Solar radiation and its impact on the human body and climate. The impact of solar radiation on humans

The sun is a source of light and heat, which all life on Earth needs. But in addition to photons of light, it emits hard ionizing radiation, consisting of nuclei and protons of helium. Why is this happening?

Causes of solar radiation

Solar radiation is generated in the daytime during chromospheric flares - giant explosions that occur in the Sun's atmosphere. Part of the solar matter is ejected into outer space, forming cosmic rays, mainly consisting of protons and a small amount of helium nuclei. These charged particles reach the earth's surface 15-20 minutes after the solar flare becomes visible.

The air cuts off the primary cosmic radiation, giving rise to a cascade nuclear shower, which fades with decreasing altitude. In this case, new particles are born - pions, which decay and turn into muons. They penetrate into the lower layers of the atmosphere and fall to the ground, burrowing up to 1500 meters deep. It is muons that are responsible for the formation of secondary cosmic radiation and natural radiation that affects a person.

Spectrum of solar radiation

The spectrum of solar radiation includes both short-wave and long-wave regions:

gamma rays;
x-ray radiation;
UV radiation;
visible light;
infrared radiation.

Over 95% of the solar radiation falls on the region of the "optical window" - the visible part of the spectrum with adjacent regions of ultraviolet and infrared waves. As it passes through the layers of the atmosphere, the action of the sun's rays is weakened - all ionizing radiation, x-rays and almost 98% of ultraviolet are retained by the earth's atmosphere. Visible light reaches the ground almost without loss. infrared radiation, although they are also partially absorbed by gas molecules and dust particles in the air.

In this regard, solar radiation does not lead to a noticeable increase radioactive radiation on the surface of the earth. The contribution of the Sun, together with cosmic rays, to the formation of the total annual radiation dose is only 0.3 mSv/year. But this is an average value, in fact, the level of radiation incident on the ground is different and depends on geographical location terrain.

Where is solar ionizing radiation stronger?

The greatest power of cosmic rays is fixed at the poles, and the least - at the equator. This is due to the fact that the Earth's magnetic field deflects charged particles falling from space towards the poles. In addition, the radiation increases with height - at an altitude of 10 kilometers above sea level, its figure increases by 20-25 times. Active effects of higher doses solar radiation residents of the highlands are exposed, since the atmosphere in the mountains is thinner and easier to shoot through from the sun by the streams of gamma quanta and elementary particles.

Important. A radiation level of up to 0.3 mSv/h does not have a serious impact, but at a dose of 1.2 µSv/h it is recommended to leave the area, and in case of emergency, stay on its territory for no more than six months. If the readings are doubled, you should limit your stay in this area to three months.

If above sea level the annual dose of cosmic radiation is 0.3 mSv / year, then with an increase in height every hundred meters this figure increases by 0.03 mSv / year. After carrying out small calculations, we can conclude that a weekly vacation in the mountains at an altitude of 2000 meters will give an exposure of 1 mSv / year and provide almost half of the total annual norm (2.4 mSv / year).

It turns out that the inhabitants of the mountains receive an annual dose of radiation many times higher than the norm, and should suffer from leukemia and cancer more often than people living on the plains. Actually, it is not. On the contrary, lower mortality from these diseases is recorded in mountainous regions, and part of the population is long-livers. This confirms the fact that a long stay in places of high radiation activity does not negative impact on the human body.

Solar flares - high radiation hazard

Flares on the Sun are a great danger to humans and all life on Earth, since the density of the solar radiation flux can exceed the usual level of cosmic radiation by a thousand times. Thus, the outstanding Soviet scientist A. L. Chizhevsky connected the periods of sunspot formation with epidemics of typhus (1883-1917) and cholera (1823-1923) in Russia. On the basis of the graphs he made, back in 1930, he predicted the emergence of an extensive cholera pandemic in 1960-1962, which began in Indonesia in 1961, then quickly spread to other countries in Asia, Africa and Europe.

Today, a lot of data has been received that testifies to the connection of eleven-year cycles of solar activity with outbreaks of diseases, as well as with mass migrations and seasons of rapid reproduction of insects, mammals and viruses. Hematologists have found an increase in the number of heart attacks and strokes during periods of maximum solar activity. Such statistics are due to the fact that at this time people have increased blood clotting, and since in patients with heart disease the compensatory activity is depressed, there are malfunctions in its work, up to necrosis of the heart tissue and hemorrhages in the brain.

Large solar flares do not occur as often - once every 4 years. At this time, the number and size of spots increases, powerful coronal rays are formed in the solar corona, consisting of protons and a small amount of alpha particles. Astrologers registered their most powerful stream in 1956, when the density of cosmic radiation on the earth's surface increased by 4 times. Another consequence of such solar activity was Polar Lights, recorded in Moscow and the Moscow region in 2000.

How to protect yourself?

Of course, the increased background radiation in the mountains is not a reason to refuse trips to the mountains. True, it is worth thinking about safety measures and going on a trip with a portable radiometer, which will help control the level of radiation and, if necessary, limit the time spent in dangerous areas. In an area where the meter reading shows an ionizing radiation value of 7 μSv / h, you should not stay for more than one month.

The sun (astro. ☉) is the only star in the solar system. Other objects of this system revolve around the Sun: planets and their satellites, dwarf planets and their satellites, asteroids, meteoroids, comets and cosmic dust.

