The layer of the atmosphere in which gravity disappears is the exosphere. The atmosphere is the layer of gases that surrounds the Earth.
It fulfills several functions, it contains the necessary oxygen for the life, protects of the solar rays and of external agents like meteorites and asteroids.
The composition of the atmosphere is mostly nitrogen, but it is also composed of oxygen and has a very small concentration of other gases such as water vapor, argon and carbon dioxide.
Although it does not seem like it, the air weighs, and the air that is in the upper layers pushes that of the lower layers, causing that there is greater concentration of air in the inferior layers.
This phenomenon is known as atmospheric pressure. The higher it is in the atmosphere, the more it becomes less dense.
Marking the limit of the end of the atmosphere to about 10,000 km in height. What is known as the Karman Line.
Layers of the atmosphere
The atmosphere is divided into five layers, the troposphere, the stratosphere, the mesosphere, the thermosphere and the exosphere.
The troposphere is the layer that lies between the surface of the earth to a height of between 10 and 15 km. It is the only layer of the atmosphere that allows the development of life, and where the meteorological phenomena occur.
The stratosphere is the layer that extends from 10-15 km in height to 40-45. In this layer is the ozone layer, at a height of about 40 km, and is the one that protects us from the harmful rays of the sun.
The mesosphere is the thinnest layer of the atmosphere, which extends to a height of 85-90 km in height. This layer is very important, since it is the one that stops the small meteorites that crash against the terrestrial sky.
The thermosphere is the broadest layer of the atmosphere, with a temperature that can reach thousands of degrees Celsius, is full of materials charged with the energy of the sun.
The exosphere is the furthest layer of the earth's surface. This extends from 600-800 km to 9,000-10,000.
The end of the exosphere is not well defined, because in this layer, which is in contact with outer space, the atoms escape, making it very difficult to limit. The temperature in this layer practically does not vary, and the physical-chemical properties of the air disappear here.
Exosphere: the layer in which gravity disappears
The exosphere is the transit zone between the atmosphere and outer space. Here polar meteorological satellites are suspended in the air. They are in this layer of the atmosphere since the effect of gravity is almost non-existent.
The density of the air is almost negligible because of the low gravity it has, and the atoms escape because gravity does not push them towards the Earth's surface.
In the exosphere is also the flow or plasma, which from the outside looks like the Van Allen Belts.
The exosphere is constituted by plasmatic materials, where the ionization of the molecules forms a magnetic field, reason why also it is known like magnetosfera.
Although in many places the name of exosphere or magnetosphere is used indistinctly, a distinction must be made between the two. The two occupy the same place, but the magnetosphere is contained within the exosphere.
The magnetosphere is formed by the interaction of the earth's magnetism and the solar wind and protects the earth from solar radiation and cosmic rays.
The particles are diverted to the magnetic poles causing aurora borealis and austral. The magnetosphere is caused by the magnetic field produced by the iron core of the earth, which has electrically charged materials.
Almost all the planets in the solar system, except for Venus and Mars, have a magnetosphere that protects them from the solar wind.
If the magnetosphere did not exist, the sun's radiation would reach the surface causing the loss of the planet's water.
The magnetic field formed by the magnetosphere causes the air particles of the lighter gases to have enough velocity to escape into outer space.
Since the magnetic field to which they are subjected increases its speed, and the gravitational force of the earth is not enough to stop these particles.
Not having the effect of gravity, the air molecules are more dispersed than in other layers of the atmosphere. As it has a lower density, collisions occurring between air molecules are much rarer.
Therefore, the molecules that are in the higher part, have higher speed, and can escape the gravity of the earth.
To give an example and make it easier to understand, in the upper layers of the exosphere where the temperature is around 700ºC. The hydrogen atoms have a speed of 5Km per second on average.
But there are areas where hydrogen atoms can reach 10.8 km / s, which is the speed necessary to overcome gravity at that altitude.
As velocity also depends on the mass of the molecules, the more mass the less mass they will have, and there may be particles in the upper part of the exosphere that do not reach the velocity necessary to escape terrestrial gravity, Bordering on outer space.
References
- DUNGEY, J. W. The structure of the exosphere or adventures in velocity space. Geophysics, The Earth's Environment , 1963, vol. 503.
- SINGER, S. F. Structure of the earth's exosphere. Journal of Geophysical Research , 1960, vol. 65, no. 9, p. 2577-2580.
- BRICE, Neil M. Bulk motion of the magnetosphere. Journal of Geophysical Research , 1967, vol. 72, no. 21, p. 5193-5211.
- SPEISER, Theodore Wesley. Particle trajectories in a current model, based on the open model of the magnetosphere, with applications to auroral particles. Journal of Geophysical Research , 1965, vol. 70, no. 7, p. 1717-1728.
- . Our Atmosphere: Understanding Climate Change . LD Books, 2004.
- SALVADOR DE ALBA, Ángel. The wind in the upper atmosphere and its relation with the sporadic E layer . Universidad Complutense de Madrid, Publications Service, 2002.
- LAZO, Welcome; CALZADILLA, Alexander; ALAZO, Katy. Dynamic System Wind Solar-Magnetosphere-Ionosphere: Characterization and Modeling. Prize of the Academy of Sciences of Cuba , 2008.