What advantages does the ionosphere offer people?

The atmosphere as the shell of the earth

Seen from space, the earth appears blue with scattered white fields, the clouds.

Fig.1: The protective atmosphere is very thin compared to the diameter of the earth.

The blue color is caused by the gas layer, the air, that envelops the earth. In the atmosphere, the shorter-wave blue sunlight is strongly scattered in all directions, while the longer-wave red light can largely penetrate the atmosphere. The atmosphere is of crucial importance for the existence of life on earth because it is where the physical processes take place, including determine the weather. In addition, it is part of vital cycles.

The climate is the totality of meteorological phenomena and characterizes the middleStatus the atmosphere anywhere on the surface of the earth. The earth's climate is the result of physical processes that are set in motion in the atmosphere by the action of the sun. The course of these processes is essentially determined by the rotation of the earth (Coriolis force), the geographical latitude, the distribution of land and sea, ocean currents, but also by the terrain surface, vegetation, buildings and other geophysical factors.

Functions of the atmosphere

The atmosphere has a number of vital functions by being

  1. protects living beings from harmful or deadly radiation from space (filter for UV and X-ray radiation from the sun),
  2. lets vital sunlight through to the surfaces of the continents and oceans (energy source),
  3. protects against rapid cooling and overheating (e.g. heat balance between day and day),
  4. the average surface temperature of the earth of approx. +15 ° C, compared to approx. -18 ° C otherwise, enables
  5. Energy (sensible heat of the air and latent heat of the water vapor) transported from areas near the equator to middle and higher latitudes),
  6. Water vapor moisture is transported and distributed through the dynamic processes of general circulation, which determines the distribution of precipitation,
  7. forms the main storage for nitrogen,
  8. represents a reservoir for carbon dioxide and oxygen.
  9. is involved in various vital material cycles,
  10. natural and anthropogenic (man-made) emissions that are converted and broken down in the atmosphere through oxidation, reactions with radicals and photolysis
  11. protects against smaller meteorites, which burn up due to the great friction when entering the atmosphere and thus do not reach the earth's surface.

Building the atmosphere

General
The total air mass of the earth's atmosphere is 5.13 · 1015 t, d. H. three hundredths of the water mass of the oceans or approx. one millionth of the mass of the earth. It surrounds the earth as a thin shell. The layer thickness of the atmosphere up to the upper limit of the stratosphere (50 km) is less than 1% of the earth's radius (6,378 km). The air pressure at a height of 50 km is around two thousandths of the pressure on the earth's surface (around 2 hPa).

The existence of the gaseous atmosphere around the earth is based on the fact that there is an equilibrium between gravitation and the proper movements of the molecules or atoms.

Like all other masses, gravitation also holds the gases to the earth. As a result of the gas particles' own movements, they would otherwise quickly evaporate into space through diffusion. Gas molecules with small masses reach higher speeds at low pressures - for example above the thermosphere - and at the same temperature and thus have a greater probability of escaping into space against the gravitational pull than gas molecules with large masses.

With increasing altitude, the air pressure, and with it the density, steadily decrease. near the earth according to an exponential function (the barometric altitude formula), until the atmosphere gradually (magnitude: 1000 km) changes into the material-poor space. The barometric height formula derived from the energy distribution for the movement of the gas molecules is:
 

pH = pho · E-h / ho with hO = 8.0 km

It means:
pH = Pressure at height h
pho = Pressure at height hO = 0 m (NN) and 273 K
pho = 1013 hPa
h = altitude in km above sea level

The half-height of the exponential function is 5.5 km. That means: At constant temperature, the pressure decreases every 5.5 km to about half of its previous value. For more precise calculations, the temperature has to be taken into account. At an altitude of 18 km the air pressure is only a tenth, at 55 km a thousandth and at 110 km only a millionth of the land value.

Above the thermosphere, in the exosphere, the density becomes extremely low; Air pressure and density are proportional to each other. Gas particles, strictly speaking only the lightest gases hydrogen and helium, can do so because of their high concentration
medium kinetic energy and its low mass escape from the earth's gravitational field.

At an altitude of 3600 km, the atmosphere (exosphere) is already so thin that the geostationary satellites located above the equator can be kept practically frictionless for years without correction.
 

Structure of the atmosphere

There are multiple possibilities. to subdivide the atmosphere based on its different properties and processes. Classifications according to:

  • the temperature profile in the troposphere, stratosphere, thermosphere and exosphere,
  • the composition of the air in the homosphere and heterosphere and
  • the degree of ionization of the gas particles in the neutrosphere and ionosphere.
The troposphere is particularly important for life on earth. Therefore, the explanations in the following chapters are mainly limited to the troposphere.
 