The internal structure of the Sun

Our Sun is a huge luminous ball of gas, within which complex processes take place and as a result, energy is continuously released. The internal volume of the Sun can be divided into several regions; the matter in them differs in its properties, and the energy is distributed through different physical mechanisms. Let's get to know them, starting from the very center.

In the central part of the Sun is the source of its energy, or, figuratively speaking, that "stove" that heats it and does not allow it to cool. This area is called the core. Under the weight of the outer layers, the matter inside the Sun is compressed, and the deeper, the stronger. Its density increases towards the center along with an increase in pressure and temperature. In the core, where the temperature reaches 15 million kelvins, energy is released.

This energy is released as a result of the fusion of atoms of light chemical elements into atoms of heavier ones. In the interior of the Sun, four hydrogen atoms form one helium atom. It was this terrible energy that people learned to release in an explosion. hydrogen bomb. It is hoped that in the near future a person will be able to learn how to use it in peaceful purposes(in 2005, news feeds broadcast about the start of construction of the first international fusion reactor in France).

The core has a radius of no more than a quarter of the total radius of the Sun. However, half of the solar mass is concentrated in its volume and almost all the energy that supports the glow of the Sun is released. But the energy of the hot core must somehow go outside, to the surface of the Sun. Exist various ways energy transfer depending on physical conditions media, namely: radiative transport, convection and heat conduction. Thermal conductivity does not play a big role in the energy processes in the Sun and stars, while radiative and convective transport is very important.

Immediately around the nucleus, a zone of radiant energy transfer begins, where it propagates through the absorption and emission of a portion of light by the substance - quanta. Density, temperature and pressure decrease as you move away from the core, and energy flows in the same direction. In general, this process is extremely slow. For quanta to get from the center of the Sun to the photosphere, many thousands of years are needed: after all, being re-emitted, quanta change direction all the time, moving back almost as often as forward.

Gamma quanta are born in the center of the Sun. Their energy is millions of times greater than the energy of visible light quanta, and the wavelength is very small. Along the way, the quanta undergo amazing transformations. A separate quantum is first absorbed by some atom, but is immediately re-emitted; most often in this case, not one previous quantum appears, but two or more. According to the law of conservation of energy, their total energy is conserved, and therefore the energy of each of them decreases. This is how quanta of lower and lower energies arise. Powerful gamma quanta seem to be split into less energetic quanta - first x-ray, then ultraviolet and

finally visible and infrared rays. Eventually the largest number The Sun radiates energy into visible light and it is no coincidence that our eyes are sensitive to it.

As we have already said, a quantum takes a very long time to seep through the dense solar matter to the outside. So if the “stove” inside the Sun suddenly went out, then we would know about it only millions of years later. On its way through the inner solar layers, the energy flow encounters a region where the opacity of the gas increases greatly. This is the convective zone of the Sun. Here, energy is no longer transferred by radiation, but by convection.

What is convection?

When a liquid boils, it is stirred. Gas can behave in the same way. Huge streams of hot gas rise up, where they give off their heat environment, and the cooled solar gas descends. It looks like the solar matter is boiling and stirring. The convective zone begins approximately at a distance of 0.7 radius from the center and extends almost to the most visible surface of the Sun (photosphere), where the transfer of the main energy flux again becomes radiant. However, due to inertia, hot streams from deeper, convective layers still penetrate here. The pattern of granulation on the surface of the Sun, well known to observers, is a visible manifestation of convection.

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 convection phenomenon. 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 heat 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 - granulation. 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. And the dark color is 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), move at a speed of about 300 km/sec, and the temperature at the same time reaches 10,000 degrees.

solar corona

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.

Sun radiation

The sun radiates its energy in all wavelengths, but in different ways. Approximately 44% of the radiation energy is in the visible part of the spectrum, and the maximum corresponds to the yellow-green color. About 48% of the energy lost by the Sun is carried away by infrared rays of the near and far range. Gamma rays, X-rays, ultraviolet and radio radiation account for only about 8%.

The visible part of solar radiation, when studied with the help of spectrum-analyzing instruments, turns out to be inhomogeneous - absorption lines are observed in the spectrum, first described by J. Fraunhofer in 1814. These lines arise when photons of certain wavelengths are absorbed by atoms of various chemical elements in the upper, relatively cold, layers of the Sun's atmosphere. Spectral analysis makes it possible to obtain information about the composition of the Sun, since a certain set of spectral lines extremely accurately characterizes chemical element. So, for example, with the help of observations of the spectrum of the Sun, the discovery of helium was predicted, which was isolated on Earth later.

Types of radiation

In the course of observations, scientists found that the Sun is a powerful source of radio emission. Radio waves penetrate into interplanetary space, which are emitted by the chromosphere (centimeter waves) and the corona (decimeter and meter waves). The radio emission of the Sun has two components - constant and variable (bursts, "noise storms"). During strong solar flares, the radio emission from the Sun increases thousands and even millions of times compared to the radio emission from the quiet Sun. This radio emission has a non-thermal nature.

X-rays come mainly from the upper layers of the chromosphere and the corona. The radiation is especially strong during the years of maximum solar activity.

