun.
Radiant Equilibrium Zone
As you move away from the center of the Sun, the temperature and density become lower, the release of energy due to the carbon cycle quickly stops, and up to a distance of 0.2–0.3 radius, the temperature becomes less than 5 million K, and the density also drops significantly. As a result, nuclear reactions practically do not occur here. These layers only transmit radiation that occurs at greater depths outward.
It is significant that instead of each absorbed quantum of high energy, particles, as a rule, emit several quanta of lower energies as a result of successive cascade transitions. Therefore, instead of γ-quanta, X-rays appear, instead of X-rays, UV quanta appear, which, in turn, are already in the outer layers “fragmented” into quanta of visible and thermal radiation, finally emitted by the Sun.
That part of the Sun in which the release of energy due to nuclear reactions is insignificant and the process of energy transfer occurs only through absorption of radiation and subsequent re-emission is called the radiative equilibrium zone. It occupies an area from approximately 0.3 to 0.7 solar radii.
Convective zone
Above the level of radiative equilibrium, the substance itself begins to take part in energy transfer.
Directly below the observable outer layers of the Sun, over about 0.3 of its radius, a convective zone is formed in which energy is transferred by convection.
In the convective zone, vortex mixing of the plasma occurs. According to modern data, the role of the convective zone in the physics of solar processes is exceptionally great, since it is in it that various movements of solar matter and magnetic fields originate.
The structure of the solar atmosphere. Photosphere
The outermost layers of the Sun (the solar atmosphere) are usually divided into the photosphere, chromosphere and corona.
The photosphere is that part of the solar atmosphere in which visible radiation is formed, which has a continuous spectrum. Thus, almost all solar energy coming to us is emitted in the photosphere. The photosphere is visible when directly observing the Sun in white light in the form of its apparent “surface”.
The thickness of the photosphere, i.e. The length of the layers, from where more than 90% of the radiation in the visible range comes, is less than 200 km, i.e. about 3·10–4 R. As calculations show, when observed tangentially to such layers, their apparent thickness decreases several times, as a result of which, near the very edge of the solar disk (limb), the fastest drop in brightness occurs over a period of less than 10–4 R. For this reason, the edge of the Sun appears exceptionally sharp. The concentration of particles in the photosphere is 1016–1017 per 1 cm3 (under normal conditions, 1 cm3 of the earth’s atmosphere contains 2.7 1019 molecules). The pressure in the photosphere is about 0.1 atm, and the temperature of the photosphere is 5,000 – 7,000 K.
Under such conditions, atoms with ionization potentials of several volts (Na, K, Ca) are ionized. The remaining elements, including hydrogen, remain predominantly in a neutral state.
The photosphere is the only region of neutral hydrogen on the Sun. However, as a result of insignificant ionization of hydrogen and almost complete ionization of metals, it still contains free electrons. These electrons play an extremely important role: when they combine with neutral hydrogen atoms, they form negative hydrogen ions H -
Negative hydrogen ions are formed in negligible quantities: out of 100 million hydrogen atoms, on average, only one turns into a negative ion.
H– ions have the property of unusually strongly absorbing radiation, especially in the IR and visible regions of the spectrum. Therefore, despite their insignificant concentration, negative hydrogen ions are the main reason determining the absorption of radiation in the visible region of the spectrum by photospheric matter. The bond between the second electron and the atom is very weak, and therefore even IR photons can destroy the negative hydrogen ion.
Radiation occurs when electrons are captured by neutral atoms. Formed upon capture
photons determine the glow of the photospheres of the Sun and stars close to it in temperature. Thus, yellowish
The light of the Sun, which is commonly called “white,” arises when another electron is added to a hydrogen atom.
The electron affinity of a neutral H atom is 0.75 eV. When an electron ( e) with energy greater than 0.75 eV, its excess is carried away electromagnetic radiation e+H → H– + ħ ω, a significant part of which falls in the visible range.
