F1-Layer of Earth’s Atmosphere

With the neutral composition of earth’s atmosphere in mind, we may split it into three major regions: the homosphere up to an altitude of approximately 90 km (55 miles), the ionosphere up to an altitude of around 600 km (370 miles), and the exosphere beyond 600 km (370 miles).

The term ION refers to the ionosphere, which means “ionised atmosphere.” High up in our atmosphere, probably between 60 km (38 miles) and 500 km (310 miles) or even higher, we come across regions of rarefied diffused gases, which are rarefied gases that have been diffused. At these altitudes, the pressure is low enough that ions can form and transit freely for a long period without clashing and recombining into neutral atoms, allowing for the formation of ions.

What is the source of the creation of ions? 

With a power density of 1370 Watts per square metre at the farthest reaches of the earth’s environment, solar radiation strikes the atmosphere, producing the Solar Constant. This is a value that has been used to describe the power density of solar radiation on the earth’s environment. This high amount of radiation is dispersed throughout a wide spectrum, spanning from radio frequencies to infrared, visible light, ultraviolet, and X-rays. 

It can be measured in millimetres per second. Other factors contribute to the sun’s electromagnetic radiation, such as cosmic rays and solar wind particles, but their influence is negligible compared to the sun’s electromagnetic radiation. Occasionally, the influence of these beings can only be seen at nighttime.

Solar radiation occurs in various wavelengths, including ultraviolet, extreme ultraviolet, soft and hard X-rays, and Lyman alpha. All of these rays and cosmic rays from deep space go from the sun to the earth and into our planet’s surrounding atmosphere and atmosphere. Depending on their wavelength, some of these radiations are more dominating, brighter, or powerful than others. 

Various peaks in ionisation will be visible in the ionosphere at various altitudes due to the varied dominance and strength of the ionising radiation. In the ionosphere, the density and temperature of the rarefied gases at different altitudes and the diversity of radiation are the primary factors that contribute to the creation of distinct kinds of interstellar ionised layers at different altitudes.

Once above 1000 kilometres in altitude, the radiation only contacts a small but dense population of gas particles in the high atmosphere, where the radiation first encounters sunlight. The radiation is sweeping down into the lower atmosphere, where it comes into contact with a sparse population of gas particles. This is where the ionisation process has a practically negligible effect on radiation absorption. The rays interact with more gas atoms and molecules as they go deeper into the atmosphere. Thus, electron density rises due to ionisation, which is the outcome.

In the range of around 140 to 350 kilometres in altitude, the UV and EUV photons play the most important role in ionisation. They combine to form the F-layer, a layer of high electron density. During the day, the F-region is frequently divided into two distinct layers, which are referred to as the F2 and the F1 areas. 

The F2 region is the most dominating and is higher above the F1 region than the rest of the regions. The F2 region is the most essential of the two F-regions for radio communications, and it is the smaller of the two. As one goes earthward through the F-regions, most of the UV and EUV photons are absorbed by the ionisation in that particular region.

F1 Layer is a sublayer of the F layer

• This layer is located above the E layer and will have the highest density up to 220 kilometres.
• It behaves like the E region, which follows Chapman’s law.
• The critical frequency of this layer spans from 5 MHz to 7 MHz, depending on the application (noon time).
• The density of electrons varies from 2 x 105 to 4.5 x 105.
• The majority of high-frequency waves pass through the F1 layer, with some of them being reflected.
• It has a greater ability to absorb high-frequency waves.
• Its density is lower in the winter than in the summer.

The third region is reached at approximately 150 kilometres (94 miles). This layer is the most interesting for long-distance communications because it contains the most information. Extreme ultraviolet light (EUV) and intense ultraviolet radiation ionise the F-layer, causing it to degrade. 

When exposed to sunlight, it divides the layer into two halves. The bottom section begins at approximately 150 km (94 miles) and is referred to as the “F1-LAYER.” The “F2-LAYER” is the higher section of the atmosphere that begins at around 200 km (125 miles) altitude. The mentioned heights should not be considered absolute; they are subject to ongoing change. 

The F1 layer is significantly weaker than the other layers and has only a minimal role in propagation. It behaves more in the manner of the E-layer than the F2-region. Around midday local time, the F1-layer experiences the greatest amount of ionisation.

The F1 ionisation degree varies in much the same way that the E-layer does, with both being affected by the sun’s elevation in the sky. Except in tropical locations, the F1-layer normally merges with the F2-layer throughout the winter, making it impossible to distinguish one from another. 

This layer’s height fluctuates the greatest, from 160 km (100 miles) to more than 500 km (310 miles) above the surface of the earth, depending on the time of year, the latitudes, the time of day, and, most importantly, the activity of the sun in the sky. Solar eruptions, solar storms, and sunspots contribute significantly to the ionisation density.

Conclusion 

The ionosphere is a dynamic environment that changes constantly. It is, without a doubt, affected by solar radiation. This varies depending on various factors, including the time of day, the geographical location of the planet, and the status of the sun. Radio communications that use the ionosphere as a medium change from one day to the next and even from one hour to the next. Forecasting what radio communications will be possible and how radio signals will propagate is of great interest to a variety of radio communications users, including broadcasters, radio amateurs, and users of two-way radio communications systems, as well as those who use maritime mobile radio communications systems, among many other groups.