The sun radiates not only light, heat and all other types of electromagnetic radiation. It is also a source of a constant flow of particles - corpuscles. Neutrinos, electrons, protons, alpha particles, and heavier atomic nuclei all together make up the corpuscular radiation of the Sun. A significant part of this radiation is a more or less continuous outflow of plasma - the solar wind, which is a continuation of the outer layers of the solar atmosphere - the solar corona. Against the background of this constantly blowing plasma wind, individual regions on the Sun are sources of more directed, enhanced, so-called corpuscular flows. Most likely, they are associated with special regions of the solar corona - coronary holes, and also, possibly, with long-lived active regions on the Sun. Finally, the most powerful short-term particle fluxes, mainly electrons and protons, are associated with solar flares. As a result of the most powerful flashes, particles can acquire velocities that make up a significant fraction of the speed of light. Particles with such high energies are called solar cosmic rays.

Solar corpuscular radiation has a strong influence on the Earth, and above all on the upper layers of its atmosphere and magnetic field, causing many geophysical phenomena. From harmful influence The radiation of the Sun protects us from the magnetosphere and the atmosphere of the Earth.

Solar radiation intensity

Having extremely high temperatures, the Sun is a very strong source of radiation. The visible range of solar radiation has the highest radiation intensity. At the same time, it also reaches the Earth a large number of invisible spectrum. Processes take place inside the Sun, in which helium atoms are synthesized from hydrogen atoms. These processes are called nuclear fusion processes, they are accompanied by the release huge amount energy. This energy leads to the fact that the Sun is heated to a temperature of 15 million degrees Celsius (in its inner part).

On the surface of the Sun (photosphere), the temperature reaches 5500 °C. On this surface, the Sun radiates energy with a value of 63 MW / m². Only a small part of this radiation reaches the surface of the Earth, which allows humanity to comfortably exist on our planet. The average intensity of radiation to the Earth's atmosphere is approximately equal to 1367 W/m². This value can fluctuate in the range of 5% due to the fact that, moving in an elliptical orbit, the Earth moves away from the Sun at different distances during the year. The value of 1367 W/m² is called the solar constant.

Solar energy on the Earth's surface

The Earth's atmosphere does not allow all solar energy to pass through. The Earth's surface reaches no more than 1000 W/m2. Part of the energy is absorbed, part is reflected in the layers of the atmosphere and in the clouds. A large amount of radiation is scattered in the layers of the atmosphere, resulting in the formation of scattered radiation (diffuse). On the Earth's surface, too, part of the radiation is reflected and becomes scattered. The sum of scattered and direct radiation is called total solar radiation. Scattered radiation can be from 20 to 60%.

The amount of energy reaching the Earth's surface is also affected by latitude and time of year. The axis of our planet, passing through the poles, is inclined by 23.5 ° relative to the orbit of rotation around the Sun. Between March

until September sunlight more falls on the Northern Hemisphere, the rest of the time - the Southern. Therefore, the length of the day in summer and winter time different. The latitude of the area affects the length of daylight hours. The further north, the longer summer time and vice versa.

Sun evolution

It is assumed that the Sun was born in a compressed gas and dust nebula. There are at least two theories as to what gave rise to the initial contraction of the nebula. According to one of them, it is assumed that one of the spiral arms of our galaxy passed through our region of space about 5 billion years ago. This could cause slight compression and lead to the formation of gravity centers in the gas-dust cloud. Indeed, now along the spiral arms we see a fairly large number of young stars and luminous gas clouds. Another theory suggests that somewhere nearby (on the scale of the universe, of course) an ancient massive supernova exploded. The resulting shock wave could be strong enough to initiate star formation in "our" gas-dust nebula. This theory is supported by the fact that scientists, studying meteorites, discovered quite a lot of elements that could be formed during a supernova explosion.

Further, when such a grandiose mass (2 * 1030 kg) was compressed under the influence of gravitational forces, it itself was strongly heated by internal pressure to temperatures at which thermonuclear reactions could begin in its center. In the central part, the temperature on the Sun is 15,000,000K, and the pressure reaches hundreds of billions of atmospheres. So a newborn star was lit (do not confuse with new stars).

Basically, the Sun at the beginning of its life consisted of hydrogen. It is hydrogen that in the course of thermonuclear reactions turns into helium, while the energy emitted by the Sun is released. The sun belongs to a type of star called a yellow dwarf. It is a main sequence star and belongs to the spectral type G2. The mass of a lone star quite unambiguously determines its fate. During its lifetime (~5 billion years), in the center of our star, where the temperature is quite high, about half of all the hydrogen available there burned out. Approximately the same, 5 billion years, the Sun has left to live in the form to which we are accustomed.

After hydrogen is running out in the center of the star, the Sun will increase in size and become a red giant. This will have a profound effect on the Earth: the temperature will rise, the oceans will boil away, life will become impossible. Then, having exhausted the "fuel" completely and no longer having the strength to hold the outer layers of the red giant, our star will end its life as a white dwarf, delighting extraterrestrial astronomers of the future unknown to us with a new planetary nebula, the shape of which may turn out to be very bizarre due to the influence of the planets.

Death of the Sun by Time

Already in 1.1 billion years, the star will increase its brightness by 10%, which will lead to a strong heating of the Earth.
After 3.5 billion years, the brightness will increase by 40%. The oceans will begin to evaporate and all life on Earth will end.
After 5.4 billion years, the core of the star will run out of fuel - hydrogen. The sun will begin to increase in size, due to the rarefaction of the outer shell and heating of the core.
After 7.7 billion years, our star will turn into a red giant, because. increase 200 times because of this, the planet Mercury will be absorbed.
At the end, after 7.9 billion years, the outer layers of the star will be so rarefied that they will disintegrate into a nebula, and in the center of the former Sun there will be a small object - a white dwarf. This is how our existence will end solar system. All building elements left after the collapse will not be lost, they will become the basis for the birth of new stars and planets.