Observations of the photosphere reveal its fine structure, reminiscent of closely spaced cumulus clouds. Light round formations are called granules, and the entire structure is called granulation. The angular dimensions of the granules on average are no more than 1" arc, which corresponds to 725 km on the Sun. Each individual granule exists for an average of 5–10 minutes, after which it disintegrates, and in its place appear
The granules are surrounded by dark spaces, forming cells or honeycombs. The spectral lines in the granules and in the spaces between them are shifted to the blue and red sides, respectively. This means that the substance in the granules rises and around them sinks. The speed of these movements is 1–2 km/s.
Granulation is a manifestation of the convective zone located under the photosphere observed in the photosphere. In the convective zone, active mixing of matter occurs as a result of the rise and fall of individual masses of gas (convection elements). Having traveled a path approximately equal to their size, they seem to dissolve into environment, generating new inhomogeneities. In the outer, colder layers,
the sizes of these heterogeneities are smaller
Chromosphere
In the outer layers of the photosphere, where the density decreases to 3×10-8 g/cm3, the temperature reaches values below 4,200 K. This temperature value turns out to be the minimum for the entire solar atmosphere. In more high layers the temperature begins to rise again. First, there is a slow increase in temperature to several tens of thousands of kelvins, accompanied by the ionization of hydrogen and then helium. This part of the solar atmosphere is called the chromosphere.
The reason for such strong heating of the outermost layers of the solar atmosphere is the energy of acoustic (sound) waves, which arise in the photosphere as a result of the movement of convection elements.
In the uppermost layers of the convective zone, directly below the photosphere, convective movements are sharply slowed down and convection suddenly stops. Thus, the photosphere from below is constantly, as it were, “bombarded” by convective elements. From these impacts, disturbances arise in it, observed in the form of granules, and it itself begins to oscillate with a period corresponding to the frequency of the photosphere’s own oscillations (about 5 minutes). These vibrations and disturbances that arise in the photosphere generate waves in it that are close in nature to sound waves in the air. When spreading upward, i.e. into layers with lower density, these waves increase their amplitude to several kilometers and turn into
shock waves.
The length of the chromosphere is several thousand km. The chromosphere has an emission spectrum consisting of bright lines. This spectrum is very similar to the spectrum of the Sun, in which all absorption lines are replaced by emission lines, and there is almost no continuous spectrum. However, in the spectrum of the chromosphere, the lines of ionized elements are stronger than in the spectrum of the photosphere. In particular, helium lines are very strong in the spectrum of the chromosphere, while in the Fraunhofer spectrum they are practically invisible. These spectral features confirm an increase in temperature in the chromosphere.
When studying images of the chromosphere, the first thing that attracts attention is its inhomogeneous structure, which is much more pronounced than granulation in the photosphere.
The smallest structural formations in the chromosphere are called spicules. They have an oblong shape, and are elongated mainly in the radial direction. Their length is several thousand km, and their thickness is about 1,000 km. At speeds of several tens of km/s, spicules rise from the chromosphere into the corona and dissolve in it.
Through spicules, the substance of the chromosphere is exchanged with the overlying corona.
There are hundreds of thousands of spicules existing on the Sun at the same time.
The spicules in turn form a larger structure called the chromospheric network, generated by wave motions caused by much larger and deeper elements
subphotospheric convective zone than granules.
The chromospheric network is best seen in images with strong lines in the far UV region of the spectrum,
for example, in the 304 Å resonance line of ionized helium.
The chromospheric network consists of individual cells ranging in size from 30 to 60 thousand km.
Crown
In the upper layers of the chromosphere, where the gas density is only 10–15 g/cm3, another extraordinary thing occurs sharp increase temperatures up to about a million kelvins. This is where the outermost and thinnest part of the Sun's atmosphere, called the solar corona, begins.
The brightness of the solar corona is a million times less than the photosphere, and does not exceed the brightness of the Moon at full moon. Therefore, the solar corona can be observed during the total phase of solar eclipses, and outside of eclipses - with the help of special telescopes (coronagraphs), in which an artificial eclipse of the Sun is arranged.
The crown does not have sharp outlines and has an irregular shape that changes greatly over time. This can be judged by comparing its images obtained during various eclipses. The brightest part of the corona, located no more than 0.2-0.3 solar radii from the limb, is usually called the inner corona, and the rest, a very extended part, is the outer corona. An important feature of the crown is its radiant structure. The rays come in various lengths up to a dozen or more solar radii. At the base, the rays usually thicken, some of them bend towards the neighboring ones.
