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The Ionosphere

March 19, 2021

Benyamin Amiri

By: Benyamin Amiri

The Ionosphere

Reading time: 9 min

    Content List

In the Earth Atmosphere Composition and Structure lesson, we examined the ionosphere in general, but in this lesson, we will study the ionosphere more comprehensively.

Ionosphere definition

The regions of the Earth’s atmosphere where relatively large numbers of electrically charged atoms and molecules are found are called the ionosphere.

As you know X-rays and ultraviolet light that are produced by the sun, constantly collide with gas molecules and atoms in the Earth’s upper atmosphere, therefore these collisions cause some molecules and atoms to lose their electrons, forming electrically charged ions and free electrons.

Areas with higher concentrations of free ions and electrons are formed at three different altitudes and are known as a group called the ionosphere.

Ionosphere layer

The ionosphere has three main regions: D layer, E layer, and F layer.

There is also a C region below other regions, but the level of ionization is very low, hence it is mentioned rarely and we are not cover it in this article.

Ionosphere altitude

The height of the ionosphere varies during a day and from season to season. Layer D is the lowest and closest layer to the earth, starting about 60 or 70 km (37 or 43 miles) above the Earth’s surface and continuing about 90 km (56 miles) above the Earth’s surface.

The next layer is E, which starts from about 90 km or 100 km (56 or 62 miles) above the ground and extends about 120 km or 150 km (75 or 93 miles).

The highest ionosphere layer is F, which starts about 200 km (124 miles) above the Earth’s surface and sometimes extends about 600 km (372 miles).

It should be noted, like the layers of the Earth’s atmosphere, ionosphere regions are not considered as separate layers, but instead, they are ionized regions located in the layers of the Earth’s atmosphere.

The D region is usually formed in the upper part of the mesosphere, and E region is usually formed in the lower part of the thermosphere, and finally, the F region is formed in the upper part of the thermosphere.

The number of ionized particles, the height, and the existence of the ionosphere regions are not constant over time and are variable. The ionosphere is very different during the day than at night.

During the day, ultraviolet light and X-rays continuously provide the needed energy to separate electrons from molecules and atoms. Also, at the same time, some ions and electrons collide and return to normal and neutral molecules and atoms.

During the day, due to the presence of sunlight, more ions are produced than the ions that are lost, so we see an increase in ions in the three ionosphere regions.

During the day, due to the presence of sunlight, more ions are produced compared to ions that return to normal form, so ions increase in the three ionosphere regions.

During the night, due to the lack of sunlight, the ions combine with the electrons thus their number decreases rapidly until the D region disappears completely and the E region becomes very weak. But every morning, due to the presence of X-rays and ultraviolet light from the sun in the D and E regions, the ions increase again.

ionosphere layer

Ionosphere temperature

In the structure and composition of the Earth’s atmosphere, we examined the temperature in different layers of the atmosphere. As we know, the ionosphere starts from the upper part of the mesosphere and extends to the top of the thermosphere.

Consequently, the ionosphere has dissimilar temperatures in different parts of the Earth’s atmosphere, so that in the upper part of the mesosphere its temperature reaches -90 degrees Celsius (-130 Fahrenheit) and in the upper part of the thermosphere its temperature reaches about 2000 degrees Celsius (3632 Fahrenheit).

Why is the ionosphere important?

The ionosphere is useful in many ways. The ionosphere protects organisms and living things on the earth by absorbing ultraviolet light. Also, the ionosphere reflects radio waves emitted from the earth and bounces them back toward the earth.

Why does the ionosphere reflect radio waves

 

Why does the ionosphere reflect radio waves?

The ionosphere contains large amounts of free electrons that affect the propagation of radio waves. When high frequency (HF) radio waves hit free electrons in the ionosphere cause them to vibrate and re-radiate energy with the same frequency to the Earth. This ionosphere feature has long been used to enable long-distance radio communications.

 

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