The most common stars in the universe are red dwarfs. Much of this is due to their low mass, which allows them to live for a very long time before becoming white dwarfs.
Almost all stars in the universe have the same chemical composition and the reaction of nuclear fusion occurs in every star and is almost identical, determined only by the supply of fuel.
As we know, like a white dwarf, neutron stars are one of the final processes in the evolution of stars, largely arising after a supernova explosion. Previously, it was often difficult to distinguish a white dwarf from a neutron star, but now scientists using telescopes have found differences in them. A neutron star collects more light around it and this is easy to see with infrared telescopes. Eighth place among interesting facts about the stars.
Due to its incredible mass, according to general theory Einstein's relativity, a black hole is actually a bend in space, such that everything within their gravitational field is pushed towards it. The gravitational field of a black hole is so strong that even light cannot escape it.
As far as we know, when a star runs out of fuel, the star can grow in size by more than 1000 times, then it turns into a white dwarf, and because of the speed of the reaction, it explodes. This reaction is more commonly known as a supernova. Scientists suggest that in connection with this long process, such mysterious black holes are formed.
Many of the stars we see in the night sky can seem like a single glimmer of light. However, this is not always the case. Most of the stars we see in the sky are actually two star systems, or binary star systems. They are simply unimaginably far away and it seems to us that we see only one speck of light.
The stars that have the shortest lifespan are the most massive. They are a high mass chemical substances and tend to burn their fuel much faster.
Despite the fact that sometimes it seems to us that the Sun and stars twinkle, in fact it is not. The twinkling effect is just light from the star that is currently passing through the Earth's atmosphere but has not yet reached our eyes. Third place among the most interesting facts about the stars.
The distances involved in estimating how far to a star are unimaginably huge. Consider an example: The nearest star to the earth is at a distance of about 4.2 light years, and to get to it, even on our fastest ship, it will take about 70,000 years.
The coldest known star is the brown dwarf CFBDSIR 1458+10B, which has a temperature of only around 100°C. The hottest known star is a blue supergiant located in milky way called "Zeta Korma" its temperature is over 42,000 °C.

The most important source from which the surface of the Earth and the atmosphere receive thermal energy is the Sun. It sends a colossal amount of radiant energy into the world space: thermal, light, ultraviolet. emitted by the sun electromagnetic waves propagate at a speed of 300,000 km/s.

The heating of the earth's surface depends on the angle of incidence of the sun's rays. All the sun's rays hit the Earth's surface parallel to each other, but since the Earth has a spherical shape, the sun's rays fall on different parts of its surface at different angles. When the Sun is at its zenith, its rays fall vertically and the Earth heats up more.

The totality of radiant energy sent by the Sun is called solar radiation, it is usually expressed in calories per surface area per year.

Solar radiation determines temperature regime Earth's air troposphere.

It should be noted that total solar radiation is more than two billion times the amount of energy received by the Earth.

Radiation reaching the earth's surface consists of direct and diffuse.

Radiation that comes to Earth directly from the Sun in the form of direct sunlight in a cloudless sky is called straight. It carries the greatest amount of heat and light. If our planet had no atmosphere, the earth's surface would receive only direct radiation.

However, passing through the atmosphere, about a quarter of the solar radiation is scattered by gas molecules and impurities, deviates from the direct path. Some of them reach the Earth's surface, forming scattered solar radiation. Thanks to scattered radiation, light also penetrates into places where direct sunlight (direct radiation) does not penetrate. This radiation creates daylight and gives color to the sky.

Total solar radiation

All the rays of the sun that hit the earth are total solar radiation i.e., the totality of direct and diffuse radiation (Fig. 1).

Rice. 1. Total solar radiation per year

Distribution of solar radiation over the earth's surface

Solar radiation is distributed unevenly over the earth. It depends:

1. on the density and humidity of the air - the higher they are, the less radiation the earth's surface receives;

2. from geographical latitude terrain - the amount of radiation increases from the poles to the equator. The amount of direct solar radiation depends on the length of the path that the sun's rays travel through the atmosphere. When the Sun is at its zenith (the angle of incidence of the rays is 90 °), its rays fall on the Earth the shortest way and intensively give their energy to a small area. On Earth, this occurs in the band between 23° N. sh. and 23°S sh., i.e. between the tropics. As you move away from this zone to the south or north, the length of the path of the sun's rays increases, i.e., the angle of their incidence on the earth's surface decreases. The rays begin to fall on the Earth at a smaller angle, as if gliding, approaching the tangent line in the region of the poles. As a result, the same energy flow is distributed to large area, so the amount of reflected energy increases. Thus, in the region of the equator, where the sun's rays fall on the earth's surface at an angle of 90 °, the amount of direct solar radiation received by the earth's surface is higher, and as you move towards the poles, this amount is sharply reduced. In addition, the length of the day depends on the latitude of the area. different times year, which also determines the amount of solar radiation entering the earth's surface;

3. from the annual and daily movement of the Earth - in the middle and high latitudes, the influx of solar radiation varies greatly according to the seasons, which is associated with a change in the noon height of the Sun and the length of the day;

4. on the nature of the earth's surface - the brighter the surface, the more sunlight it reflects. The ability of a surface to reflect radiation is called albedo(from lat. whiteness). Snow reflects radiation especially strongly (90%), sand is weaker (35%), chernozem is even weaker (4%).

