The space above earth is important for a lot of reasons. The climate change and ozone layer depletion are not something that is entirely new. Ozone (O<sub>3</sub>)  layer which is the layer up in the Earth's atmosphere (stratosphere) which helps minimise the effects of the incoming ultraviolet (UV) radiation.
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<sub> Two giant swaths of radiation, known as the Van Allen Belts, surrounding Earth were discovered in 1958 by NASA Goddard Space Flight Center(License: CC BY 2.0]: <a href="https://www.flickr.com/photos/gsfc/8517114274"> 
Flickr </a></sub> </center> 
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The UVB radiation is one of the increases the risk of cancer of the skin, cataracts, sunburn, and other adverse effects on the environment which affects plants, animals and different life on Earth. The cause of the depletion of the ozone-rich layer, which acts as a shield, is a result of man's activities through the use of some specific materials.

Such materials include refrigerants and aerosols that contain chlorofluorocarbons (CFCs), and halons-these are gases which breaks down (through reduction) ozone molecules which decrease its UV-absorbing capacity.

Other ozone depleting practices include the carbon dioxide emission into the atmosphere from fossil fuel, bush burning etc.

But do all human activities [damage the Earth's shield](https://www.epa.gov/ozone-layer-protection/basic-ozone-layer-science) as ozone layer depletion has shown? Let's find out.



Back in 30th August 2012, NASA launched two robotic spacecraft, [Van Allen Probes](https://en.wikipedia.org/wiki/Van_Allen_Probes), into space. Its mission is to explore the Earth's radiation.

They have been orbiting the Earth at speeds of up to 3200km/h (2,000mph) on the [Van Allen radiation belt](https://en.wikipedia.org/wiki/Van_Allen_radiation_belt). It is the area of the Earth's magnetic field which surrounds the charged particles.

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<center> <img src="https://steemitimages.com/DQmdUG8BnMqzS73F6gGZRAgrJmTWuL7RCYXNhaAkt6Xr1Xk/image.png">
<sub>  The Earth showing the Van Allen radiation belt (License: Public Domain]: <a href="https://commons.wikimedia.org/wiki/File:Van_Allen_radiation_belt.svg"> 
Wikipedia Commons </a></sub> </center> 
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The inner belts begin from altitudes of between 640 to 9,600km while the other belt occurs at altitudes of about 13,500km to 58,000 km.

The two spacecraft follow the same path while measuring the changes in the magnetic and electric field properties of the Van Allen belt to give scientists insight to study and understand the changes that occur in both space and time.


Sometime in 2017, the probes made an interesting discovery. It discovered that an unusual behaviour of the charged particles which is enveloped by the Earth's magnetic and electric field.

The Van Allen belt is merely an area in the atmosphere where the solar charged radiation made up of high energy protons and electrons from the Sun somewhat gets "trapped" or stopped by the Earth's magnetic effect.

It is not a stationary wall or fence, it shrinks and expands. 

The discovery that the probes made was to pinpoint the role very low frequency (VLF) signals plays in determining the formation of the radiation belts.

Just as the name implies, a VLF is radio frequency that is very low and usually on the scale of 3 to 30 kilohertz (kHz) that is employed in military communication and submarines. The reason is simple; the VLF signals are capable of penetrating 40 meters (120 feet) of saltwater and can travel great distances on the ground. VLF propagation distance lies between the range of 5000 to 20,000km <sup>[1](https://books.google.com.ng/books?id=IQWHj2bgcxcC&pg=PA419&redir_esc=y#v=onepage&q&f=false)</sup>.


The long-distance propagation of VLF signals uses the Earth-ionosphere propagation mechanism. In this transmission, the earth's upper surface, about 60km (37 miles) to 90 km( 56 miles) called the D-layer reflects the signals as it strikes it towards the earth which does the same. Thus the earth and ionosphere form a channel for its propagation.

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<center> <img src="https://steemitimages.com/DQmdddRrQVpZ7csvrzGRkek3fJJseq9hUi9urTvhxDYrvXt/image.png">
<sub>  VLF's Signal Earth–ionosphere Waveguide (License: CC-SA-3.0]: <a href="https://en.wikipedia.org/wiki/File:Groundandskywave.jpg"> 
Wikipedia Commons </a></sub> </center> 
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The scientists after the analysis the Van Allen probe's data believe the solar radiation protective bubbles was as a result of the very low-frequency signals from earth's radio communication which includes submarine communication have contributed to the location and how the belts move.


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#### Conclusion

<br>


Five months ago I wrote about [solar storm](https://steemit.com/science/@greenrun/how-a-massive-solar-storm-could-obliterate-technology-but-an-earth-umbrella-might-be-the-ultimate-solution) which is a real [danger](https://www.popsci.com/science/article/2011-05/are-we-prepared-catastrophic-solar-storm) as shown by the Carrington Event of 1859 in which a solar storm disrupted radio services and even shocked telegraph line operators.

More recently on 9 March 1989, a [coronal mass ejection](https://en.wikipedia.org/wiki/Coronal_mass_ejection), another name for a solar storm where electromagnetic radiation from Sun gets ejected into space, [hits Quebec in Canada disrupting power](https://en.wikipedia.org/wiki/March_1989_geomagnetic_storm) and shortwave radio interference.


Even though this was purely by accident as man never really plan for their VLF's radio communication on Earth to do any particular change in space, it is a welcome one.



<sup>**References**</sup>

* <sup>[Basic Ozone Layer Science](https://www.epa.gov/ozone-layer-protection/basic-ozone-layer-science)</sup>
* <sup>[NASA's Van Allen Probes Spot Man-Made Barrier Shrouding Earth](https://www.nasa.gov/feature/goddard/2017/nasas-van-allen-probes-spot-man-made-barrier-shrouding-earth)</sup>
* <sup>[An impenetrable barrier to ultrarelativistic electrons in the Van Allen radiation belts](https://www.nature.com/articles/nature13956)</sup>
* <sup>[We may have accidentally formed a protective bubble around Earth](https://www.popsci.com/radio-wave-shield-space-weather)</sup>


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