The spectrum of the corona has a number of important features. It is based on a weak continuous background with an energy distribution that repeats the energy distribution in the continuous spectrum of the Sun. Against this background
continuous spectrum, bright emission lines are observed in the inner corona, the intensity of which decreases with distance from the Sun. Most of these lines cannot be obtained in laboratory spectra. In the outer corona, Fraunhofer lines of the solar spectrum are observed, which differ from the photospheric lines in their relatively greater residual intensity.
The corona radiation is polarized, and at a distance of about 0.5 Rfrom the edge of the Sun the polarization increases to approximately 50%, and at greater distances it decreases again.__
Corona radiation is scattered light from the photosphere, and the polarization of this radiation makes it possible to establish the nature of the particles on which scattering occurs - these are free electrons.
The appearance of these free electrons can only be caused by the ionization of the substance. However, in general, the ionized gas (plasma) must be neutral. Therefore, the concentration of ions in the corona must also correspond to the concentration of electrons.
The emission lines of the solar corona belong to ordinary chemical elements, but in very high stages of ionization. The most intense - green coronal line with a wavelength of 5303 Å - is emitted by the Fe XIV ion, i.e. an iron atom lacking 13 electrons. Another intense one - the red coronal line (6,374 Å) - belongs to the atoms of ninefold ionized iron Fe X. The remaining emission lines are identified with the ions Fe XI, Fe XIII, Ni XIII, Ni XV, Ni XVI, Ca XII, Ca XV, Ar X and etc.
Thus, the solar corona is a rarefied plasma with a temperature of about a million kelvins.
Zodiacal light and counterradiance
A glow similar to the “false corona” can also be observed at great distances from the Sun in
form of zodiacal light.
Zodiacal light is observed on dark moonless nights in spring and autumn in southern latitudes soon
after sunset or shortly before sunrise. At this time, the ecliptic rises high above the horizon, and a light stripe running along it becomes noticeable. As it approaches the Sun, which is below the horizon, the glow intensifies and the stripe expands, forming a triangle. Its brightness gradually decreases with increasing distance from the Sun.
In the area of the sky opposite the Sun, the brightness of the zodiacal light increases slightly, forming an elliptical nebulous spot with a diameter of about 10º, which is called the antiradiance. Counter-shine
caused by the reflection of sunlight from cosmic dust.
solar wind
The solar corona has a dynamic continuation far beyond the Earth's orbit to distances of the order of 100 AU.
There is a constant outflow of plasma from the solar corona at a speed that gradually increases with distance from the Sun. This expansion of the solar corona into interplanetary space is called the solar wind.
Due to the solar wind, the Sun loses about 1 million tons of matter every second. The solar wind consists primarily of electrons, protons, and helium nuclei (alpha particles); the nuclei of other elements and neutral particles are contained in very small quantities.
The solar wind (the flow of particles - protons, electrons, etc.) is often confused with the pressure effect of sunlight (the flow of photons). The pressure of sunlight is currently several thousand times greater than the pressure of the solar wind. The tails of comets, always directed in the opposite direction from the Sun, are also formed due to the pressure of light, and not due to the solar wind.
38. Active formations in the solar atmosphere: spots, faculae, flocculi, chromospheric flares, prominences. Cyclicity of solar activity.
Active formations in the solar atmosphere
From time to time, rapidly changing active formations appear in the solar atmosphere, sharply different from the surrounding undisturbed regions, the properties and structure of which do not change at all or almost completely with time. In the photosphere, chromosphere and corona, the manifestations of solar activity are very different. However, they are all connected by a common reason. This reason is the magnetic field, always
present in active regions.
The origin and cause of changes in magnetic fields on the Sun are not fully understood. Magnetic fields can be concentrated in any layer of the Sun (for example, at the base of the convective zone), and periodic increases in magnetic fields can be caused by additional excitations of currents in the solar plasma.
The most common manifestations of solar activity are spots, faculae, flocculi, and prominences.
Sunspots
The most famous manifestation of solar activity are sunspots, which usually appear in entire groups.