Earth's surface, absorbing solar radiation (absorbed radiation), heats up and radiates heat into the atmosphere (reflected radiation). The lower layers of the atmosphere largely delay terrestrial radiation. The radiation absorbed by the earth's surface is spent on heating the soil, air, and water.

That part of the total radiation that remains after reflection and thermal radiation of the earth's surface is called radiation balance. The radiation balance of the earth's surface varies during the day and seasons of the year, but on average for the year it has positive value everywhere except icy deserts Greenland and Antarctica. Maximum values radiation balance reaches at low latitudes (between 20 ° N and 20 ° S) - over 42 * 10 2 J / m 2, at a latitude of about 60 ° in both hemispheres it decreases to 8 * 10 2 -13 * 10 2 J / m 2.

The sun's rays give up to 20% of their energy to the atmosphere, which is distributed throughout the entire thickness of the air, and therefore the heating of the air caused by them is relatively small. The sun heats the earth's surface, which transfers heat atmospheric air at the expense convection(from lat. convection- delivery), i.e., the vertical movement of air heated at the earth's surface, in place of which colder air descends. That's how the atmosphere gets most heat - on average three times more than directly from the Sun.

Presence in carbon dioxide and water vapor does not allow the heat reflected from the earth's surface to freely escape into outer space. They create Greenhouse effect, due to which the temperature drop on Earth during the day does not exceed 15 ° C. In the absence of carbon dioxide in the atmosphere, the earth's surface would cool down by 40-50 °C overnight.

As a result of scale growth economic activity people - burning coal and oil at thermal power plants, emissions from industrial enterprises, an increase in car emissions - the content of carbon dioxide in the atmosphere rises, which leads to increased greenhouse effect and threatens global change climate.

The sun's rays, having passed through the atmosphere, fall on the surface of the Earth and heat it, and that, in turn, gives off heat to the atmosphere. This explains salient feature troposphere: decrease in air temperature with height. But there are times when the upper layers of the atmosphere are warmer than the lower ones. Such a phenomenon is called temperature inversion(from lat. inversio - turning over).

Heat sources. In the life of the atmosphere is crucial thermal energy. The main source of this energy is the Sun. As for the thermal radiation of the Moon, planets and stars, it is so negligible for the Earth that in practice it cannot be taken into account. Much more thermal energy is provided by the internal heat of the Earth. According to the calculations of geophysicists, a constant influx of heat from the bowels of the Earth increases the temperature of the earth's surface by 0.1. But such an influx of heat is still so small that there is no need to take it into account either. Thus, only the Sun can be considered the only source of thermal energy on the Earth's surface.

Solar radiation. The sun, which has a temperature of the photosphere (radiating surface) of about 6000°, radiates energy into space in all directions. Part of this energy in the form of a huge beam of parallel solar rays hits the Earth. Solar energy that reaches the earth's surface in the form of direct rays from the sun is called direct solar radiation. But not all solar radiation directed to the Earth reaches the earth's surface, since the sun's rays, passing through a powerful layer of the atmosphere, are partially absorbed by it, partially scattered by molecules and suspended particles of air, some of it is reflected by clouds. That part solar energy that dissipates in the atmosphere is called scattered radiation. Scattered solar radiation propagates in the atmosphere and reaches the Earth's surface. We perceive this type of radiation as uniform daylight, when the Sun is completely covered by clouds or has just disappeared below the horizon.

Direct and diffuse solar radiation, reaching the Earth's surface, is not completely absorbed by it. Part of the solar radiation is reflected from the earth's surface back into the atmosphere and is there in the form of a stream of rays, the so-called reflected solar radiation.

The composition of solar radiation is very complex, which is associated with a very high temperature radiating surface of the sun. Conventionally, according to the wavelength, the spectrum of solar radiation is divided into three parts: ultraviolet (η<0,4<μ видимую глазом (η from 0.4μ to 0.76μ) and infrared (η >0.76μ). In addition to the temperature of the solar photosphere, the composition of solar radiation near the earth's surface is also influenced by the absorption and scattering of part of the sun's rays as they pass through the air envelope of the Earth. In this regard, the composition of solar radiation at the upper boundary of the atmosphere and near the Earth's surface will be different. Based on theoretical calculations and observations, it has been established that at the boundary of the atmosphere, ultraviolet radiation accounts for 5%, visible rays - 52% and infrared - 43%. At the earth's surface (at a Sun height of 40 °), ultraviolet rays make up only 1%, visible - 40%, and infrared - 59%.

Intensity of solar radiation. Under the intensity of direct solar radiation understand the amount of heat in calories received in 1 minute. from the radiant energy of the Sun by the surface in 1 cm 2, placed perpendicular to the sun.

To measure the intensity of direct solar radiation, special instruments are used - actinometers and pyrheliometers; the amount of scattered radiation is determined by a pyranometer. Automatic recording of the duration of solar radiation action is carried out by actinographs and heliographs. The spectral intensity of solar radiation is determined by a spectrobolograph.

At the boundary of the atmosphere, where the absorbing and scattering effects of the Earth's air envelope are excluded, the intensity of direct solar radiation is approximately 2 feces for 1 cm 2 surfaces in 1 min. This value is called solar constant. The intensity of solar radiation in 2 feces for 1 cm 2 in 1 min. gives such a large amount of heat during the year that it would be enough to melt a layer of ice 35 m thick, if such a layer covered the entire earth's surface.

