How many layers of the earth's atmosphere. The role and importance of the main gases of atmospheric air

garden equipment 13.10.2019

garden equipment

– air envelope the globe rotating with the earth. The upper boundary of the atmosphere is conventionally carried out at altitudes of 150-200 km. The lower boundary is the surface of the Earth.

Atmospheric air is a mixture of gases. Most of its volume in the surface air layer is nitrogen (78%) and oxygen (21%). In addition, the air contains inert gases (argon, helium, neon, etc.), carbon dioxide (0.03), water vapor, and various solid particles (dust, soot, salt crystals).

The air is colorless, and the color of the sky is explained by the peculiarities of the scattering of light waves.

The atmosphere consists of several layers: troposphere, stratosphere, mesosphere and thermosphere.

The bottom layer of air is called troposphere. At different latitudes, its power is not the same. The troposphere repeats the shape of the planet and participates together with the Earth in axial rotation. At the equator, the thickness of the atmosphere varies from 10 to 20 km. At the equator it is greater, and at the poles it is less. The troposphere is characterized by the maximum density of air, 4/5 of the mass of the entire atmosphere is concentrated in it. The troposphere determines weather: various air masses are formed here, clouds and precipitation are formed, there is an intensive horizontal and vertical movement of air.

Above the troposphere, up to an altitude of 50 km, is located stratosphere. It is characterized by a lower density of air, there is no water vapor in it. In the lower part of the stratosphere at altitudes of about 25 km. there is an "ozone screen" - a layer of the atmosphere with a high concentration of ozone, which absorbs ultraviolet radiation, which is fatal to organisms.

At an altitude of 50 to 80-90 km extends mesosphere. As the altitude increases, the temperature decreases with an average vertical gradient of (0.25-0.3)° / 100 m, and the air density decreases. The main energy process is radiant heat transfer. Atmospheric glow due to complex photo chemical processes with the participation of radicals, vibrationally excited molecules.

Thermosphere located at an altitude of 80-90 to 800 km. The air density here is minimal, the degree of air ionization is very high. The temperature changes depending on the activity of the Sun. Due to the large number of charged particles, auroras and magnetic storms are observed here.

The atmosphere is of great importance for the nature of the Earth. Without oxygen, living organisms cannot breathe. Its ozone layer protects all living things from harmful ultraviolet rays. The atmosphere smooths out temperature fluctuations: the Earth's surface does not get supercooled at night and does not overheat during the day. In dense layers of atmospheric air, not reaching the surface of the planet, meteorites burn out from thorns.

The atmosphere interacts with all the shells of the earth. With its help, the exchange of heat and moisture between the ocean and land. Without the atmosphere there would be no clouds, precipitation, winds.

Human activities have a significant adverse effect on the atmosphere. Air pollution occurs, which leads to an increase in the concentration of carbon monoxide (CO 2). And this contributes to global warming and enhances the "greenhouse effect". The ozone layer of the Earth is being destroyed due to industrial waste and transport.

The atmosphere needs to be protected. In developed countries, a set of measures is being taken to protect atmospheric air from pollution.

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Blue planet...

This topic was supposed to appear on the site one of the first. After all, helicopters are atmospheric aircraft. Earth's atmosphere- their, so to speak, habitat :-). A physical properties of air just determine the quality of this habitat :-). So that's one of the basics. And the basis is always written first. But I just realized this now. However, it is better, as you know, late than never ... Let's touch on this issue, but without getting into the wilds and unnecessary difficulties :-).

So… Earth's atmosphere. This is the gaseous shell of our blue planet. Everyone knows this name. Why blue? Simply because the "blue" (as well as blue and violet) component of sunlight (spectrum) is most well scattered in the atmosphere, thus coloring it in bluish-bluish, sometimes with a hint of violet (on a sunny day, of course :-)) .

Composition of the Earth's atmosphere.

The composition of the atmosphere is quite wide. I will not list all the components in the text, there is a good illustration for this. The composition of all these gases is almost constant, with the exception of carbon dioxide (CO 2 ). In addition, the atmosphere necessarily contains water in the form of vapors, suspended droplets or ice crystals. The amount of water is not constant and depends on temperature and, to a lesser extent, on air pressure. In addition, the Earth's atmosphere (especially the current one) also contains a certain amount, I would say "all sorts of filth" :-). These are SO 2, NH 3, CO, HCl, NO, in addition there are mercury vapors Hg. True, all this is there in small quantities, thank God :-).

Earth's atmosphere divided into several following friend one after the other in height above the surface of the zones.

The first, closest to the earth, is the troposphere. This is the lowest and, so to speak, the main layer for the life of various types. It contains 80% of the mass of all atmospheric air (although by volume it makes up only about 1% of the entire atmosphere) and about 90% of all atmospheric water. The bulk of all winds, clouds, rains and snows 🙂 come from there. The troposphere extends to heights of about 18 km in tropical latitudes and up to 10 km in polar latitudes. The air temperature in it drops with a rise of about 0.65º for every 100 m.

atmospheric zones.

The second zone is the stratosphere. I must say that another narrow zone is distinguished between the troposphere and stratosphere - the tropopause. It stops the temperature drop with height. The tropopause has an average thickness of 1.5-2 km, but its boundaries are indistinct and the troposphere often overlaps the stratosphere.

So the stratosphere has an average height of 12 km to 50 km. The temperature in it up to 25 km remains unchanged (about -57ºС), then somewhere up to 40 km it rises to about 0ºС and further up to 50 km it remains unchanged. The stratosphere is a relatively quiet part of the earth's atmosphere. There are practically no adverse weather conditions in it. It is in the stratosphere that the famous ozone layer is located at altitudes from 15-20 km to 55-60 km.

This is followed by a small boundary layer stratopause, where the temperature remains around 0ºС, and then the next zone is the mesosphere. It extends to altitudes of 80-90 km, and in it the temperature drops to about 80ºС. In the mesosphere, small meteors usually become visible, which begin to glow in it and burn out there.

The next narrow gap is the mesopause and beyond it the thermosphere zone. Its height is up to 700-800 km. Here the temperature again begins to rise and at altitudes of about 300 km it can reach values of the order of 1200ºС. Thereafter, it remains constant. The ionosphere is located inside the thermosphere up to a height of about 400 km. Here, the air is strongly ionized due to exposure to solar radiation and has a high electrical conductivity.

The next and, in general, the last zone is the exosphere. This is the so-called scatter zone. Here, mainly very rarefied hydrogen and helium (with a predominance of hydrogen) are present. At altitudes of about 3000 km, the exosphere passes into the near space vacuum.

It's like that somewhere. Why about? Because these layers are rather conditional. Various changes in altitude, composition of gases, water, temperature, ionization, and so on are possible. In addition, there are many more terms that define the structure and state of the earth's atmosphere.

For example homosphere and heterosphere. In the first, the atmospheric gases are well mixed and their composition is quite homogeneous. The second is located above the first and there is practically no such mixing there. The gases are separated by gravity. The boundary between these layers is located at an altitude of 120 km, and it is called turbopause.

Perhaps we will finish with the terms, but I will definitely add that it is conventionally assumed that the boundary of the atmosphere is located at an altitude of 100 km above sea level. This border is called the Karman Line.

I will add two more pictures to illustrate the structure of the atmosphere. The first, however, is in German, but it is complete and easy enough to understand :-). It can be enlarged and well considered. The second shows the change in atmospheric temperature with altitude.

The structure of the Earth's atmosphere.

Change in air temperature with altitude.

Modern manned orbital spacecraft fly at altitudes of about 300-400 km. However, this is no longer aviation, although the area, of course, is in a certain sense closely related, and we will definitely talk about it again :-).

The aviation zone is the troposphere. Modern atmospheric aircraft can also fly in the lower layers of the stratosphere. For example, the practical ceiling of the MIG-25RB is 23000 m.

Flight in the stratosphere.

And exactly physical properties of air tropospheres determine how the flight will be, how effective the aircraft control system will be, how turbulence in the atmosphere will affect it, how the engines will work.

The first main property is air temperature. In gas dynamics, it can be determined on the Celsius scale or on the Kelvin scale.

Temperature t1 at a given height H on the Celsius scale is determined:

t 1 \u003d t - 6.5N, where t is the air temperature at the ground.

Temperature on the Kelvin scale is called absolute temperature Zero on this scale is absolute zero. At absolute zero, the thermal motion of molecules stops. Absolute zero on the Kelvin scale corresponds to -273º on the Celsius scale.

Accordingly, the temperature T on high H on the Kelvin scale is determined:

T \u003d 273K + t - 6.5H

Air pressure. Atmospheric pressure is measured in Pascals (N / m 2), in the old system of measurement in atmospheres (atm.). There is also such a thing as barometric pressure. This is the pressure measured in millimeters of mercury using a mercury barometer. Barometric pressure (pressure at sea level) equal to 760 mm Hg. Art. called standard. In physics, 1 atm. just equal to 760 mm Hg.

Air density. In aerodynamics, the most commonly used concept is the mass density of air. This is the mass of air in 1 m3 of volume. The density of air changes with height, the air becomes more rarefied.

Air humidity. Shows the amount of water in the air. There is a concept " relative humidity". This is the ratio of the mass of water vapor to the maximum possible at a given temperature. The concept of 0%, that is, when the air is completely dry, can exist in general only in the laboratory. On the other hand, 100% humidity is quite real. This means that the air has absorbed all the water it could absorb. Something like an absolutely "full sponge". High relative humidity reduces air density, while low relative humidity increases it accordingly.

Due to the fact that aircraft flights take place under different atmospheric conditions, their flight and aerodynamic parameters in one flight mode may be different. Therefore, for a correct assessment of these parameters, we introduced International Standard Atmosphere (ISA). It shows the change in the state of the air with the rise in altitude.

