Why is there a high temperature in the thermosphere. Atmosphere

The upper part of the atmosphere, above the mesosphere, is characterized by very high temperatures and is therefore called the thermosphere. However, two parts are distinguished in it: the ionosphere, which extends from the mesosphere to heights of the order of a thousand kilometers, and the outer part lying above it - the exosphere, passing into the earth's corona.

The air in the ionosphere is extremely rarefied. We have already indicated that at altitudes of 300-750 km its average density is about 10-8-10-10 g/m3. But even at such a low density, each cubic centimeter air at an altitude of 300 km still contains about one billion (109) molecules or atoms, and at an altitude of 600 km - more than 10 million (107). This is several orders of magnitude greater than the content of gases in interplanetary space.

The ionosphere, as the name itself says, is characterized by a very strong degree of air ionization - the content of ions here is many times greater than in the underlying layers, despite the strong overall rarefaction of the air. These ions are mainly charged oxygen atoms, charged nitric oxide molecules, and free electrons. Their content at altitudes of 100-400 km is about 1015-106 per cubic centimeter.

In the ionosphere, there are several layers, or regions, with maximum ionization, especially at altitudes of 100-120 km (layer E) and 200-400 km (layer F). But even in the intervals between these layers, the degree of ionization of the atmosphere remains very high. The position of the ionospheric layers and the concentration of ions in them change all the time. Sporadic accumulations of electrons with a particularly high concentration are called electron clouds.

The electrical conductivity of the atmosphere depends on the degree of ionization. Therefore, in the ionosphere, the electrical conductivity of air is generally 1012 times greater than that of the earth's surface. Radio waves experience absorption, refraction and reflection in the ionosphere. Waves longer than 20 m cannot pass through the ionosphere at all: they are already reflected by electron layers of low concentration in the lower part of the ionosphere (at altitudes of 70-80 km). Medium and short waves are reflected by the overlying ionospheric layers.

It is due to reflection from the ionosphere that long-range communication at short waves is possible. Multiple reflections from the ionosphere and the earth's surface allows short waves to zigzag to propagate over long distances, bending around the surface globe. Since the position and concentration of the ionospheric layers are continuously changing, the conditions for absorption, reflection and propagation of radio waves also change. Therefore, reliable radio communication requires continuous study of the state of the ionosphere. Observations on the propagation of radio waves are precisely the means for such research.

In the ionosphere there are auroras and close to them in nature, the glow of the night sky - a constant luminescence of atmospheric air, as well as sharp fluctuations magnetic field- ionospheric magnetic storms.

Ionization in the ionosphere owes its existence to the action of ultraviolet radiation from the Sun. Its absorption by atmospheric gas molecules leads to the appearance of charged atoms and free electrons, as discussed above. Fluctuations in the magnetic field in the ionosphere and auroras depend on fluctuations solar activity. Changes in solar activity are associated with changes in the flux of corpuscular radiation coming from the Sun into the Earth's atmosphere. Namely, corpuscular radiation is of fundamental importance for these ionospheric phenomena.

The temperature in the ionosphere increases with height to very high values. At altitudes of about 800 km it reaches 1000°.

Speaking about the high temperatures of the ionosphere, they mean that particles of atmospheric gases move there at very high speeds. However, the air density in the ionosphere is so low that a body located in the ionosphere, such as a flying satellite, will not be heated by heat exchange with air. Temperature regime satellite will depend on the direct absorption of solar radiation by it and on the return of its own radiation to the surrounding space. The thermosphere is located above the mesosphere at an altitude of 90 to 500 km above the Earth's surface. The gas molecules here are highly scattered, they absorb x-rays (X rays) and the short-wave part of ultraviolet radiation. Because of this, the temperature can reach 1000 degrees Celsius.

the thermosphere basically corresponds to the ionosphere, where ionized gas reflects radio waves back to the Earth - this phenomenon makes it possible to establish radio communications.