Numerous measurements of the intensity of solar radiation give reason to believe that the amount of solar energy coming to the upper boundary of the Earth's atmosphere experiences fluctuations in the amount of several percent. Oscillations are periodic and non-periodic, apparently associated with the processes occurring on the Sun itself.

In addition, some change in the intensity of solar radiation occurs during the year due to the fact that the Earth in its annual rotation does not move in a circle, but in an ellipse, in one of the foci of which is the Sun. In this regard, the distance from the Earth to the Sun changes and, consequently, there is a fluctuation in the intensity of solar radiation. The greatest intensity is observed around January 3, when the Earth is closest to the Sun, and the smallest around July 5, when the Earth is at its maximum distance from the Sun.

For this reason, the fluctuation in the intensity of solar radiation is very small and can only be of theoretical interest. (The amount of energy at maximum distance is related to the amount of energy at minimum distance, as 100:107, i.e. the difference is completely negligible.)

Conditions for irradiation of the surface of the globe. Already the spherical shape of the Earth alone leads to the fact that the radiant energy of the Sun is distributed very unevenly on the earth's surface. So, on the days of the spring and autumn equinoxes (March 21 and September 23), only at the equator at noon, the angle of incidence of the rays will be 90 ° (Fig. 30), and as it approaches the poles, it will decrease from 90 to 0 °. In this way,

if at the equator the amount of radiation received is taken as 1, then at the 60th parallel it will be expressed as 0.5, and at the pole it will be equal to 0.

The globe, in addition, has a daily and annual movement, and the earth's axis is inclined to the plane of the orbit by 66 °.5. Due to this inclination, an angle of 23 ° 30 g is formed between the plane of the equator and the plane of the orbit. This circumstance leads to the fact that the angles of incidence of the sun's rays for the same latitudes will vary within 47 ° (23.5 + 23.5) .

Depending on the time of year, not only the angle of incidence of the rays changes, but also the duration of illumination. If in tropical countries at all times of the year the duration of day and night is approximately the same, then in polar countries, on the contrary, it is very different. For example, at 70° N. sh. in summer, the Sun does not set for 65 days, at 80 ° N. sh.- 134, and at the pole -186. Because of this, at the North Pole, radiation on the day of the summer solstice (June 22) is 36% more than at the equator. As for the entire summer half-year, the total amount of heat and light received by the pole is only 17% less than at the equator. Thus, in the summertime in polar countries, the duration of illumination largely compensates for the lack of radiation, which is a consequence of the small angle of incidence of the rays. In the winter half of the year, the picture is completely different: the amount of radiation at the same North Pole will be 0. As a result, the average amount of radiation at the pole is 2.4 times less than at the equator. From all that has been said, it follows that the amount of solar energy that the Earth receives by radiation is determined by the angle of incidence of the rays and the duration of exposure.

In the absence of an atmosphere at different latitudes, the earth's surface would receive the following amount of heat per day, expressed in calories per 1 cm 2(see table on page 92).

The distribution of radiation over the earth's surface given in the table is commonly called solar climate. We repeat that we have such a distribution of radiation only at the upper boundary of the atmosphere.

Attenuation of solar radiation in the atmosphere. So far, we have been talking about the conditions for the distribution of solar heat over the earth's surface, without taking into account the atmosphere. Meanwhile, the atmosphere in this case is of great importance. Solar radiation, passing through the atmosphere, experiences dispersion and, in addition, absorption. Both of these processes together attenuate solar radiation to a large extent.

The sun's rays, passing through the atmosphere, first of all experience scattering (diffusion). Scattering is created by the fact that the rays of light, refracting and reflecting from air molecules and particles of solid and liquid bodies in the air, deviate from the direct path to really "spread out".

Scattering greatly attenuates solar radiation. With an increase in the amount of water vapor and especially dust particles, the dispersion increases and the radiation is weakened. In large cities and desert areas, where the dust content of the air is greatest, dispersion weakens the strength of radiation by 30-45%. Thanks to scattering, the daylight is obtained, which illuminates objects, even if the sun's rays do not fall directly on them. Scattering determines the very color of the sky.

Let us now dwell on the ability of the atmosphere to absorb the radiant energy of the Sun. The main gases that make up the atmosphere absorb radiant energy relatively very little. Impurities (water vapor, ozone, carbon dioxide and dust), on the contrary, are distinguished by a high absorption capacity.

In the troposphere, the most significant admixture is water vapor. They absorb especially strongly infrared (long-wave), i.e., predominantly thermal rays. And the more water vapor in the atmosphere, the naturally more and. absorption. The amount of water vapor in the atmosphere is subject to large changes. Under natural conditions, it varies from 0.01 to 4% (by volume).

Ozone is very absorbent. A significant admixture of ozone, as already mentioned, is in the lower layers of the stratosphere (above the tropopause). Ozone absorbs ultraviolet (shortwave) rays almost completely.

Carbon dioxide is also very absorbent. It absorbs mainly long-wave, i.e., predominantly thermal rays.

Dust in the air also absorbs some of the sun's radiation. Heating up under the action of sunlight, it can significantly increase the temperature of the air.

Of the total amount of solar energy coming to Earth, the atmosphere absorbs only about 15%.