The main parameters of the state of air at zero humidity are taken as:

pressure P = 760 mm Hg. Art. (101.3 kPa);

temperature t = +15°C (288 K);

mass density ρ \u003d 1.225 kg / m 3;

For the ISA, it is assumed (as mentioned above :-)) that the temperature drops in the troposphere by 0.65º for every 100 meters of altitude.

Standard atmosphere (example up to 10000 m).

ISA tables are used for calibrating instruments, as well as for navigational and engineering calculations.

Physical properties of air also include such concepts as inertness, viscosity and compressibility.

Inertia is a property of air that characterizes its ability to resist a change in the state of rest or uniform rectilinear motion. . The measure of inertia is the mass density of air. The higher it is, the higher the inertia and drag force of the medium when the aircraft moves in it.

Viscosity. Determines the frictional resistance against air as the aircraft moves.

Compressibility measures the change in air density as pressure changes. At low speeds of the aircraft (up to 450 km/h), there is no change in pressure when the air flow flows around it, but at high speeds, the effect of compressibility begins to appear. Its influence on supersonic is especially pronounced. This is a separate area of aerodynamics and a topic for a separate article :-).

Well, it seems that's all for now ... It's time to finish this slightly tedious enumeration, which, however, cannot be dispensed with :-). Earth's atmosphere, its parameters, physical properties of air are as important for the aircraft as the parameters of the apparatus itself, and it was impossible not to mention them.

For now, until the next meetings and more interesting topics 🙂 …

P.S. For dessert, I suggest watching a video filmed from the cockpit of a MIG-25PU twin during its flight into the stratosphere. Filmed, apparently, by a tourist who has money for such flights :-). Filmed mostly through the windshield. Notice the color of the sky...

Encyclopedic YouTube

1 / 5

✪ Earth spaceship (Episode 14) - Atmosphere

✪ Why wasn't the atmosphere pulled into the vacuum of space?

✪ Entry into the Earth's atmosphere of the spacecraft "Soyuz TMA-8"

✪ Atmosphere structure, meaning, study

✪ O. S. Ugolnikov "Upper atmosphere. Meeting of the Earth and space"

Subtitles

Atmosphere boundary

The atmosphere is considered to be that area around the Earth in which gaseous environment rotates together with the Earth as a whole. The atmosphere passes into interplanetary space gradually, in the exosphere, starting at an altitude of 500-1000 km from the Earth's surface.

According to the definition proposed by the International Aviation Federation, the boundary between the atmosphere and space is drawn along the Karmana line, located at an altitude of about 100 km, above which air flights become completely impossible. NASA uses the 122 kilometers (400,000 feet) mark as the boundary of the atmosphere, where the shuttles switch from powered maneuvering to aerodynamic maneuvering.

Physical Properties

In addition to the gases indicated in the table, the atmosphere contains Cl 2, SO 2, NH 3, CO, O 3, NO 2, hydrocarbons, HCl,, HBr, vapors, I 2, Br 2, as well as many other gases in minor quantities. In the troposphere there is constantly a large amount of suspended solid and liquid particles (aerosol). Radon (Rn) is the rarest gas in the Earth's atmosphere.

The structure of the atmosphere

boundary layer of the atmosphere

The lower layer of the troposphere (1-2 km thick), in which the state and properties of the Earth's surface directly affect the dynamics of the atmosphere.

Troposphere

Its upper limit is at an altitude of 8-10 km in polar, 10-12 km in temperate and 16-18 km in tropical latitudes; lower in winter than in summer.
The lower, main layer of the atmosphere contains more than 80% of the total mass of atmospheric air and about 90% of all water vapor present in the atmosphere. Turbulence and convection are strongly developed in the troposphere, clouds appear, cyclones and anticyclones develop. Temperature decreases with altitude with an average vertical gradient of 0.65°/100 meters.

tropopause

The transitional layer from the troposphere to the stratosphere, the layer of the atmosphere in which the decrease in temperature with height stops.

Stratosphere

The layer of the atmosphere located at an altitude of 11 to 50 km. A slight change in temperature in the 11-25 km layer (the lower layer of the stratosphere) and its increase in the 25-40 km layer from −56.5 to +0.8 ° (upper stratosphere or inversion region) are typical. Having reached a value of about 273 K (almost 0 °C) at an altitude of about 40 km, the temperature remains constant up to an altitude of about 55 km. This region of constant temperature is called the stratopause and is the boundary between the stratosphere and the mesosphere.

Stratopause

The boundary layer of the atmosphere between the stratosphere and the mesosphere. There is a maximum in the vertical temperature distribution (about 0 °C).

Mesosphere

Thermosphere

The upper limit is about 800 km. The temperature rises to altitudes of 200-300 km, where it reaches values of the order of 1500 K, after which it remains almost constant up to high altitudes. Under the action of solar radiation and cosmic radiation, air is ionized (“polar lights”) - the main regions of the ionosphere lie inside the thermosphere. At altitudes above 300 km, atomic oxygen predominates. The upper limit of the thermosphere is largely determined by the current activity of the Sun. During periods of low activity - for example, in 2008-2009 - there is a noticeable decrease in the size of this layer.

Thermopause

The region of the atmosphere above the thermosphere. In this region, the absorption of solar radiation is insignificant and the temperature does not actually change with height.

Exosphere (scattering sphere)

Up to a height of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases in height depends on their molecular masses, the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to the decrease in gas density, the temperature drops from 0 °C in the stratosphere to −110 °C in the mesosphere. However, the kinetic energy of individual particles at altitudes of 200–250 km corresponds to a temperature of ~150 °C. Above 200 km, significant fluctuations in temperature and gas density are observed in time and space.

At an altitude of about 2000-3500 km, the exosphere gradually passes into the so-called near space vacuum, which is filled with rare particles of interplanetary gas, mainly hydrogen atoms. But this gas is only part of the interplanetary matter. The other part is composed of dust-like particles of cometary and meteoric origin. In addition to extremely rarefied dust-like particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.

Overview

Based electrical properties emitted in the atmosphere the neutrosphere and ionosphere .

Depending on the composition of the gas in the atmosphere, they emit homosphere and heterosphere. heterosphere- this is an area where gravity affects the separation of gases, since their mixing at such a height is negligible. Hence follows the variable composition of the heterosphere. Below it lies a well-mixed, homogeneous part of the atmosphere, called the homosphere. The boundary between these layers is called turbopause, it lies at an altitude of about 120 km.

Other properties of the atmosphere and effects on the human body

Already at an altitude of 5 km above sea level, an untrained person develops oxygen starvation, and without adaptation, a person's performance is significantly reduced. This is where the physiological zone of the atmosphere ends. Human breathing becomes impossible at an altitude of 9 km, although up to about 115 km the atmosphere contains oxygen.

The atmosphere provides us with the oxygen we need to breathe. However, due to the drop in the total pressure of the atmosphere as you rise to a height, the partial pressure of oxygen also decreases accordingly.

History of the formation of the atmosphere

According to the most common theory, the Earth's atmosphere has been in three different compositions throughout its history. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This so-called primary atmosphere. At the next stage, active volcanic activity led to the saturation of the atmosphere with gases other than hydrogen (carbon dioxide, ammonia, water vapor). This is how secondary atmosphere. This atmosphere was restorative. Further, the process of formation of the atmosphere was determined by the following factors:

leakage of light gases (hydrogen and helium) into interplanetary space;
chemical reactions occurring in the atmosphere under the influence of ultraviolet radiation, lightning discharges and some other factors.

Gradually, these factors led to the formation tertiary atmosphere, characterized by a much lower content of hydrogen and a much higher content of nitrogen and carbon dioxide (formed as a result of chemical reactions from ammonia and hydrocarbons).

Nitrogen

The formation of a large amount of nitrogen N 2 is due to the oxidation of the ammonia-hydrogen atmosphere by molecular oxygen O 2, which began to come from the surface of the planet as a result of photosynthesis, starting from 3 billion years ago. Nitrogen N 2 is also released into the atmosphere as a result of the denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO in the upper atmosphere.

Nitrogen N 2 enters into reactions only under specific conditions (for example, during a lightning discharge). Oxidation of molecular nitrogen by ozone during electrical discharges is used in small quantities in the industrial production of nitrogen fertilizers. It can be oxidized with low energy consumption and converted into a biologically active form by cyanobacteria (blue-green algae) and nodule bacteria that form a rhizobial symbiosis with legumes, which can be effective green manure plants that do not deplete, but enrich the soil with natural fertilizers.

Oxygen

The composition of the atmosphere began to change radically with the advent of living organisms on Earth, as a result of photosynthesis, accompanied by the release of oxygen and the absorption of carbon dioxide. Initially, oxygen was spent on the oxidation of reduced compounds - ammonia, hydrocarbons, the ferrous form of iron contained in the oceans and others. At the end of this stage, the oxygen content in the atmosphere began to grow. Gradually, a modern atmosphere with oxidizing properties formed. Since this caused serious and abrupt changes in many processes occurring in the atmosphere, lithosphere and biosphere, this event was called the Oxygen Catastrophe.

noble gases

Air pollution

Recently, man has begun to influence the evolution of the atmosphere. The result of human activity has been a constant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological epochs. Huge amounts of CO 2 are consumed during photosynthesis and absorbed by the world's oceans. This gas enters the atmosphere due to the decomposition of carbonate rocks and organic substances of plant and animal origin, as well as due to volcanism and human production activities. Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the main part (360 billion tons) coming from fuel combustion. If the growth rate of fuel combustion continues, then in the next 200-300 years the amount of CO 2 in the atmosphere will double and may lead to global climate changes.

