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 various functions, contains the oxygen necessary for life, protects from solar rays and external agents such as meteorites and asteroids.
The composition of the atmosphere is mostly nitrogen, but it is also made up of oxygen and has a very small concentration of other gases such as water vapor, argon, and carbon dioxide.
Although it may not seem like it, the air is heavy, and the air in the upper layers pushes the air in the lower layers, causing a greater concentration of air in the lower layers.
This phenomenon is known as atmospheric pressure. Higher up in the atmosphere, it becomes less dense.
Marking the limit of the end of the atmosphere about 10,000 km high. 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 is located between the surface of the earth up 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 meteorological phenomena occur.
The stratosphere is the layer that extends from 10-15 km in height to 40-45 km. In this layer is the ozone layer, at a height of about 40 km, and it is what protects us from the harmful rays of the sun.
The mesosphere is the thinnest layer of the atmosphere, which extends up to a height of 85-90 km high. This layer is very important, since it is the one that slows the small meteorites that crash against the terrestrial sky.
The thermosphere is the widest layer of the atmosphere, with a temperature that can reach thousands of degrees Celsius, it is packed with materials charged with the energy of the sun.
The exosphere is the layer furthest from the Earth's surface. This extends from 600-800 km to 9,000-10,000.
The end of the exosphere is not well defined, since in this layer, which is in contact with outer space, the atoms escape, making their limitation very difficult. The temperature in this layer practically does not vary, and the physicochemical properties of the air here disappear.
Exosphere: the layer in which gravity disappears
The exosphere is the transit zone between the atmosphere and outer space. Here the polar-orbiting meteorological satellites are suspended in the air. They are found in this layer of the atmosphere since the effect of gravity is almost non-existent.
The density of air is almost negligible also due to its low gravity, and atoms escape since gravity does not push them towards the earth's surface.
In the exosphere there is also the flow or plasma, which from the outside looks like the Van Allen Belts.
The exosphere is made up of plasma materials, where the ionization of the molecules forms a magnetic field, which is why it is also known as the magnetosphere.
Although in many places the name exosphere or magnetosphere is used interchangeably, 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 deflected towards the magnetic poles causing northern and southern lights. 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, with the exception of 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, makes the air particles of the lighter gases have a sufficient speed to escape into outer space.
Since the magnetic field to which they are subjected increases their speed, and the gravitational force of the earth is not enough to stop these particles.
By not suffering the effect of gravity, air molecules are more dispersed than in other layers of the atmosphere. By having a lower density, the collisions that occur between air molecules are much rarer.
Therefore, the molecules that are in the highest part, have greater speed, and can escape from 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. hydrogen atoms have a speed of 5 km per second on average.
But there are areas where hydrogen atoms can reach 10.8Km / s, which is the speed necessary to overcome gravity at that altitude.
As the speed also depends on the mass of the molecules, the greater the mass, the lower the speed they will have, and there may be particles in the upper part of the exosphere that do not reach the necessary speed to escape Earth's gravity, despite being bordering outer space.
References
- DUNGEY, JW The structure of the exosphere or adventures in velocity space. Geophysics, The Earth's Environment, 1963, vol. 503.
- SINGER, SF 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 model current sheet, 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.
- DOMINGUEZ, Hector. Our atmosphere: how to understand climate change. LD Books, 2004.
- SALVADOR DE ALBA, Angel. The wind in the upper atmosphere and its relationship with the sporadic E layer. Complutense University of Madrid, Publications Service, 2002.
- LAZO, Welcome; CALZADILLA, Alexander; ALAZO, Katy. Solar Wind-Magnetosphere-Ionosphere Dynamic System: Characterization and Modeling. Prize of the Academy of Sciences of Cuba, 2008.