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Flying in the thermosphere

Due to the extreme thinness of the air, flights above the Karman line are possible only along ballistic trajectories. All manned orbital flights (except flights to the Moon) take place in the thermosphere, mainly at altitudes from 200 to 500 km - below 200 km the decelerating effect of air is strongly affected, and above 500 km radiation belts extend, which have a harmful effect on people.

Unmanned satellites also mostly fly in the thermosphere - putting a satellite into a higher orbit requires more energy, and for many purposes (for example, for remote sensing of the Earth), low altitude is preferable.

The high air temperature in the thermosphere is not terrible for aircraft, because due to the strong rarefaction of air, it practically does not interact with the skin. aircraft, that is, the air density is not enough to heat the physical body, since the number of molecules is very small and the frequency of their collisions with the ship's hull (respectively, the transfer of thermal energy) is small. Thermosphere research is also carried out with the help of suborbital geophysical rockets.

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. In the troposphere, turbulence and convection are highly developed, clouds appear, cyclones and anticyclones develop. Temperature decreases with altitude with an average vertical gradient of 0.65°/100 m

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 (lower layer of the stratosphere) and its increase in the 25-40 km layer from −56.5 to 0.8 °С are characteristic ( upper layer stratosphere or inversion region). 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

The mesosphere begins at an altitude of 50 km and extends up to 80-90 km. The temperature decreases with height with an average vertical gradient of (0.25-0.3) ° / 100 m. energy process is radiant heat transfer. Complex photochemical processes involving free radicals, vibrationally excited molecules, etc., cause atmospheric luminescence.

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. The Karmana line is located at an altitude of 100 km above sea level.

Earth's atmosphere boundary

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 influence of ultraviolet and x-ray 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, 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)

Atmospheric layers up to a height of 120 km

Exosphere - scattering zone, the outer part of the thermosphere, located above 700 km. The gas in the exosphere is very rarefied, and hence its particles leak into interplanetary space (dissipation).

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 weights, 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. but kinetic energy 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 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 electrical properties The atmosphere is divided into the neutrosphere and the ionosphere. It is currently believed that the atmosphere extends to an altitude of 2000-3000 km.

Depending on the composition of the gas in the atmosphere, homosphere and heterosphere are distinguished. The heterosphere is an area where gravity has an effect on 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 the turbopause and lies at an altitude of about 120 km.

It starts at an altitude of 80-90 km and extends up to 800 km. The air temperature in the thermosphere fluctuates at different levels, increases rapidly and discontinuously and can vary from 200 to 2000 K, depending on the degree of solar activity. The reason is the absorption of ultraviolet radiation from the Sun at altitudes of 150-300 km, due to the ionization of atmospheric oxygen. In the lower part of the thermosphere, the temperature increase is largely due to the energy released during the combination (recombination) of oxygen atoms into molecules (in this case, the energy of solar UV radiation, absorbed earlier during the dissociation of O 2 molecules, is converted into the energy of the thermal motion of particles). At high latitudes important source heat in the thermosphere - Joule heat released by electric currents of magnetospheric origin. This source causes significant but uneven heating of the upper atmosphere in subpolar latitudes, especially during magnetic storms.

Flying in the thermosphere

Due to the extreme thinness of the air, flights above the Karman line are possible only along a ballistic trajectory. All manned orbital flights (with the exception of the flights of American astronauts to the Moon) take place in the thermosphere, mainly at altitudes from 200 to 500 km - below 200 km the decelerating effect of air is strongly affected, and above 500 km radiation belts extend that have a harmful effect on people.

Unmanned satellites also mostly fly in the thermosphere - putting a satellite into a higher orbit requires more energy, and for many purposes (for example, for remote sensing of the Earth), low altitude is preferable.