Fuel combustion is the main source of polluting gases (СО,, SO 2). Sulfur dioxide is oxidized by atmospheric oxygen to SO 3, and nitric oxide to NO 2 in the upper atmosphere, which in turn interact with water vapor, and the resulting sulfuric acid H 2 SO 4 and nitric acid HNO 3 fall on the Earth's surface in the form so-called acid rain. Usage

Its upper limit is at an altitude of 8-10 km in polar, 10-12 km in temperate and 16-18 km in tropical latitudes; lower in winter than in summer. The lower, main layer of the atmosphere. It contains more than 80% of the total mass of atmospheric air and about 90% of all water vapor present in the atmosphere. Turbulence and convection are strongly developed in the troposphere, clouds appear, cyclones and anticyclones develop. Temperature decreases with altitude with an average vertical gradient of 0.65°/100 m

For "normal conditions" at the Earth's surface are taken: density 1.2 kg/m3, barometric pressure 101.35 kPa, temperature plus 20 °C and relative humidity 50%. These conditional indicators have a purely engineering value.

Stratosphere

The layer of the atmosphere located at an altitude of 11 to 50 km. A slight change in temperature in the 11-25 km layer (lower layer of the stratosphere) and its increase in the 25-40 km layer from −56.5 to 0.8 ° (upper stratosphere or inversion region) are typical. Having reached a value of about 273 K (almost 0 ° C) at an altitude of about 40 km, the temperature remains constant up to an altitude of about 55 km. This region of constant temperature is called the stratopause and is the boundary between the stratosphere and the mesosphere.

Stratopause

The boundary layer of the atmosphere between the stratosphere and the mesosphere. There is a maximum in the vertical temperature distribution (about 0 °C).

Mesosphere

Mesopause

Transitional layer between mesosphere and thermosphere. There is a minimum in the vertical temperature distribution (about -90°C).

Karman Line

Altitude above sea level, which is conventionally accepted as the boundary between the Earth's atmosphere and space.

Thermosphere

Exosphere (scattering sphere)

Up to a height of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases in height depends on their molecular masses, the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to the decrease in gas density, the temperature drops from 0 °C in the stratosphere to -110 °C in the mesosphere. However, the kinetic energy of individual particles at altitudes of 200–250 km corresponds to a temperature of ~1500°C. Above 200 km, significant fluctuations in temperature and gas density are observed in time and space.

At an altitude of about 2000-3000 km, the exosphere gradually passes into the so-called near space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas is only part of the interplanetary matter. The other part is composed of dust-like particles of cometary and meteoric origin. In addition to extremely rarefied dust-like particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.

The troposphere accounts for about 80% of the mass of the atmosphere, the stratosphere accounts for about 20%; the mass of the mesosphere is no more than 0.3%, the thermosphere is less than 0.05% of the total mass of the atmosphere. Based on the electrical properties in the atmosphere, the neutrosphere and ionosphere are distinguished. It is currently believed that the atmosphere extends to an altitude of 2000-3000 km.

Physical Properties

The thickness of the atmosphere is approximately 2000 - 3000 km from the Earth's surface. The total mass of air - (5.1-5.3)? 10 18 kg. The molar mass of clean dry air is 28.966. Pressure at 0 °C at sea level 101.325 kPa; critical temperature ?140.7 °C; critical pressure 3.7 MPa; C p 1.0048?10? J / (kg K) (at 0 °C), C v 0.7159 10? J/(kg K) (at 0 °C). Solubility of air in water at 0°С - 0.036%, at 25°С - 0.22%.

Physiological and other properties of the atmosphere

Already at an altitude of 5 km above sea level, an untrained person develops oxygen starvation and, without adaptation, a person's performance is significantly reduced. This is where the physiological zone of the atmosphere ends. Human breathing becomes impossible at an altitude of 15 km, although up to about 115 km the atmosphere contains oxygen.

The human lungs constantly contain about 3 liters of alveolar air. The partial pressure of oxygen in the alveolar air at normal atmospheric pressure is 110 mm Hg. Art., pressure of carbon dioxide - 40 mm Hg. Art., and water vapor - 47 mm Hg. Art. With increasing altitude, the oxygen pressure drops, and the total pressure of water vapor and carbon dioxide in the lungs remains almost constant - about 87 mm Hg. Art. The flow of oxygen into the lungs will completely stop when the pressure of the surrounding air becomes equal to this value.

At an altitude of about 19-20 km, the atmospheric pressure drops to 47 mm Hg. Art. Therefore, at this height, water and interstitial fluid begin to boil in the human body. Outside the pressurized cabin at these altitudes, death occurs almost instantly. Thus, from the point of view of human physiology, "space" begins already at an altitude of 15-19 km.

Dense layers of air - the troposphere and stratosphere - protect us from the damaging effects of radiation. With sufficient rarefaction of air, at altitudes of more than 36 km, ionizing radiation, primary cosmic rays, has an intense effect on the body; at altitudes of more than 40 km, the ultraviolet part of the solar spectrum, which is dangerous for humans, operates.

As we rise to an ever greater height above the Earth's surface, such phenomena that are familiar to us observed in the lower layers of the atmosphere, such as the propagation of sound, the emergence of aerodynamic lift and drag, heat transfer by convection, etc., gradually weaken, and then completely disappear.

In rarefied layers of air, the propagation of sound is impossible. Up to altitudes of 60-90 km, it is still possible to use air resistance and lift for controlled aerodynamic flight. But starting from altitudes of 100-130 km, the concepts of the M number and the sound barrier familiar to every pilot lose their meaning, there passes the conditional Karman Line, beyond which the sphere of purely ballistic flight begins, which can only be controlled using reactive forces.

At altitudes above 100 km, the atmosphere is also deprived of another remarkable property - the ability to absorb, conduct and transfer thermal energy by convection (i.e., by means of air mixing). This means that various elements of equipment, equipment of the orbital space station they will not be able to be cooled from the outside in the way it is usually done on an airplane - with the help of air jets and air radiators. At such a height, as in space in general, the only way to transfer heat is thermal radiation.

Composition of the atmosphere

Earth's atmosphere consists mainly of gases and various impurities (dust, water drops, ice crystals, sea salts, combustion products).

The concentration of gases that make up the atmosphere is almost constant, with the exception of water (H 2 O) and carbon dioxide (CO 2).

Composition of dry air

Gas	Content by volume, %	Content by weight, %
Nitrogen	78,084	75,50
Oxygen	20,946	23,10
Argon	0,932	1,286
Water	0,5-4	-
Carbon dioxide	0,032	0,046
Neon	1.818×10 −3	1.3×10 −3
Helium	4.6×10 −4	7.2×10 −5
Methane	1.7×10 −4	-
Krypton	1.14×10 −4	2.9×10 −4
Hydrogen	5×10 −5	7.6×10 −5
Xenon	8.7×10 −6	-
Nitrous oxide	5×10 −5	7.7×10 −5

In addition to the gases indicated in the table, the atmosphere contains SO 2, NH 3, CO, ozone, hydrocarbons, HCl, vapors, I 2, as well as many other gases in small quantities. In the troposphere there is constantly a large amount of suspended solid and liquid particles (aerosol).

History of the formation of the atmosphere

According to the most common theory, the Earth's atmosphere has been in four different compositions over time. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This so-called primary atmosphere(about four billion years ago). At the next stage, active volcanic activity led to the saturation of the atmosphere with gases other than hydrogen (carbon dioxide, ammonia, water vapor). This is how secondary atmosphere(about three billion years before our days). This atmosphere was restorative. Further, the process of formation of the atmosphere was determined by the following factors:

leakage of light gases (hydrogen and helium) into interplanetary space;
chemical reactions occurring in the atmosphere under the influence of ultraviolet radiation, lightning discharges and some other factors.

Nitrogen

The formation of a large amount of N 2 is due to the oxidation of the ammonia-hydrogen atmosphere by molecular O 2, which began to come from the surface of the planet as a result of photosynthesis, starting from 3 billion years ago. N 2 is also released into the atmosphere as a result of the denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO in the upper atmosphere.

Nitrogen N 2 enters into reactions only under specific conditions (for example, during a lightning discharge). Oxidation of molecular nitrogen by ozone during electrical discharges is used in the industrial production of nitrogen fertilizers. It can be oxidized with low energy consumption and converted into a biologically active form by cyanobacteria (blue-green algae) and nodule bacteria that form rhizobial symbiosis with legumes, the so-called. green manure.

Oxygen

The composition of the atmosphere began to change radically with the advent of living organisms on Earth, as a result of photosynthesis, accompanied by the release of oxygen and the absorption of carbon dioxide. Initially, oxygen was spent on the oxidation of reduced compounds - ammonia, hydrocarbons, the ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to grow. Gradually, a modern atmosphere with oxidizing properties formed. Since this caused serious and abrupt changes in many processes occurring in the atmosphere, lithosphere and biosphere, this event was called the Oxygen Catastrophe.

Carbon dioxide

The content of CO 2 in the atmosphere depends on volcanic activity and chemical processes in earthly shells, but most of all - on the intensity of biosynthesis and decomposition of organic matter in the Earth's biosphere. Almost the entire current biomass of the planet (about 2.4 × 10 12 tons) is formed due to carbon dioxide, nitrogen and water vapor contained in the atmospheric air. Buried in the ocean , swamps and forests , organic matter turns into coal , oil and natural gas . (see Geochemical carbon cycle)

noble gases

Air pollution

Recently, man has begun to influence the evolution of the atmosphere. The result of his activities was a constant significant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological epochs. Huge amounts of CO 2 are consumed during photosynthesis and absorbed by the world's oceans. This gas enters the atmosphere due to the decomposition of carbonate rocks and organic substances of plant and animal origin, as well as due to volcanism and human production activities. Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the main part (360 billion tons) coming from fuel combustion. If the growth rate of fuel combustion continues, then in the next 50 - 60 years the amount of CO 2 in the atmosphere will double and may lead to global climate change.

Fuel combustion is the main source of polluting gases (СО,, SO 2). Sulfur dioxide is oxidized by atmospheric oxygen to SO 3 in the upper atmosphere, which in turn interacts with water vapor and ammonia, and the resulting sulfuric acid (H 2 SO 4) and ammonium sulfate ((NH 4) 2 SO 4) return to the surface of the Earth in the form of a so-called. acid rain. The use of internal combustion engines leads to significant air pollution with nitrogen oxides, hydrocarbons and lead compounds (tetraethyl lead Pb (CH 3 CH 2) 4)).