The sunspot appears as a tiny pore, barely distinguishable from the dark spaces between the granules. After a day, the pore develops into a round dark spot with a sharp boundary, the diameter of which gradually increases up to a size of several tens of thousands of km. This phenomenon is accompanied by a gradual increase in the magnetic field strength, which in the center of large spots reaches several thousand oersteds. The magnitude of the magnetic field is determined by the Zeeman splitting of spectral lines.
Sometimes several small spots appear within a small area extended parallel to the equator - a group of spots. Individual spots predominantly appear on the western and eastern edges of the area, where the bottoms of the spot - the leading (western) and tail (eastern) - develop more strongly than others. The magnetic fields of both main sunspots and the small ones adjacent to them always have opposite polarity, and therefore such a group of sunspots is called bipolar
3-4 days after the appearance of large spots, a less dark penumbra appears around them, having a characteristic radial structure. The penumbra surrounds the central part of the sunspot, called the umbra.
Over time, the area occupied by a group of spots gradually increases, reaching its maximum
values approximately on the tenth day. After this, the spots begin to gradually decrease and disappear, first the smallest of them, then the tail (having previously broken up into several spots), and finally the leading one.
In general, this entire process lasts about two months, but many groups of sunspots do not have time to
go through all the stages described and disappear earlier.
The central part of the spot only appears black due to the high brightness of the photosphere. In fact, in the center
The brightness of the spots is only an order of magnitude less, and the brightness of the penumbra is approximately 3/4 of the brightness of the photosphere. Based on the Stefan-Boltzmann law, this means that the temperature in the sunspot is 2–2.5 thousand K less than in the photosphere.
The decrease in temperature in the sunspot is explained by the influence of the magnetic field on convection. A strong magnetic field inhibits the movement of matter occurring across the lines of force. Therefore, in the convective zone under the sunspot, the circulation of gases, which transfers a significant part of the energy from the depths outward, is weakened. As a result, the temperature of the spot turns out to be lower than in the undisturbed photosphere.
The large concentration of the magnetic field in the shadow of the leading and tail sunspots suggests that the main part of the magnetic flux of the active region on the Sun is contained in a giant tube of field lines emerging from the shadow of the north polarity sunspot and entering back into the south polarity sunspot.
However, due to the high conductivity of solar plasma and the phenomenon of self-induction, magnetic fields with a strength of several thousand oersteds can neither arise nor disappear within a few days corresponding to the time of appearance and decay of a group of sunspots.
Thus, it can be assumed that magnetic tubes are located somewhere in the convective zone, and the emergence of groups of sunspots is associated with the floating of such tubes.
Torches
In undisturbed regions of the photosphere there is only a general magnetic field of the Sun, the strength of which is about 1 Oe. In active regions, the magnetic field strength increases hundreds and even thousands of times.
A slight increase in the magnetic field to tens and hundreds of Oe is accompanied by the appearance in the photosphere of a brighter region called a torch. In total, faculae can occupy a significant proportion of the entire visible surface of the Sun. They have a characteristic fine structure and consist of numerous veins, bright dots and nodules - torch granules.
The faculae are best visible at the edge of the solar disk (here their contrast with the photosphere is about 10%), while in the center they are almost completely invisible. This means that at some level in the photosphere the plume is hotter than the neighboring undisturbed region by 200–300 K and, on the whole, slightly protrudes above the level
undisturbed photosphere.
The appearance of a torch is associated with an important property of the magnetic field - it prevents the movement of ionized matter occurring across the lines of force. If the magnetic field has enough great energy, then it “allows” the movement of matter only along the lines of force.
A weak magnetic field in the plume region cannot stop relatively powerful convective movements. However, it can give them a more correct character. Typically, each element of convection, in addition to the general rise or fall in the vertical, makes small random movements in the horizontal plane. These movements, which lead to friction between the individual elements of convection, are inhibited by the magnetic field present in the plume region, which facilitates convection and allows hot gases to rise to a greater height and transfer a greater flow of energy. Thus, the appearance of the plume is associated with increased convection caused by a weak magnetic field.
Torches are relatively stable formations. They can exist for several weeks or even months without much change.