The attenuation of solar radiation by scattering and absorption by the atmosphere is very different for different latitudes of the Earth. This difference depends primarily on the angle of incidence of the rays. At the zenith position of the Sun, the rays, falling vertically, cross the atmosphere in the shortest way. As the angle of incidence decreases, the path of the rays lengthens and the attenuation of solar radiation becomes more significant. The latter is clearly seen from the drawing (Fig. 31) and the attached table (in the table, the path of the sun's beam at the zenith position of the Sun is taken as unity).

Depending on the angle of incidence of the rays, not only the number of rays changes, but also their quality. During the period when the Sun is at its zenith (overhead), ultraviolet rays account for 4%,

visible - 44% and infrared - 52%. At the position of the Sun, there are no ultraviolet rays at all at the horizon, visible 28% and infrared 72%.

The complexity of the influence of the atmosphere on solar radiation is aggravated by the fact that its transmission capacity varies greatly depending on the time of year and weather conditions. So, if the sky remained cloudless all the time, then the annual course of the influx of solar radiation at different latitudes could be graphically expressed as follows (Fig. 32) It is clearly seen from the drawing that with a cloudless sky in Moscow in May, June and July solar radiation would produce more than at the equator. Similarly, in the second half of May, in June and the first half of July, more heat would be generated at the North Pole than at the equator and in Moscow. We repeat that this would be the case with a cloudless sky. But in fact, this does not work, because cloud cover significantly weakens solar radiation. Let us give an example shown in the graph (Fig. 33). The graph shows how much solar radiation does not reach the Earth's surface: a significant part of it is retained by the atmosphere and clouds.

However, it must be said that the heat absorbed by the clouds partly goes to warm the atmosphere, and partly indirectly reaches the earth's surface.

The daily and annual course of the intensity of solnight radiation. The intensity of direct solar radiation near the Earth's surface depends on the height of the Sun above the horizon and on the state of the atmosphere (on its dustiness). If. the transparency of the atmosphere during the day was constant, then the maximum intensity of solar radiation would be observed at noon, and the minimum - at sunrise and sunset. In this case, the graph of the course of the daily intensity of solar radiation would be symmetrical with respect to half a day.

The content of dust, water vapor and other impurities in the atmosphere is constantly changing. In this regard, the transparency of the air changes and the symmetry of the graph of the course of the intensity of solar radiation is violated. Often, especially in the summer, at midday, when the earth's surface is heated intensely, powerful ascending air currents occur, and the amount of water vapor and dust in the atmosphere increases. This leads to a significant decrease in solar radiation at noon; the maximum intensity of radiation in this case is observed in the pre-noon or afternoon hours. The annual course of the intensity of solar radiation is also associated with changes in the height of the Sun above the horizon during the year and with the state of transparency of the atmosphere in different seasons. In the countries of the northern hemisphere, the greatest height of the Sun above the horizon occurs in the month of June. But at the same time, the greatest dustiness of the atmosphere is also observed. Therefore, the maximum intensity usually occurs not in the middle of summer, but in the spring months, when the Sun rises quite high * above the horizon, and the atmosphere after winter remains relatively clean. To illustrate the annual course of the solar radiation intensity in the northern hemisphere, we present data on the average monthly midday values of the radiation intensity in Pavlovsk.

The amount of heat from solar radiation. The surface of the Earth during the day continuously receives heat from direct and diffuse solar radiation or only from diffuse radiation (in cloudy weather). The daily value of heat is determined on the basis of actinometric observations: by taking into account the amount of direct and diffuse radiation that has entered the earth's surface. Having determined the amount of heat for each day, the amount of heat received by the earth's surface per month or per year is also calculated.

The daily amount of heat received by the earth's surface from solar radiation depends on the intensity of radiation and on the duration of its action during the day. In this regard, the minimum influx of heat occurs in the winter, and the maximum in the summer. In the geographic distribution of total radiation over the globe, its increase is observed with a decrease in the latitude of the area. This position is confirmed by the following table.

The role of direct and diffuse radiation in the annual amount of heat received by the earth's surface at different latitudes of the globe is not the same. At high latitudes, diffuse radiation predominates in the annual heat sum. With a decrease in latitude, the predominant value passes to direct solar radiation. So, for example, in the Tikhaya Bay, diffuse solar radiation provides 70% of the annual amount of heat, and direct radiation only 30%. In Tashkent, on the contrary, direct solar radiation gives 70%, diffused only 30%.

Reflectivity of the Earth. Albedo. As already mentioned, the Earth's surface absorbs only part of the solar energy coming to it in the form of direct and diffuse radiation. The other part is reflected into the atmosphere. The ratio of the amount of solar radiation reflected by a given surface to the amount of radiant energy flux incident on this surface is called albedo. Albedo is expressed as a percentage and characterizes the reflectivity of a given area of the surface.

Albedo depends on the nature of the surface (properties of the soil, the presence of snow, vegetation, water, etc.) and on the angle of incidence of the Sun's rays on the Earth's surface. So, for example, if the rays fall on the earth's surface at an angle of 45 °, then:

From the above examples, it can be seen that the reflectivity of various objects is not the same. It is most near snow and least near water. However, the examples we have taken refer only to those cases where the height of the Sun above the horizon is 45°. As this angle decreases, the reflectivity increases. So, for example, at a height of the Sun at 90 °, water reflects only 2%, at 50 ° - 4%, at 20 ° -12%, at 5 ° - 35-70% (depending on the state of the water surface).