Aerosol pollution of the atmosphere is due to both natural causes (volcanic eruptions, dust storms, sea water and plant pollen, etc.), and human economic activity (mining of ores and building materials, fuel combustion, cement production, etc.). Intense large-scale removal of solid particles into the atmosphere is one of the possible causes of climate change on the planet.

Literature

V. V. Parin, F. P. Kosmolinsky, B. A. Dushkov "Space biology and medicine" (2nd edition, revised and enlarged), M.: "Prosveshchenie", 1975, 223 pages.
N. V. Gusakova "Chemistry environment", Rostov-on-Don: Phoenix, 2004, 192 with ISBN 5-222-05386-5
Sokolov V. A. Geochemistry of natural gases, M., 1971;
McEwen M., Phillips L.. Atmospheric Chemistry, M., 1978;
Wark K., Warner S., Air pollution. Sources and control, trans. from English, M.. 1980;
Background pollution monitoring natural environments. v. 1, L., 1982.

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Earth's atmosphere

The atmosphere began to form along with the formation of the Earth. In the course of the evolution of the planet and as its parameters approached modern values, there were fundamentally qualitative changes in its chemical composition and physical properties. According to the evolutionary model, at an early stage, the Earth was in a molten state and formed as a solid body about 4.5 billion years ago. This milestone is taken as the beginning of the geological chronology. Since that time, the slow evolution of the atmosphere began. Some geological processes (for example, outpouring of lava during volcanic eruptions) were accompanied by the release of gases from the bowels of the Earth. They included nitrogen, ammonia, methane, water vapor, CO2 oxide and CO2 carbon dioxide. Under the influence of solar ultraviolet radiation, water vapor decomposed into hydrogen and oxygen, but the released oxygen reacted with carbon monoxide, forming carbon dioxide. Ammonia decomposed into nitrogen and hydrogen. Hydrogen, in the process of diffusion, rose up and left the atmosphere, while heavier nitrogen could not escape and gradually accumulated, becoming the main component, although some of it was bound into molecules as a result of chemical reactions ( cm. CHEMISTRY OF THE ATMOSPHERE). Under the influence of ultraviolet rays and electrical discharges, a mixture of gases present in the original atmosphere of the Earth entered into chemical reactions, as a result of which organic substances, in particular amino acids, were formed. With the advent of primitive plants, the process of photosynthesis began, accompanied by the release of oxygen. This gas, especially after diffusion into the upper atmosphere, began to protect its lower layers and the Earth's surface from life-threatening ultraviolet and X-ray radiation. According to theoretical estimates, the oxygen content, which is 25,000 times less than now, could already lead to the formation of an ozone layer with only half as much as it is now. However, this is already enough to provide a very significant protection of organisms from the damaging effects of ultraviolet rays.

It is likely that the primary atmosphere contained a lot of carbon dioxide. It was consumed during photosynthesis, and its concentration must have decreased as the plant world evolved, and also due to absorption during some geological processes. Insofar as the greenhouse effect associated with the presence of carbon dioxide in the atmosphere, fluctuations in its concentration are one of the important causes of such large-scale climatic changes in the history of the Earth, such as ice ages.

Helium present in the modern atmosphere for the most part is a product radioactive decay uranium, thorium and radium. These radioactive elements emit a-particles, which are the nuclei of helium atoms. Since no electric charge is formed and does not disappear during radioactive decay, with the formation of each a-particle, two electrons appear, which, recombining with a-particles, form neutral helium atoms. Radioactive elements are contained in minerals dispersed in the thickness of rocks, so a significant part of the helium formed as a result of radioactive decay is stored in them, volatilizing very slowly into the atmosphere. A certain amount of helium rises up into the exosphere due to diffusion, but due to the constant influx from the earth's surface, the volume of this gas in the atmosphere remains almost unchanged. Based spectral analysis light from stars and the study of meteorites, one can estimate the relative abundance of various chemical elements in the Universe. The concentration of neon in space is about ten billion times higher than on Earth, krypton - ten million times, and xenon - a million times. It follows from this that the concentration of these inert gases, apparently originally present in the Earth's atmosphere and not replenished in the course of chemical reactions, greatly decreased, probably even at the stage of the Earth's loss of its primary atmosphere. An exception is the inert gas argon, since it is still formed in the form of the 40 Ar isotope in the process of radioactive decay of the potassium isotope.

Barometric pressure distribution.

The total weight of atmospheric gases is approximately 4.5 10 15 tons. Thus, the "weight" of the atmosphere per unit area, or atmospheric pressure, is approximately 11 t / m 2 = 1.1 kg / cm 2 at sea level. Pressure equal to P 0 \u003d 1033.23 g / cm 2 \u003d 1013.250 mbar \u003d 760 mm Hg. Art. = 1 atm, taken as the standard mean atmospheric pressure. For an atmosphere in hydrostatic equilibrium, we have: d P= -rgd h, which means that on the interval of heights from h before h+d h takes place equality between atmospheric pressure change d P and the weight of the corresponding element of the atmosphere with unit area, density r and thickness d h. As a ratio between pressure R and temperature T used sufficiently applicable for earth's atmosphere equation of state ideal gas with density r: P= r R T/m, where m is the molecular weight, and R = 8.3 J/(K mol) is the universal gas constant. Then dlog P= – (m g/RT)d h= -bd h= – d h/H, where the pressure gradient is on a logarithmic scale. The reciprocal of H is to be called the scale of the height of the atmosphere.

When integrating this equation for an isothermal atmosphere ( T= const) or for its part, where such an approximation is acceptable, the barometric law of pressure distribution with altitude is obtained: P = P 0 exp(- h/H 0), where the height reading h produced from ocean level, where the standard mean pressure is P 0 . Expression H 0=R T/ mg, is called the height scale, which characterizes the extent of the atmosphere, provided that the temperature in it is the same everywhere (isothermal atmosphere). If the atmosphere is not isothermal, then it is necessary to integrate taking into account the change in temperature with height, and the parameter H- some local characteristic of the layers of the atmosphere, depending on their temperature and the properties of the medium.

Standard atmosphere.

Model (table of values of the main parameters) corresponding to the standard pressure at the base of the atmosphere R 0 and chemical composition is called the standard atmosphere. More precisely, this is a conditional model of the atmosphere, for which the average values of temperature, pressure, density, viscosity, and other air characteristics for a latitude of 45° 32° 33І are set at altitudes from 2 km below sea level to the outer boundary of the earth's atmosphere. The parameters of the middle atmosphere at all altitudes were calculated using the ideal gas equation of state and the barometric law assuming that at sea level the pressure is 1013.25 hPa (760 mmHg) and the temperature is 288.15 K (15.0°C). According to the nature of the vertical temperature distribution, the average atmosphere consists of several layers, in each of which the temperature is approximated by a linear function of height. In the lowest of the layers - the troposphere (h Ј 11 km), the temperature drops by 6.5 ° C with each kilometer of ascent. At high altitudes, the value and sign of the vertical temperature gradient change from layer to layer. Above 790 km, the temperature is about 1000 K and practically does not change with altitude.

The standard atmosphere is a periodically updated, legalized standard, issued in the form of tables.

Table 1. Standard Earth Atmosphere Model

Table 1. STANDARD EARTH ATMOSPHERE MODEL. The table shows: h- height from sea level, R- pressure, T– temperature, r – density, N is the number of molecules or atoms per unit volume, H- height scale, l is the length of the free path. Pressure and temperature at an altitude of 80–250 km, obtained from rocket data, have lower values. Extrapolated values for altitudes greater than 250 km are not very accurate.
h(km)	P(mbar)	T(°C)	r (g / cm 3)	N(cm -3)	H(km)	l(cm)
0	1013	288	1.22 10 -3	2.55 10 19	8,4	7.4 10 -6
1	899	281	1.11 10 -3	2.31 10 19		8.1 10 -6
2	795	275	1.01 10 -3	2.10 10 19		8.9 10 -6
3	701	268	9.1 10 -4	1.89 10 19		9.9 10 -6
4	616	262	8.2 10 -4	1.70 10 19		1.1 10 -5
5	540	255	7.4 10 -4	1.53 10 19	7,7	1.2 10 -5
6	472	249	6.6 10 -4	1.37 10 19		1.4 10 -5
8	356	236	5.2 10 -4	1.09 10 19		1.7 10 -5
10	264	223	4.1 10 -4	8.6 10 18	6,6	2.2 10 -5
15	121	214	1.93 10 -4	4.0 10 18		4.6 10 -5
20	56	214	8.9 10 -5	1.85 10 18	6,3	1.0 10 -4
30	12	225	1.9 10 -5	3.9 10 17	6,7	4.8 10 -4
40	2,9	268	3.9 10 -6	7.6 10 16	7,9	2.4 10 -3
50	0,97	276	1.15 10 -6	2.4 10 16	8,1	8.5 10 -3
60	0,28	260	3.9 10 -7	7.7 10 15	7,6	0,025
70	0,08	219	1.1 10 -7	2.5 10 15	6,5	0,09
80	0,014	205	2.7 10 -8	5.0 10 14	6,1	0,41
90	2.8 10 -3	210	5.0 10 -9	9 10 13	6,5	2,1
100	5.8 10 -4	230	8.8 10 -10	1.8 10 13	7,4	9
110	1.7 10 -4	260	2.1 10 –10	5.4 10 12	8,5	40
120	6 10 -5	300	5.6 10 -11	1.8 10 12	10,0	130
150	5 10 -6	450	3.2 10 -12	9 10 10	15	1.8 10 3
200	5 10 -7	700	1.6 10 -13	5 10 9	25	3 10 4
250	9 10 -8	800	3 10 -14	8 10 8	40	3 10 5
300	4 10 -8	900	8 10 -15	3 10 8	50
400	8 10 -9	1000	1 10 –15	5 10 7	60
500	2 10 -9	1000	2 10 -16	1 10 7	70
700	2 10 –10	1000	2 10 -17	1 10 6	80
1000	1 10 –11	1000	1 10 -18	1 10 5	80

Troposphere.