Floccules
The chromosphere above sunspots and faculae increases its brightness, and the contrast between the disturbed and undisturbed chromosphere increases with height. These brighter regions of the chromosphere are called flocculi. An increase in the brightness of a floccule compared to the surrounding undisturbed chromosphere does not provide grounds for determining its temperature, since in a rarefied and very transparent chromosphere for a continuous spectrum, the relationship between temperature and radiation does not obey the Planck and Stefan-Boltzmann laws.
The increase in the brightness of the floccule in the central parts can be explained by an increase in the density of matter in the chromosphere by 3–5 times at an almost constant temperature value, or with a slight increase in temperature. Solar flares
In the chromosphere and corona, most often in a small region between developing sunspots, especially near the polarity interface of strong magnetic fields, the most powerful and rapidly developing manifestations of solar activity, called solar flares, are observed.
At the beginning of the flare, the brightness of one of the light nodules of the flocculus suddenly increases. Often in less than a minute, strong radiation spreads along a long rope or floods an entire area tens of thousands of kilometers long.
In the visible region of the spectrum, the increase in luminescence occurs mainly in the spectral lines of hydrogen, ionized calcium and other metals. The level of the continuum also increases, sometimes so much that the flash becomes visible in white light against the background of the photosphere. Simultaneously with visible radiation, the intensity of UV and X-ray radiation, as well as the power of solar radio emission, increases greatly.
During flares, the shortest wavelength (i.e., the “hardest”) X-ray spectral lines and even, in some cases, γ-rays are observed. The burst of all these types of radiation occurs in a few minutes. After reaching the maximum, the radiation level gradually weakens over several tens of minutes.
All of the above phenomena are explained by the release large quantity energy of unstable plasma located in the region of a very inhomogeneous magnetic field. As a result of the interaction of the magnetic field and plasma, a significant part of the energy of the magnetic field turns into heat, heating the gas to a temperature of tens of millions of kelvins, and also goes to accelerate plasma clouds.
Simultaneously with the acceleration of macroscopic plasma clouds, the relative movements of the plasma and magnetic fields lead to the acceleration of individual particles to high energies: electrons up to tens of keV and protons up to tens of MeV.
The flow of such solar particles has a significant impact on the upper layers of the Earth's atmosphere and its magnetic field.
Prominences
The active formations observed in the corona are prominences. Compared to the surrounding plasma, these are denser and “colder” clouds, glowing in approximately the same spectral lines as the chromosphere.
Prominences can be very various forms and sizes. Most often these are long, very flat formations located almost perpendicular to the surface of the Sun. Therefore, when projected onto the solar disk, prominences look like curved filaments.
Prominences are the largest formations in the solar atmosphere, their length reaches hundreds of thousands of km, although their width does not exceed 6,000–10,000 km. Their lower parts merge with the chromosphere, and their upper parts extend for tens of thousands of km. However, there are prominences of much larger sizes.
The exchange of matter between the chromosphere and the corona constantly occurs through the prominences. This is evidenced by the frequently observed movements of both the prominences themselves and their individual parts, occurring at speeds of tens and hundreds of km/s.
The emergence, development and movement of prominences is closely related to the evolution of sunspot groups. At the first stages of development of the active region, short-lived and rapidly changing sunspots are formed.
prominences near sunspots. At later stages, stable quiet prominences appear, existing without noticeable changes for several weeks and even months, after which a stage of activation of the prominence may suddenly occur, manifested in the occurrence of strong movements, ejections of matter into the corona and the appearance of rapidly moving eruptive prominences.
Eruptive, or eruptive, resemble huge fountains in appearance, reaching heights of up to 1.7 million km above the surface of the Sun. The movements of clots of matter in them occur quickly; erupt at speeds of hundreds of km/s and change their shape quite quickly. As the altitude increases, the prominence weakens and dissipates. In some prominences, sharp changes in the speed of movement of individual clumps were observed. Eruptive prominences are short-lived.
Solar activity
All considered active formations in the solar atmosphere are closely related to each other.
The appearance of flares and flocculi always precedes the appearance of spots.
Outbreaks occur during the most rapid growth of a group of sunspots or as a result of strong changes occurring in them.
At the same time, prominences appear, which often continue to exist for a long time after the collapse of the active region.