On average, with a cloudless sky, the surface of the globe reflects 8% of solar radiation. In addition, 9% reflects the atmosphere. Thus, the globe as a whole, with a cloudless sky, reflects 17% of the radiant energy of the Sun falling on it. If the sky is covered with clouds, then 78% of the radiation is reflected from them. If we take natural conditions, based on the ratio between a cloudless sky and a sky covered with clouds, which is observed in reality, then the reflectivity of the Earth as a whole is 43%.

Terrestrial and atmospheric radiation. The earth, receiving solar energy, heats up and itself becomes a source of heat radiation into the world space. However, the rays emitted by the earth's surface differ sharply from the sun's rays. The earth emits only long-wave (λ 8-14 μ) invisible infrared (thermal) rays. The energy emitted by the earth's surface is called earth radiation. Earth radiation occurs and. day and night. The intensity of the radiation is greater, the higher the temperature of the radiating body. Terrestrial radiation is determined in the same units as solar radiation, i.e., in calories from 1 cm 2 surfaces in 1 min. Observations have shown that the magnitude of terrestrial radiation is small. Usually it reaches 15-18 hundredths of a calorie. But, acting continuously, it can give a significant thermal effect.

The strongest terrestrial radiation is obtained with a cloudless sky and good transparency of the atmosphere. Cloudiness (especially low clouds) significantly reduces terrestrial radiation and often brings it to zero. Here we can say that the atmosphere, together with the clouds, is a good "blanket" that protects the Earth from excessive cooling. Parts of the atmosphere, like areas of the earth's surface, radiate energy according to their temperature. This energy is called atmospheric radiation. The intensity of atmospheric radiation depends on the temperature of the radiating part of the atmosphere, as well as on the amount of water vapor and carbon dioxide contained in the air. Atmospheric radiation belongs to the group of long-wave radiation. It spreads in the atmosphere in all directions; some of it reaches the earth's surface and is absorbed by it, the other part goes into interplanetary space.

O income and expenditure of solar energy on Earth. The earth's surface, on the one hand, receives solar energy in the form of direct and diffuse radiation, and on the other hand, loses part of this energy in the form of terrestrial radiation. As a result of the arrival and consumption of solar "energy, some result is obtained. In some cases, this result can be positive, in others negative. Let's give examples of both.

January 8. The day is cloudless. For 1 cm 2 the earth's surface received per day 20 feces direct solar radiation and 12 feces scattered radiation; in total, thus received 32 cal. During the same time, due to radiation 1 cm? earth surface lost 202 cal. As a result, in the language of accounting, there is a loss of 170 feces(negative balance).

July 6th The sky is almost cloudless. 630 received from direct solar radiation cal, from scattered radiation 46 cal. In total, therefore, the earth's surface received 1 cm 2 676 cal. 173 lost by terrestrial radiation cal. In the balance sheet profit on 503 feces(balance positive).

From the above examples, among other things, it is quite clear why in temperate latitudes it is cold in winter and warm in summer.

The use of solar radiation for technical and domestic purposes. Solar radiation is an inexhaustible natural source of energy. The magnitude of solar energy on Earth can be judged by the following example: if, for example, we use the heat of solar radiation, which falls on only 1/10 of the area of the USSR, then we can get energy equal to the work of 30 thousand Dneproges.

People have long sought to use the free energy of solar radiation for their needs. To date, many different solar installations have been created that operate on the use of solar radiation and are widely used in industry and to meet the household needs of the population. In the southern regions of the USSR, solar water heaters, boilers, salt water desalination plants, solar dryers (for drying fruits), kitchens, bathhouses, greenhouses, and apparatus for medical purposes operate on the basis of the widespread use of solar radiation in industry and public utilities. Solar radiation is widely used in resorts for the treatment and promotion of people's health.

The visible part of solar radiation, when studied with the help of spectrum-analyzing instruments, turns out to be inhomogeneous - absorption lines are observed in the spectrum, first described by J. Fraunhofer in 1814. These lines arise when photons of certain wavelengths are absorbed by atoms of various chemical elements in the upper, relatively cold, layers of the Sun's atmosphere. Spectral analysis makes it possible to obtain information about the composition of the Sun, since a certain set of spectral lines characterizes a chemical element extremely accurately. So, for example, with the help of observations of the spectrum of the Sun, the discovery of helium was predicted, which was isolated on Earth later.

X-rays come mainly from the upper layers of the chromosphere and the corona. The radiation is especially strong during the years of maximum solar activity.

The sun emits not only light, heat and all other types of electromagnetic radiation. It is also a source of a constant flow of particles - corpuscles. Neutrinos, electrons, protons, alpha particles, and heavier atomic nuclei all together make up the corpuscular radiation of the Sun. A significant part of this radiation is a more or less continuous outflow of plasma - the solar wind, which is a continuation of the outer layers of the solar atmosphere - the solar corona. Against the background of this constantly blowing plasma wind, individual regions on the Sun are sources of more directed, enhanced, so-called corpuscular flows. Most likely, they are associated with special regions of the solar corona - coronary holes, and also, possibly, with long-lived active regions on the Sun. Finally, the most powerful short-term particle fluxes, mainly electrons and protons, are associated with solar flares. As a result of the most powerful flashes, particles can acquire velocities that make up a significant fraction of the speed of light. Particles with such high energies are called solar cosmic rays.

Solar corpuscular radiation has a strong influence on the Earth, and above all on the upper layers of its atmosphere and magnetic field, causing many geophysical phenomena. The magnetosphere and the Earth's atmosphere protect us from the harmful effects of solar radiation.