The lowest and densest layer of the atmosphere, in which the temperature decreases rapidly with height, is called the troposphere. It contains up to 80% of the total mass of the atmosphere and extends in polar and middle latitudes up to heights of 8–10 km, and in the tropics up to 16–18 km. Almost all weather-forming processes develop here, heat and moisture exchange occurs between the Earth and its atmosphere, clouds form, various meteorological phenomena occur, fogs and precipitation occur. These layers of the earth's atmosphere are in convective equilibrium and, due to active mixing, have a homogeneous chemical composition, mainly from molecular nitrogen (78%) and oxygen (21%). The vast majority of natural and man-made aerosol and gas air pollutants are concentrated in the troposphere. The dynamics of the lower part of the troposphere up to 2 km thick strongly depends on the properties of the underlying surface of the Earth, which determines the horizontal and vertical movements of air (winds) due to the transfer of heat from a warmer land through the IR radiation of the earth's surface, which is absorbed in the troposphere, mainly by vapor water and carbon dioxide (greenhouse effect). The temperature distribution with height is established as a result of turbulent and convective mixing. On average, it corresponds to a drop in temperature with height of about 6.5 K/km.

The wind speed in the surface boundary layer first increases rapidly with height, and higher it continues to increase by 2–3 km/s per kilometer. Sometimes in the troposphere there are narrow planetary streams (with a speed of more than 30 km / s), western ones in middle latitudes, and eastern ones near the equator. They are called jet streams.

tropopause.

At the upper boundary of the troposphere (tropopause), the temperature reaches its minimum value for the lower atmosphere. This is the transition layer between the troposphere and the stratosphere above it. The thickness of the tropopause is from hundreds of meters to 1.5–2 km, and the temperature and altitude, respectively, range from 190 to 220 K and from 8 to 18 km, depending on the geographic latitude and season. In temperate and high latitudes, in winter it is 1–2 km lower than in summer and 8–15 K warmer. In the tropics, seasonal changes are much less (altitude 16–18 km, temperature 180–200 K). Above jet streams possible rupture of the tropopause.

Water in the Earth's atmosphere.

The most important feature of the Earth's atmosphere is the presence of a significant amount of water vapor and water in droplet form, which is most easily observed in the form of clouds and cloud structures. The degree of cloud coverage of the sky (at a certain moment or on average over a certain period of time), expressed on a 10-point scale or as a percentage, is called cloudiness. The shape of the clouds is determined by the international classification. On average, clouds cover about half of the globe. Cloudiness is an important factor characterizing weather and climate. In winter and at night, cloudiness prevents a decrease in the temperature of the earth's surface and the surface layer of air, in summer and during the day it weakens the heating of the earth's surface by the sun's rays, softening the climate inside the continents.

Clouds.

Clouds are accumulations of water droplets suspended in the atmosphere (water clouds), ice crystals (ice clouds), or both (mixed clouds). As drops and crystals become larger, they fall out of the clouds in the form of precipitation. Clouds form mainly in the troposphere. They result from the condensation of water vapor contained in the air. The diameter of cloud drops is on the order of several microns. The content of liquid water in clouds is from fractions to several grams per m3. Clouds are distinguished by height: According to the international classification, there are 10 genera of clouds: cirrus, cirrocumulus, cirrostratus, altocumulus, altostratus, stratonimbus, stratus, stratocumulus, cumulonimbus, cumulus.

Mother-of-pearl clouds are also observed in the stratosphere, and noctilucent clouds in the mesosphere.

Cirrus clouds - transparent clouds in the form of thin white threads or veils with a silky sheen, not giving a shadow. Cirrus clouds are made up of ice crystals and form in the upper troposphere at very low temperatures. Some types of cirrus clouds serve as harbingers of weather changes.

Cirrocumulus clouds are ridges or layers of thin white clouds in the upper troposphere. Cirrocumulus clouds are built from small elements that look like flakes, ripples, small balls without shadows and consist mainly of ice crystals.

Cirrostratus clouds - a whitish translucent veil in the upper troposphere, usually fibrous, sometimes blurry, consisting of small needle or columnar ice crystals.

Altocumulus clouds are white, gray or white-gray clouds of the lower and middle layers of the troposphere. Altocumulus clouds look like layers and ridges, as if built from plates lying one above the other, rounded masses, shafts, flakes. Altocumulus clouds form during intense convective activity and usually consist of supercooled water droplets.

Altostratus clouds are grayish or bluish clouds of a fibrous or uniform structure. Altostratus clouds are observed in the middle troposphere, extending several kilometers in height and sometimes thousands of kilometers in a horizontal direction. Usually, altostratus clouds are part of frontal cloud systems associated with ascending movements of air masses.

Nimbostratus clouds - a low (from 2 km and above) amorphous layer of clouds of a uniform gray color, giving rise to overcast rain or snow. Nimbostratus clouds - highly developed vertically (up to several km) and horizontally (several thousand km), consist of supercooled water drops mixed with snowflakes, usually associated with atmospheric fronts.

Stratus clouds - clouds of the lower tier in the form of a homogeneous layer without definite outlines, gray in color. The height of stratus clouds above the earth's surface is 0.5–2 km. Occasional drizzle falls from stratus clouds.

Cumulus clouds are dense, bright white clouds during the day with significant vertical development (up to 5 km or more). The upper parts of cumulus clouds look like domes or towers with rounded outlines. Cumulus clouds usually form as convection clouds in cold air masses.

Stratocumulus clouds - low (below 2 km) clouds in the form of gray or white non-fibrous layers or ridges of round large blocks. The vertical thickness of stratocumulus clouds is small. Occasionally, stratocumulus clouds give light precipitation.

Cumulonimbus clouds are powerful and dense clouds with a strong vertical development (up to a height of 14 km), giving heavy rainfall with thunderstorms, hail, squalls. Cumulonimbus clouds develop from powerful cumulus clouds, differing from them top made up of ice crystals.

Stratosphere.

Through the tropopause, on average at altitudes from 12 to 50 km, the troposphere passes into the stratosphere. In the lower part, for about 10 km, i.e. up to heights of about 20 km, it is isothermal (temperature about 220 K). Then it increases with altitude, reaching a maximum of about 270 K at an altitude of 50–55 km. Here is the boundary between the stratosphere and the overlying mesosphere, called the stratopause. .

There is much less water vapor in the stratosphere. Nevertheless, thin translucent mother-of-pearl clouds are occasionally observed, occasionally appearing in the stratosphere at a height of 20–30 km. Mother-of-pearl clouds are visible in the dark sky after sunset and before sunrise. In shape, mother-of-pearl clouds resemble cirrus and cirrocumulus clouds.

Middle atmosphere (mesosphere).

At an altitude of about 50 km, the mesosphere begins with the peak of a wide temperature maximum. . The reason for the increase in temperature in the region of this maximum is an exothermic (i.e., accompanied by the release of heat) photochemical reaction of ozone decomposition: O 3 + hv® O 2 + O. Ozone arises as a result of the photochemical decomposition of molecular oxygen O 2

About 2+ hv® O + O and the subsequent reaction of a triple collision of an atom and an oxygen molecule with some third molecule M.

O + O 2 + M ® O 3 + M

Ozone greedily absorbs ultraviolet radiation in the region from 2000 to 3000Å, and this radiation heats up the atmosphere. Ozone, located in the upper atmosphere, serves as a kind of shield that protects us from the action of ultraviolet radiation from the sun. Without this shield, the development of life on Earth in its modern forms would hardly have been possible.

In general, throughout the mesosphere, the temperature of the atmosphere decreases to its minimum value of about 180 K at the upper boundary of the mesosphere (called the mesopause, height is about 80 km). In the vicinity of the mesopause, at altitudes of 70–90 km, a very thin layer of ice crystals and particles of volcanic and meteorite dust can appear, observed in the form of a beautiful spectacle of noctilucent clouds. shortly after sunset.

In the mesosphere, for the most part, small solid meteorite particles that fall on the Earth are burned, causing the phenomenon of meteors.

Meteors, meteorites and fireballs.

Flares and other phenomena in the upper atmosphere of the Earth caused by the intrusion into it at a speed of 11 km / s and above solid cosmic particles or bodies are called meteoroids. There is an observed bright meteor trail; the most powerful phenomena, often accompanied by the fall of meteorites, are called fireballs; meteors are associated with meteor showers.

meteor shower:

1) the phenomenon of multiple meteor falls over several hours or days from one radiant.

2) a swarm of meteoroids moving in one orbit around the Sun.

The systematic appearance of meteors in a certain region of the sky and on certain days of the year, caused by the intersection of the Earth's orbit with a common orbit of many meteorite bodies moving at approximately the same and equally directed speeds, due to which their paths in the sky seem to come out of one common point (radiant) . They are named after the constellation where the radiant is located.

Meteor showers make a deep impression with their lighting effects, but individual meteors are rarely seen. Far more numerous are invisible meteors, too small to be seen at the moment they are swallowed up by the atmosphere. Some of the smallest meteors probably do not heat up at all, but are only captured by the atmosphere. These small particles with sizes from a few millimeters to ten-thousandths of a millimeter are called micrometeorites. The amount of meteoric matter entering the atmosphere every day is from 100 to 10,000 tons, with most of this matter being micrometeorites.

Since meteoric matter partially burns up in the atmosphere, its gas composition is replenished with traces of various chemical elements. For example, stone meteors bring lithium into the atmosphere. The combustion of metallic meteors leads to the formation of tiny spherical iron, iron-nickel and other droplets that pass through the atmosphere and are deposited on the earth's surface. They can be found in Greenland and Antarctica, where ice sheets remain almost unchanged for years. Oceanologists find them in bottom ocean sediments.