The totality of all manifestations of solar activity associated with a given part of the atmosphere and developing over a certain time is called the center of solar activity.
The number of sunspots and other associated manifestations of solar activity changes periodically. The era when the number of activity centers is greatest is called the maximum of solar activity, and when there are none or almost none at all, it is called the minimum.
As a measure of the degree of solar activity, the so-called. Wolf numbers proportional to the sum total number spots f and ten times the number of their groups g: W= k(f+ 10g).
Proportionality factor k depends on the power of the tool used. Typically, Wolf numbers are averaged (for example, over months or years) and a graph of the dependence of solar activity on
The solar activity curve shows that maxima and minima alternate on average every 11 years, although the time intervals between individual successive maxima may
range from 7 to 17 years.
During the minimum period, there are usually no spots on the Sun for some time. They then begin to appear far from the equator, at approximately ±35° latitudes. Subsequently, the spot formation zone gradually descends towards the equator. However, in areas less than 8° from the equator, spots are very rare.
An important feature of the solar activity cycle is the law of changes in the magnetic polarity of sunspots. During each 11-year cycle, all leading spots of bipolar groups have some polarity in the northern hemisphere and the opposite in the southern. The same is true for tail spots, in which the polarity is always opposite to that of the leading spot. In the next cycle, the polarity of the leading and tail spots is reversed. At the same time, the polarity of the general magnetic field of the Sun changes, the poles of which are located near the poles of rotation.
Many other characteristics also have an eleven-year cyclicity: the proportion of the Sun's area occupied by faculae and flocculi, the frequency of flares, the number of prominences, as well as the shape of the corona and
solar wind power.
The cyclicity of solar activity is one of the most important problems of modern solar physics, which has not yet been fully resolved.
When we observe a sunny summer landscape, it seems to us that the whole picture is flooded with light. However, if we look at the sun with the help of special instruments, we will find that its entire surface resembles a giant sea, where fiery waves rage and spots move. What are the main components of the solar atmosphere? What processes occur inside our star and what substances are included in its composition?
General information
The Sun is a celestial body that is a star, and the only one in the Solar System. Planets, asteroids, satellites and other space objects revolve around it. The chemical composition of the Sun is approximately the same at any point on it. However, it changes significantly as it approaches the center of the star, where its core is located. Scientists have discovered that the solar atmosphere is divided into several layers.
What chemical elements make up the Sun?
Humanity has not always had the data about the Sun that science has today. Once upon a time, supporters of the religious worldview argued that the world cannot be known. And as confirmation of their ideas, they cited the fact that it is not possible for a person to know what the chemical composition of the Sun is. However, progress in science has convincingly proven the fallacy of such views. Scientists have especially advanced in the study of stars after the invention of the spectroscope. Scientists study the chemical composition of the Sun and stars using spectral analysis. So, they found out that the composition of our star is very diverse. In 1942, researchers discovered that there was even gold in the Sun, although not much of it.
Other substances
The chemical composition of the Sun mainly includes elements such as hydrogen and helium. Their predominance characterizes the gaseous nature of our star. The content of other elements, for example, magnesium, oxygen, nitrogen, iron, calcium, is insignificant.
Using spectral analysis, researchers found out what substances are definitely not on the surface of this star. For example, chlorine, mercury and boron. However, scientists suggest that these substances, in addition to the basic chemical elements that make up the Sun, may be located in its core. Almost 42% of our star consists of hydrogen. Approximately 23% comes from all the metals that are part of the Sun.
Like most parameters of other celestial bodies, the characteristics of our star are calculated only theoretically using computer technology. The initial data are indicators such as the radius of the star, its mass and its temperature. Scientists have now determined that the chemical composition of the Sun is represented by 69 elements. Spectral analysis plays a major role in these studies. For example, thanks to him, the composition of the atmosphere of our star was established. An interesting pattern was also discovered: the set of chemical elements in the composition of the Sun is surprisingly similar to the composition of stony meteorites. This fact is important evidence in favor of the fact that these celestial bodies have a common origin.