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See what "Thermosphere" is in other dictionaries:

Thermosphere… Spelling Dictionary

thermosphere- Area of ​​the upper atmosphere at altitudes of 100 500 km with a positive temperature gradient. [GOST 25645.113 84] thermosphere The layer of the planet's atmosphere lying above the mesosphere, characterized by an increase in temperature with height, gradually slowing down and ... ... Technical Translator's Handbook

Atmospheric layer above the mesosphere from heights of 80-90 km, the temperature in which rises to heights of 200-300 km, where it reaches values ​​of the order of 1500 K, after which it remains almost constant up to high altitudes ... Big Encyclopedic Dictionary

THERMOSPHERE, a shell of light gases between the MESOSPHERE and EXOSPHERE, at an altitude of 100 km to 400 km from the Earth's surface. As the altitude in the thermosphere increases, the temperature increases uniformly... Scientific and technical encyclopedic dictionary Geographic Encyclopedia

Atmospheric layer above the mesosphere from heights of 80-90 km, the temperature in which rises to heights of 200-300 km, where it reaches values ​​of the order of 1500 K, after which it remains almost constant up to high altitudes. * * * THERMOSPHERE THERMOSPHERE, the atmospheric layer above… … encyclopedic Dictionary

- (see thermo ... + sphere) upper layers of the atmosphere, above 80 km, in which the temperature increases with altitude to very high values ​​(1500 ° C at altitudes of 200 300 km or more). New dictionary foreign words. by EdwART, 2009. thermosphere (te), s, zh. (… Dictionary of foreign words of the Russian language

Mesosphere

Located above the stratosphere, it is a shell in which, up to a height of 80-85 km, the temperature drops to the minimum for the atmosphere as a whole. record breaking low temperatures down to -110° were registered by meteorological rockets launched from the US-Canadian installation at Fort Churchill (Canada). The upper limit of the mesosphere (mesopause) approximately coincides with the lower limit of the region of active absorption of the X-ray and the shortest wavelength ultraviolet radiation of the Sun, which is accompanied by heating and ionization of the gas.

In the polar regions in summer, cloud systems often appear in the mesopause, which occupy a large area, but have little vertical development. Such clouds glowing at night often make it possible to detect large-scale undulating air movements in the mesosphere. The composition of these clouds, sources of moisture and condensation nuclei, dynamics and relationship with meteorological factors are still insufficiently studied.

Thermosphere

It is a layer of the atmosphere in which the temperature rises continuously. Its power can reach 600 km. The pressure and, consequently, the density of a gas constantly decrease with height. Near the earth's surface, 1 m3 of air contains approx. 2.5×1025 molecules, at a height of approx. 100 km, in the lower layers of the thermosphere - approximately 1019, at an altitude of 200 km, in the ionosphere - 5×1015 and, according to calculations, at an altitude of approx. 850 km - approximately 1012 molecules. In interplanetary space, the concentration of molecules is 108-109 per 1 m3.

At a height of approx. 100 km, the number of molecules is small, and they rarely collide with each other. The average distance traveled by a chaotically moving molecule before colliding with another similar molecule is called its mean free path. The layer in which this value increases so much that the probability of intermolecular or interatomic collisions can be neglected is located on the boundary between the thermosphere and the overlying shell (exosphere) and is called the thermal pause. The thermopause is located approximately 650 km from the earth's surface.

At a certain temperature, the speed of a molecule's movement depends on its mass: lighter molecules move faster than heavy ones. In the lower atmosphere, where the free path is very short, there is no noticeable separation of gases according to their molecular weight, but it is expressed above 100 km. In addition, under the influence of ultraviolet and X-ray radiation from the Sun, oxygen molecules break down into atoms, the mass of which is half the mass of the molecule. Therefore, as we move away from the Earth's surface, atomic oxygen becomes increasingly important in the composition of the atmosphere and at an altitude of approx. 200 km becomes its main component. Higher, at a distance of about 1200 km from the Earth's surface, light gases - helium and hydrogen - predominate. Of these it consists outer shell atmosphere. This separation by weight, called diffuse separation, resembles the separation of mixtures using a centrifuge.

Exosphere

exosphere called the outer layer of the atmosphere, allocated on the basis of changes in temperature and properties of neutral gas. Molecules and atoms in the exosphere revolve around the Earth in ballistic orbits under the influence of gravity. Some of these orbits are parabolic and similar to the trajectories of projectiles. Molecules can revolve around the Earth and in elliptical orbits, like satellites. Some molecules, mainly hydrogen and helium, have open trajectories and go into outer space.