Most of the meteor particles entering the atmosphere are deposited within approximately 30 days. Some scientists believe that this cosmic dust plays an important role in the formation of atmospheric phenomena such as rain, as it serves as the nuclei of water vapor condensation. Therefore, it is assumed that precipitation is statistically associated with large meteor showers. However, some experts believe that since the total input of meteoric matter is many tens of times greater than even with the largest meteor shower, the change in the total amount of this material that occurs as a result of one such shower can be neglected.

However, there is no doubt that the largest micrometeorites and visible meteorites leave long traces of ionization in the high layers of the atmosphere, mainly in the ionosphere. Such traces can be used for long-distance radio communications, as they reflect high-frequency radio waves.

The energy of meteors entering the atmosphere is spent mainly, and perhaps completely, on its heating. This is one of the secondary heat balance atmosphere.

A meteorite is a solid body of natural origin that fell to the surface of the Earth from space. Usually distinguish stone, iron-stone and iron meteorites. The latter are mainly composed of iron and nickel. Among the found meteorites, most have a weight of several grams to several kilograms. The largest of those found, the Goba iron meteorite weighs about 60 tons and still lies in the same place where it was discovered, in South Africa. Most meteorites are fragments of asteroids, but some meteorites may have come to Earth from the Moon and even from Mars.

A fireball is a very bright meteor, sometimes observed even during the day, often leaving behind a smoky trail and accompanied by sound phenomena; often ends with the fall of meteorites.

Thermosphere.

Above the temperature minimum of the mesopause, the thermosphere begins, in which the temperature, at first slowly, and then quickly, begins to rise again. The reason is the absorption of ultraviolet, solar radiation at altitudes of 150–300 km, due to the ionization of atomic oxygen: O + hv® O + + e.

In the thermosphere, the temperature continuously rises to a height of about 400 km, where it reaches 1800 K in the daytime during the epoch of maximum solar activity. In the epoch of minimum, this limiting temperature can be less than 1000 K. Above 400 km, the atmosphere passes into an isothermal exosphere. The critical level (the base of the exosphere) is located at an altitude of about 500 km.

Auroras and many orbits of artificial satellites, as well as noctilucent clouds - all these phenomena occur in the mesosphere and thermosphere.

Polar Lights.

At high latitudes, auroras are observed during magnetic field disturbances. They may last for several minutes, but are often visible for several hours. Auroras vary greatly in shape, color and intensity, all of which sometimes change very rapidly over time. The aurora spectrum consists of emission lines and bands. Some of the emissions from the night sky are enhanced in the aurora spectrum, primarily the green and red lines of l 5577 Å and l 6300 Å of oxygen. It happens that one of these lines is many times more intense than the other, and this determines the visible color of the radiance: green or red. Disturbances in the magnetic field are also accompanied by disruptions in radio communications in the polar regions. The disruption is caused by changes in the ionosphere, which means that during magnetic storms a powerful source of ionization operates. It has been established that strong magnetic storms occur when there are large groups of spots near the center of the solar disk. Observations have shown that storms are associated not with the spots themselves, but with solar flares that appear during the development of a group of spots.

The auroras are a range of light of varying intensity with rapid movements observed in the high latitude regions of the Earth. The visual aurora contains green (5577Å) and red (6300/6364Å) emission lines of atomic oxygen and N 2 molecular bands, which are excited by energetic particles of solar and magnetospheric origin. These emissions are usually displayed at an altitude of about 100 km and above. The term optical aurora is used to refer to the visual auroras and their infrared to ultraviolet emission spectrum. The radiation energy in the infrared part of the spectrum significantly exceeds the energy of the visible region. When auroras appeared, emissions were observed in the ULF range (

The actual forms of auroras are difficult to classify; The following terms are most commonly used:

1. Calm uniform arcs or stripes. The arc usually extends for ~1000 km in the direction of the geomagnetic parallel (toward the Sun in the polar regions) and has a width from one to several tens of kilometers. A strip is a generalization of the concept of an arc, it usually does not have a regular arcuate shape, but bends in the form of an S or in the form of spirals. Arcs and bands are located at altitudes of 100–150 km.

2. Rays of aurora . This term refers to an auroral structure extended along magnetic lines of force, with a vertical length from several tens to several hundreds of kilometers. The length of the rays along the horizontal is small, from several tens of meters to several kilometers. Rays are usually observed in arcs or as separate structures.

3. Stains or surfaces . These are isolated areas of glow that do not have a specific shape. Individual spots may be related.

4. Veil. An unusual form of aurora, which is a uniform glow that covers large areas of the sky.

According to the structure, the auroras are divided into homogeneous, polish and radiant. Various terms are used; pulsating arc, pulsating surface, diffuse surface, radiant stripe, drapery, etc. There is a classification of auroras according to their color. According to this classification, auroras of the type A. The upper part or completely are red (6300–6364 Å). They usually appear at altitudes of 300–400 km during high geomagnetic activity.

Aurora type V are colored red in the lower part and are associated with the luminescence of the bands of the first positive N 2 system and the first negative O 2 system. Such forms of aurora appear during the most active phases of auroras.

Zones auroras – these are zones of maximum frequency of occurrence of auroras at night, according to observers at a fixed point on the Earth's surface. The zones are located at 67° north and south latitude, and their width is about 6°. The maximum occurrence of auroras, corresponding to a given moment of local geomagnetic time, occurs in oval-like belts (aurora oval), which are located asymmetrically around the north and south geomagnetic poles. The aurora oval is fixed in latitude-time coordinates, and the aurora zone is the locus of points in the midnight region of the oval in latitude-longitude coordinates. The oval belt is located approximately 23° from the geomagnetic pole in the night sector and 15° in the day sector.

Auroral oval and aurora zones. The location of the aurora oval depends on geomagnetic activity. The oval becomes wider at high geomagnetic activity. Aurora zones or aurora oval boundaries are better represented by L 6.4 than by dipole coordinates. The geomagnetic field lines at the boundary of the daytime sector of the aurora oval coincide with magnetopause. There is a change in the position of the aurora oval depending on the angle between the geomagnetic axis and the Earth-Sun direction. The auroral oval is also determined on the basis of data on the precipitation of particles (electrons and protons) of certain energies. Its position can be independently determined from data on caspakh on the dayside and in the magnetotail.

The daily variation in the frequency of occurrence of auroras in the aurora zone has a maximum at geomagnetic midnight and a minimum at geomagnetic noon. On the near-equatorial side of the oval, the frequency of occurrence of auroras sharply decreases, but the shape of diurnal variations is retained. On the polar side of the oval, the frequency of occurrence of auroras decreases gradually and is characterized by complex diurnal changes.

Intensity of auroras.

Aurora Intensity determined by measuring the apparent luminance surface. Brightness surface I auroras in a certain direction is determined by the total emission 4p I photon/(cm 2 s). Since this value is not the true surface brightness, but represents the emission from the column, the unit photon/(cm 2 column s) is usually used in the study of auroras. The usual unit for measuring total emission is Rayleigh (Rl) equal to 10 6 photon / (cm 2 column s). A more practical unit of aurora intensity is determined from the emissions of a single line or band. For example, the intensity of the auroras is determined by the international brightness coefficients (ICF) according to the green line intensity data (5577 Å); 1 kRl = I MKH, 10 kRl = II MKH, 100 kRl = III MKH, 1000 kRl = IV MKH (maximum aurora intensity). This classification cannot be used for red auroras. One of the discoveries of the epoch (1957–1958) was the establishment of the spatial and temporal distribution of auroras in the form of an oval displaced relative to the magnetic pole. From simple ideas about the circular shape of the distribution of auroras relative to the magnetic pole, the transition to modern physics of the magnetosphere was completed. The honor of the discovery belongs to O. Khorosheva, and G. Starkov, J. Feldshtein, S-I. The aurora oval is the region of the most intense impact of the solar wind on the Earth's upper atmosphere. The intensity of auroras is greatest in the oval, and its dynamics are continuously monitored by satellites.

Stable auroral red arcs.

Steady auroral red arc, otherwise called the mid-latitude red arc or M-arc, is a subvisual (below the sensitivity limit of the eye) wide arc, stretched from east to west for thousands of kilometers and encircling, possibly, the entire Earth. The latitudinal extent of the arc is 600 km. The emission from the stable auroral red arc is almost monochromatic in the red lines l 6300 Å and l 6364 Å. Recently, weak emission lines l 5577 Å (OI) and l 4278 Å (N + 2) have also been reported. Persistent red arcs are classified as auroras, but they appear at much higher altitudes. The lower limit is located at an altitude of 300 km, the upper limit is about 700 km. The intensity of the quiet auroral red arc in the l 6300 Å emission ranges from 1 to 10 kRl (a typical value is 6 kRl). The sensitivity threshold of the eye at this wavelength is about 10 kR, so arcs are rarely observed visually. However, observations have shown that their brightness is >50 kR on 10% of nights. The usual lifetime of arcs is about one day, and they rarely appear on subsequent days. Radio waves from satellites or radio sources crossing stable auroral red arcs are subject to scintillations, indicating the existence of electron density inhomogeneities. The theoretical explanation of the red arcs is that the heated electrons of the region F ionospheres cause an increase in oxygen atoms. Satellite observations show an increase in electron temperature along geomagnetic field lines that cross stable auroral red arcs. The intensity of these arcs correlates positively with geomagnetic activity (storms), and the frequency of occurrence of arcs correlates positively with solar spot-forming activity.

Changing aurora.