Fire crown
It is a layer of highly rarefied plasma. Its temperature reaches 2 million Kelvin, and the density of the substance exceeds the density of the earth’s atmosphere by hundreds of millions of times. Here the atoms cannot be in a neutral state; they constantly collide and ionize. The crown is powerful source ultraviolet radiation. Our entire planetary system is exposed to the solar wind. Its initial speed is almost 1 thousand km/sec, but as it moves away from the star it gradually decreases. The speed of the solar wind at the surface of the earth is approximately 400 km/sec.
General ideas about the crown
The solar crown is sometimes called the atmosphere. However, it is only its external part. The easiest time to observe the corona is during a total eclipse. However, it will be very difficult to sketch it, because the eclipse lasts only a few minutes. When photography was invented, astronomers were able to get an objective picture of the solar corona.
After the first images were taken, researchers were able to detect areas that are associated with increased activity of the star. The Sun's corona has a radiant structure. It is not only the hottest part of its atmosphere, but is also the closest to our planet. In fact, we are constantly within its boundaries, because the solar wind penetrates into the most remote corners of the solar system. However, we are protected from its radiation effects by the earth's atmosphere.
Core, chromosphere and photosphere
The central part of our star is called the core. Its radius is equal to approximately a quarter of the total radius of the Sun. The matter inside the core is very compressed. Closer to the surface of the star is the so-called convective zone, where the movement of matter occurs, generating a magnetic field. Finally, the visible surface of the Sun is called the photosphere. It is a layer more than 300 km thick. It is from the photosphere that solar radiation comes to Earth. Its temperature reaches approximately 4800 Kelvin. Hydrogen here remains practically neutral. Above the photosphere is the chromosphere. Its thickness is about 3 thousand km. Although the chromosphere and the solar corona are located above the photosphere, scientists do not draw clear boundaries between these layers.
Prominences
The chromosphere has a very low density and is inferior in radiation intensity to the solar corona. However, here you can see interesting phenomenon: giant flames, several thousand kilometers high. They are called solar prominences. Sometimes prominences rise to a height of up to a million kilometers above the surface of the star.
Research
Prominences are characterized by the same density indicators as the chromosphere. However, they are located directly above it and are surrounded by its sparse layers. For the first time in the history of astronomy, prominences were observed by French researcher Pierre Jansen and his English colleague Joseph Lockyer in 1868. Their spectrum includes several bright lines. The chemical composition of the Sun and prominences is very similar. It mainly contains hydrogen, helium and calcium, and the presence of other elements is negligible.
Some prominences, having existed for a certain period of time without visible changes, suddenly explode. Their substance is ejected into nearby outer space at a gigantic speed, reaching several kilometers per second. Appearance chromosphere changes frequently, which indicates various processes, occurring on the surface of the Sun, including the movement of gases.
In regions of the star with increased activity, one can observe not only prominences, but also spots, as well as increased magnetic fields. Sometimes, with the help of special equipment, flares of especially dense gases are detected on the Sun, the temperature of which can reach enormous values.
Chromospheric flares
Sometimes the radio emission from our star increases hundreds of thousands of times. This phenomenon is called a chromospheric flare. It is accompanied by the formation of spots on the surface of the Sun. At first, the flares were noticed in the form of an increase in the brightness of the chromosphere, but later it turned out that they represent a whole complex various phenomena: a sharp increase in radio emission (X-ray and gamma radiation), mass ejection from the corona, proton flares.
Drawing conclusions
So, we found out that the chemical composition of the Sun is mainly represented by two substances: hydrogen and helium. Of course, there are other elements, but their percentage is low. In addition, scientists have not discovered any new chemicals, which would be part of the star and at the same time would be absent from Earth. Visible radiation is formed in the solar photosphere. It, in turn, is of enormous importance for maintaining life on our planet.
The sun is a hot body that continuously emits. Its surface is surrounded by a cloud of gases. Their temperature is not as high as that of the gases inside the star, but it is still impressive. Spectral analysis allows us to find out from a distance what the chemical composition of the Sun and stars is. And since the spectra of many stars are very similar to the spectra of the Sun, this means that their composition is approximately the same.
Today, the processes occurring on the surface and inside the main star of our planetary system, including the study of its chemical composition, are studied by astronomers in special solar observatories.