Breakdown according to the composition
The percentage composition of the atmosphere with chemically stable components, such as molecular nitrogen, carbon dioxide, noble gases and almost also oxygen, is almost uniform in the lower layers up to a height of 80 km due to the mixing of the horizontal and vertical air movements (homosphere). Most of the mass of the atmosphere is in the homosphere, namely around 100,000 times as much as in the entire part of the gas envelope above it.

In the upwardly adjoining heterosphere the division of the gases begins due to their different molar masses. Ultimately, with increasing altitude, only the lightest gases, hydrogen and helium, remain.
 

Breakdown according to temperature
In addition to the well-known horizontal temperature distribution (at the equator there is a different temperature than at the poles), the atmosphere also shows a pronounced vertical temperature distribution, which is determined by various interconnected physical and chemical processes and is of great importance for the transport of air and its components is.
 

Fig.2: Vertical temperature profile and the resulting stratification of our earth.

The vertical distribution of temperature shows a characteristic curve that can be observed everywhere on earth. Due to the temperature distribution, the atmosphere can be divided into five layers with the following mean altitude values:
 

Troposphere
stratosphere
Mesosphere
Thermosphere
Exosphere
0 to 12 km
12 to 50 km
50 to 85 km
85 to 500 km
over 500 km

The turning points of the vertical temperature curve that can be seen in Fig. 2 are shown in ascending order as

  • Tropopause
  • Stratopause
  • Mesopause
designated.

Above the tropopause and mesopause, warmer air lies above colder air, as is also observed in the inversion weather conditions that occasionally occur near the ground, in which the exchange between warm soil air and cold air above is also very difficult. So rising air in the troposphere cools down strongly (by 6.5 ° C to 1000 m) and then - according to the greatly simplified depiction - cannot get into the warmer stratosphere above.

The location of the tropopause is very much dependent on the geographical latitude and the season. It reaches its maximum of 17-18 km above the tropics. At the poles it is only about 8 km. The troposphere contains 80% of the mass of the entire atmosphere. It is the layer in which the weather takes place with the formation of clouds and precipitation as well as a lively mixture. The troposphere contains almost all of the water vapor in the atmosphere. In its lowest layer, the 1 to 2.5 km thick planetary boundary layer (see Fig. 4), the influence of the earth's surface causes strong changes in the meteorological parameters of temperature, wind and humidity. At the height of the tropopause, the temperature is around -60 ° C. The so-called jet streams also appear here as relatively narrow bands with very high wind speeds (up to 500 km / h). In the area of ​​these jet currents, important processes are constantly taking place that lead to vertical splitting, dissolution or new formation of the tropopause.

Above the tropopause, in the stratosphere, the temperature rises again. This warming is mainly caused by the ozone present there, which absorbs the short-wave portion of solar radiation. The ozone layer is therefore of the utmost importance for life on earth. The stratosphere is practically cloud-free. This is because, due to the extremely low temperatures in the tropopause, the transport of water vapor from the troposphere into the stratosphere is so low that the stratosphere contains practically no water vapor.

The stratosphere can be divided into

  • a lower stratosphere with a roughly constant temperature around -56 ° C (isothermal energy) and
  • an upper stratosphere above 20 km altitude, in which the temperature as a result of the absorption of radiation can reach values ​​of

  • on average increases to 0 ° C. Because of this temperature increase with altitude, there is limited vertical movement.
The begins above the stratosphere Mesosphere. In the next 30 km the temperature drops from around 0 ° C to almost -100 ° C.

The joins the mesosphere Thermosphere at. Because of the low particle density, practically no temperatures can be determined in it, only radiation energies.

The begins above 500 km Exospherein which the space stations are positioned.

Breakdown according to the degree of ionization
Taking into account the ionization state of the air, the atmosphere can also be divided into a neutrosphere (up to approx. 80 km altitude) and an ionosphere (above 80 km to approx. 1000 to 2000 km altitude). The thermosphere lies within the ionosphere.

Above 80 km, the atmosphere is greatly changed under the influence of ultraviolet solar radiation or high-energy cosmetic radiation.

The gases that appear in the deep atmosphere as diatomic and polyatomic molecules are partially split into atoms and further into ions and electrons in the ionosphere by the high-energy solar radiation (UV and cosmic radiation). H. ionized. The energy-rich rays, which are deadly or harmful for all life, are filtered out. This is the only way life on earth is possible. Due to the ionization of the various components of the atmosphere by radiation from very different spectral ranges, several layers of electron concentration form in the high atmosphere.

The ionosphere is divided into intermediate layers that can reflect electromagnetic waves. These layers of the ionosphere are of great importance for the worldwide propagation of radio (short) waves.


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