Some forms of auroras experience quasi-periodic and coherent temporal intensity variations. These auroras, with roughly stationary geometry and rapid periodic variations occurring in phase, are called changing auroras. They are classified as auroras forms R according to the International Atlas of the Aurora. A more detailed subdivision of the changing auroras:

R 1 (pulsating aurora) is a glow with uniform phase variations in brightness throughout the form of the aurora. By definition, in an ideal pulsating aurora, the spatial and temporal parts of the pulsation can be separated, i.e. brightness I(r,t)= I s(r)· I T(t). In a typical aurora R 1, pulsations occur with a frequency of 0.01 to 10 Hz of low intensity (1–2 kR). Most auroras R 1 are spots or arcs that pulsate with a period of several seconds.

R 2 (fiery aurora). This term is usually used to refer to movements like flames filling the sky, and not to describe a single form. The auroras are arc-shaped and usually move upward from a height of 100 km. These auroras are relatively rare and occur more often outside of the auroras.

R 3 (flickering aurora). These are auroras with rapid, irregular or regular variations in brightness, giving the impression of a flickering flame in the sky. They appear shortly before the collapse of the aurora. Commonly observed variation frequency R 3 is equal to 10 ± 3 Hz.

The term streaming aurora, used for another class of pulsating auroras, refers to irregular variations in brightness moving rapidly horizontally in arcs and bands of auroras.

The changing aurora is one of the solar-terrestrial phenomena accompanying pulsations of the geomagnetic field and auroral X-ray radiation caused by the precipitation of particles of solar and magnetospheric origin.

The glow of the polar cap is characterized by a high intensity of the band of the first negative N + 2 system (λ 3914 Å). Usually these N + 2 bands are five times more intense than the green line OI l 5577 Å, the absolute intensity of the polar cap glow is from 0.1 to 10 kRl (usually 1–3 kRl). With these auroras, which appear during PCA periods, a uniform glow covers the entire polar cap up to the geomagnetic latitude of 60° at altitudes of 30 to 80 km. It is generated mainly by solar protons and d-particles with energies of 10–100 MeV, which create an ionization maximum at these heights. There is another type of glow in the aurora zones, called mantle auroras. For this type of auroral glow, the daily intensity maximum in the morning hours is 1–10 kR, and the intensity minimum is five times weaker. Observations of mantle auroras are few and their intensity depends on geomagnetic and solar activity.

Atmospheric glow is defined as radiation produced and emitted by a planet's atmosphere. This is the non-thermal radiation of the atmosphere, with the exception of the emission of auroras, lightning discharges and the emission of meteor trails. This term is used in relation to the earth's atmosphere (night glow, twilight glow and day glow). Atmospheric glow is only a fraction of the light available in the atmosphere. Other sources are starlight, zodiacal light, and daytime scattered light from the Sun. At times, the glow of the atmosphere can be up to 40% of the total amount of light. Airglow occurs in atmospheric layers of varying height and thickness. The atmospheric glow spectrum covers wavelengths from 1000 Å to 22.5 µm. The main emission line in the airglow is l 5577 Å, which appears at a height of 90–100 km in a layer 30–40 km thick. The appearance of the glow is due to the Champen mechanism based on the recombination of oxygen atoms. Other emission lines are l 6300 Å, appearing in the case of dissociative O + 2 recombination and emission NI l 5198/5201 Å and NI l 5890/5896 Å.

The intensity of atmospheric glow is measured in Rayleighs. The brightness (in Rayleighs) is equal to 4 rb, where c is the angular surface of the luminance of the emitting layer in units of 10 6 photon/(cm 2 sr s). The glow intensity depends on latitude (differently for different emissions), and also varies during the day with a maximum near midnight. A positive correlation was noted for the airglow in the l 5577 Å emission with the number of sunspots and the flux of solar radiation at a wavelength of 10.7 cm. The airglow was observed during satellite experiments. From outer space, it looks like a ring of light around the Earth and has a greenish color.

Ozonosphere.

At altitudes of 20–25 km, the maximum concentration of a negligible amount of ozone O 3 (up to 2×10–7 of the oxygen content!), which occurs under the action of solar ultraviolet radiation at altitudes of about 10 to 50 km, is reached, protecting the planet from ionizing solar radiation. Despite the extremely small number of ozone molecules, they protect all life on Earth from the harmful effects of short-wave (ultraviolet and X-ray) radiation from the Sun. If you precipitate all the molecules to the base of the atmosphere, you get a layer no more than 3–4 mm thick! At altitudes above 100 km, the proportion of light gases increases, and at very high altitudes, helium and hydrogen predominate; many molecules dissociate into separate atoms, which, being ionized under the influence of hard solar radiation, form the ionosphere. The pressure and density of air in the Earth's atmosphere decrease with height. Depending on the distribution of temperature, the Earth's atmosphere is divided into the troposphere, stratosphere, mesosphere, thermosphere and exosphere. .

At an altitude of 20-25 km is located ozone layer. Ozone is formed due to the decay of oxygen molecules during the absorption of solar ultraviolet radiation with wavelengths shorter than 0.1–0.2 microns. Free oxygen combines with O 2 molecules and forms O 3 ozone, which greedily absorbs all ultraviolet light shorter than 0.29 microns. Ozone molecules O 3 are easily destroyed by short-wave radiation. Therefore, despite its rarefaction, the ozone layer effectively absorbs the ultraviolet radiation of the Sun, which has passed through higher and more transparent atmospheric layers. Thanks to this, living organisms on Earth are protected from the harmful effects of ultraviolet light from the Sun.

Ionosphere.

Solar radiation ionizes the atoms and molecules of the atmosphere. The degree of ionization becomes significant already at an altitude of 60 kilometers and steadily increases with distance from the Earth. At different altitudes in the atmosphere, successive processes of dissociation of various molecules and subsequent ionization of various atoms and ions occur. Basically, these are oxygen molecules O 2, nitrogen N 2 and their atoms. Depending on the intensity of these processes, various layers of the atmosphere lying above 60 kilometers are called ionospheric layers. , and their totality is the ionosphere . The lower layer, the ionization of which is insignificant, is called the neutrosphere.

The maximum concentration of charged particles in the ionosphere is reached at altitudes of 300–400 km.

History of the study of the ionosphere.

The hypothesis of the existence of a conductive layer in the upper atmosphere was put forward in 1878 by the English scientist Stuart to explain the features of the geomagnetic field. Then in 1902, independently of each other, Kennedy in the USA and Heaviside in England pointed out that in order to explain the propagation of radio waves over long distances, it is necessary to assume the existence of regions with high conductivity in the high layers of the atmosphere. In 1923, Academician M.V. Shuleikin, considering the features of the propagation of radio waves of various frequencies, came to the conclusion that there are at least two reflective layers in the ionosphere. Then, in 1925, the English researchers Appleton and Barnet, as well as Breit and Tuve, experimentally proved for the first time the existence of regions that reflect radio waves, and laid the foundation for their systematic study. Since that time, a systematic study of the properties of these layers, generally called the ionosphere, has been carried out, playing a significant role in a number of geophysical phenomena that determine the reflection and absorption of radio waves, which is very important for practical purposes, in particular, to ensure reliable radio communications.

In the 1930s, systematic observations of the state of the ionosphere began. In our country, on the initiative of M.A. Bonch-Bruevich, installations for its pulsed sounding were created. Many general properties of the ionosphere, heights and electron density of its main layers were investigated.

At altitudes of 60–70 km, the D layer is observed; at altitudes of 100–120 km, the E, at altitudes, at altitudes of 180–300 km double layer F 1 and F 2. The main parameters of these layers are given in Table 4.

Table 4

Table 4
Ionosphere region	Maximum height, km	T i , K	Day		Night ne , cm -3	a΄, ρm 3 s – 1
Ionosphere region	Maximum height, km	T i , K	min ne , cm -3	Max ne , cm -3	Night ne , cm -3	a΄, ρm 3 s – 1
D	70	20	100	200	10	10 –6
E	110	270	1.5 10 5	3 10 5	3000	10 –7
F 1	180	800–1500	3 10 5	5 10 5	–	3 10 -8
F 2 (winter)	220–280	1000–2000	6 10 5	25 10 5	~10 5	2 10 –10
F 2 (summer)	250–320	1000–2000	2 10 5	8 10 5	~3 10 5	10 –10
ne is the electron concentration, e is the electron charge, T i is the ion temperature, a΄ is the recombination coefficient (which determines the ne and its change over time)

Averages are given as they vary for different latitudes, times of day and seasons. Such data is necessary to ensure long-range radio communications. They are used in selecting operating frequencies for various shortwave radio links. Knowing their change depending on the state of the ionosphere at different times of the day and in different seasons is extremely important for ensuring the reliability of radio communications. The ionosphere is a collection of ionized layers of the earth's atmosphere, starting from altitudes of about 60 km and extending to altitudes of tens of thousands of km. The main source of ionization of the Earth's atmosphere is the ultraviolet and X-ray radiation of the Sun, which occurs mainly in the solar chromosphere and corona. In addition, the degree of ionization of the upper atmosphere is affected by solar corpuscular streams that occur during solar flares, as well as cosmic rays and meteor particles.

Ionospheric layers

are areas in the atmosphere in which the maximum values of the concentration of free electrons are reached (i.e., their number per unit volume). Electrically charged free electrons and (to a lesser extent, less mobile ions) resulting from the ionization of atmospheric gas atoms, interacting with radio waves (i.e. electromagnetic oscillations), can change their direction, reflecting or refracting them, and absorb their energy. As a result, when receiving distant radio stations, various effects may occur, for example, radio fading, increased audibility of distant stations, blackouts etc. phenomena.

Research methods.

The classical methods of studying the ionosphere from the Earth are reduced to pulse sounding - sending radio pulses and observing their reflections from various layers of the ionosphere with measuring the delay time and studying the intensity and shape of the reflected signals. By measuring the height of the reflection of radio pulses at various frequencies, determining the critical frequencies various areas(the critical frequency is the carrier frequency of the radio pulse, for which this region of the ionosphere becomes transparent), it is possible to determine the value of the electron concentration in the layers and the effective heights for given frequencies, and choose the optimal frequencies for given radio paths. With the development of rocket technology and the advent of the space age of artificial Earth satellites (AES) and other spacecraft, it became possible to directly measure the parameters of the near-Earth space plasma, the lower part of which is the ionosphere.

Electron density measurements carried out from specially launched rockets and along satellite flight paths confirmed and refined data previously obtained by ground-based methods on the structure of the ionosphere, the distribution of electron density with height over different regions of the Earth, and made it possible to obtain electron density values above the main maximum - the layer F. Previously, it was impossible to do this by sounding methods based on observations of reflected short-wavelength radio pulses. It has been found that in some regions of the globe there are fairly stable regions with low electron density, regular “ionospheric winds”, peculiar wave processes arise in the ionosphere that carry local ionospheric disturbances thousands of kilometers from the place of their excitation, and much more. The creation of especially highly sensitive receiving devices made it possible to carry out at the stations of pulsed sounding of the ionosphere the reception of pulsed signals partially reflected from the lowest regions of the ionosphere (station of partial reflections). The use of powerful pulse installations in the meter and decimeter wavelength ranges with the use of antennas that allow for a high concentration of radiated energy made it possible to observe signals scattered by the ionosphere at various heights. The study of the features of the spectra of these signals, incoherently scattered by electrons and ions of the ionospheric plasma (for this, stations of incoherent scattering of radio waves were used) made it possible to determine the concentration of electrons and ions, their equivalent temperature at various altitudes up to altitudes of several thousand kilometers. It turned out that the ionosphere is sufficiently transparent for the frequencies used.

The concentration of electric charges (the electron density is equal to the ion one) in the earth's ionosphere at a height of 300 km is about 106 cm–3 during the day. A plasma of this density reflects radio waves longer than 20 m, while transmitting shorter ones.

Typical vertical distribution of electron density in the ionosphere for day and night conditions.

Propagation of radio waves in the ionosphere.

The stable reception of long-range broadcasting stations depends on the frequencies used, as well as on the time of day, season and, in addition, on solar activity. Solar activity significantly affects the state of the ionosphere. Radio waves emitted by a ground station propagate in a straight line, like all types of electromagnetic waves. However, it should be taken into account that both the surface of the Earth and the ionized layers of its atmosphere serve as if the plates of a huge capacitor, acting on them like the action of mirrors on light. Reflected from them, radio waves can travel many thousands of kilometers, bending around the globe in huge jumps of hundreds and thousands of kilometers, reflecting alternately from a layer of ionized gas and from the surface of the Earth or water.

In the 20s of the last century, it was believed that radio waves shorter than 200 m were generally not suitable for long-distance communications due to strong absorption. The first experiments on long-range reception of short waves across the Atlantic between Europe and America were carried out by the English physicist Oliver Heaviside and the American electrical engineer Arthur Kennelly. Independently of each other, they suggested that somewhere around the Earth there is an ionized layer of the atmosphere that can reflect radio waves. It was called the Heaviside layer - Kennelly, and then - the ionosphere.

According to modern concepts, the ionosphere consists of negatively charged free electrons and positively charged ions, mainly molecular oxygen O + and nitric oxide NO + . Ions and electrons are formed as a result of the dissociation of molecules and the ionization of neutral gas atoms by solar X-ray and ultraviolet radiation. In order to ionize an atom, it is necessary to inform it of ionization energy, the main source of which for the ionosphere is the ultraviolet, X-ray and corpuscular radiation of the Sun.

As long as the gas shell of the Earth is illuminated by the Sun, more and more electrons are continuously formed in it, but at the same time, some of the electrons, colliding with ions, recombine, again forming neutral particles. After sunset, the production of new electrons almost stops, and the number of free electrons begins to decrease. The more free electrons in the ionosphere, the better high-frequency waves are reflected from it. With a decrease in the electron concentration, the passage of radio waves is possible only in low-frequency ranges. That is why at night, as a rule, it is possible to receive distant stations only in the ranges of 75, 49, 41 and 31 m. Electrons are distributed unevenly in the ionosphere. At an altitude of 50 to 400 km, there are several layers or regions of increased electron density. These areas smoothly transition into one another and affect the propagation of HF radio waves in different ways. Upper layer ionospheres are denoted by the letter F. Here is the highest degree of ionization (the fraction of charged particles is about 10–4). It is located at an altitude of more than 150 km above the Earth's surface and plays the main reflective role in the long-range propagation of radio waves of high-frequency HF bands. In the summer months, the F region breaks up into two layers - F 1 and F 2. The F1 layer can occupy heights from 200 to 250 km, and the layer F 2 seems to “float” in the altitude range of 300–400 km. Usually layer F 2 is ionized much stronger than the layer F one . night layer F 1 disappears and layer F 2 remains, slowly losing up to 60% of its degree of ionization. Below the F layer, at altitudes from 90 to 150 km, there is a layer E, whose ionization occurs under the influence of soft X-ray radiation from the Sun. The degree of ionization of the E layer is lower than that of the F, during the day, reception of stations of low-frequency HF bands of 31 and 25 m occurs when signals are reflected from the layer E. Usually these are stations located at a distance of 1000–1500 km. At night in a layer E ionization sharply decreases, but even at this time it continues to play a significant role in the reception of signals from stations in the bands 41, 49 and 75 m.

Of great interest for receiving signals of high-frequency HF bands of 16, 13 and 11 m are those arising in the area E interlayers (clouds) of strongly increased ionization. The area of these clouds can vary from a few to hundreds of square kilometers. This layer of increased ionization is called the sporadic layer. E and denoted Es. Es clouds can move in the ionosphere under the influence of wind and reach speeds of up to 250 km/h. In summer, in the middle latitudes during the daytime, the origin of radio waves due to Es clouds occurs 15–20 days per month. Near the equator, it is almost always present, and at high latitudes it usually appears at night. Sometimes, in years of low solar activity, when there is no passage to the high-frequency HF bands, distant stations suddenly appear with good loudness on the bands of 16, 13 and 11 m, the signals of which were repeatedly reflected from Es.

The lowest region of the ionosphere is the region D located at altitudes between 50 and 90 km. There are relatively few free electrons here. From area D long and medium waves are well reflected, and the signals of low-frequency HF stations are strongly absorbed. After sunset, ionization disappears very quickly and it becomes possible to receive distant stations in the ranges of 41, 49 and 75 m, the signals of which are reflected from the layers F 2 and E. Separate layers of the ionosphere play an important role in the propagation of HF radio signals. The impact on radio waves is mainly due to the presence of free electrons in the ionosphere, although the propagation mechanism of radio waves is associated with the presence of large ions. The latter are also of interest in the study chemical properties atmosphere, because they are more active than neutral atoms and molecules. chemical reactions flowing in the ionosphere play an important role in its energy and electrical balance.

normal ionosphere. Observations carried out with the help of geophysical rockets and satellites have given a lot of new information, indicating that the ionization of the atmosphere occurs under the influence of broad-spectrum solar radiation. Its main part (more than 90%) is concentrated in the visible part of the spectrum. Ultraviolet radiation with a shorter wavelength and more energy than violet light rays is emitted by hydrogen in the inner part of the Sun's atmosphere (chromosphere), and X-ray radiation, which has even higher energy, is emitted by the gases of the Sun's outer shell (corona).

The normal (average) state of the ionosphere is due to constant powerful radiation. Regular changes occur in the normal ionosphere under the influence of the daily rotation of the Earth and seasonal differences in the angle of incidence of the sun's rays at noon, but unpredictable and abrupt changes in the state of the ionosphere also occur.

Disturbances in the ionosphere.

As is known, powerful cyclically repeating manifestations of activity occur on the Sun, which reach a maximum every 11 years. Observations under the program of the International Geophysical Year (IGY) coincided with the period of the highest solar activity for the entire period of systematic meteorological observations, i.e. from the beginning of the 18th century. During periods of high activity, the brightness of some areas on the Sun increases several times, and the power of ultraviolet and X-ray radiation increases sharply. Such phenomena are called solar flares. They last from several minutes to one or two hours. During a flare, solar plasma (mostly protons and electrons) is erupted, and elementary particles rush into outer space. The electromagnetic and corpuscular radiation of the Sun at the moments of such flares has a strong effect on the Earth's atmosphere.

The initial reaction is noted 8 minutes after the flash, when intense ultraviolet and X-ray radiation reaches the Earth. As a result, ionization sharply increases; x-rays penetrate the atmosphere to the lower boundary of the ionosphere; the number of electrons in these layers increases so much that the radio signals are almost completely absorbed ("extinguished"). Additional absorption of radiation causes heating of the gas, which contributes to the development of winds. Ionized gas is an electrical conductor, and when it moves in the Earth's magnetic field, the dynamo effect appears and arises electricity. Such currents can, in turn, cause noticeable perturbations of the magnetic field and manifest themselves in the form of magnetic storms.

The structure and dynamics of the upper atmosphere is essentially determined by thermodynamically nonequilibrium processes associated with ionization and dissociation solar radiation, chemical processes, excitation of molecules and atoms, their deactivation, collision and other elementary processes. In this case, the degree of nonequilibrium increases with height as the density decreases. Up to altitudes of 500–1000 km, and often even higher, the degree of nonequilibrium for many characteristics of the upper atmosphere is sufficiently small, which allows one to use classical and hydromagnetic hydrodynamics with allowance for chemical reactions to describe it.

The exosphere is the outer layer of the Earth's atmosphere, starting at altitudes of several hundred kilometers, from which light, fast-moving hydrogen atoms can escape into outer space.

Edward Kononovich

Literature:

Pudovkin M.I. Fundamentals of solar physics. St. Petersburg, 2001
Eris Chaisson, Steve McMillan Astronomy today. Prentice Hall Inc. Upper Saddle River, 2002
Online materials: http://ciencia.nasa.gov/

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