Magnetosphere Definition, Location and Function

To understand more about the Earth's atmosphere and how it functions, we can look at a quick definition of the magnetosphere. The magnetosphere is:

a region surrounding an astronomical object that is formed by the interactions between the Earth's magnetic field and charged particles from solar wind which act as a protective shield.

Such astronomical objects include planets, but are not limited to them. However, they do require an active interior dynamo to be created.

The precise shape of this layer is determined by the intensity of the solar wind and the intensity of Earth's magnetic field. Since these intensities can change, the shape and density of the magnetosphere can change accordingly. Generally speaking, the stronger the solar wind, the more compressed the magnetosphere.

To understand the magnetosphere in greater depth, we will briefly describe the elements involved in its formation below:

• Earth's magnetic field: also called geomagnetic field, this is caused by the combination of planetary rotation and molten iron in the Earth's core together with electrically charged materials within.
  
  
• Solar wind: a stream of charged particles emitted from the upper limit of the solar atmosphere. Specifically, solar wind is made up of electrons, protons and also traces with helium nuclei, among other elements.

To understand how these structures create the magnetosphere, we need to look at its structure. We do this in the section below.

Learn about some of the results of charged particles closer to Earth with our article on the St. Elmo's Fire weather phenomenon.

In terms of the Earth's magnetosphere location, it is in the outermost zone of our atmosphere. This means it occurs after the exosphere, as the magnetosphere is not part of the Earth's atmosphere. We can say that the magnetosphere surrounds our atmosphere, but this is also a simplification.

Part of the problem in understanding the location of the magnetosphere is in its complicated structure. We can have a better idea of where it is positioned by looking at the parts which make up the Earth's magnetosphere:

• Bow shock: a magnetosphere surrounds an astronomical object and its form will depend on this object to some degree. In this case, the astronomical object is our planet Earth. The bow shock is the point at which the charged particles meet the magnetosphere, in this case plasma in the form of solar wind.
  
  
• Magnetopause: this is the abrupt boundary where the pressure from the Earth's magnetic field and the pressure from the solar wind become balanced. The shape and size pf the magnetopause will depend on the amount of pressure being exerted by the plasma, i.e. solar wind.
  
  
• Magnetosheath: in between the bow shock and the magnetopause is the magnetosheath. This is a turbulent space where particles have a high rate of flux. The direction of the magnetic field within this space changes erratically. The reason for this is it is a repercussion from the bow shock, but it protects the Earth from solar wind in doing so.
• Magnetotail: on one side of the Earth's magnetosphere is the above structures which are a result of the confluence of the solar wind and the magnetopause. On the other side is the magnetotail where the Earth's magnetic field and the solar wind pressure becomes balanced and moves away from the planet. It has two lobes, North and South of the planet.

Now we know the constituent parts of the magnetosphere, we cna see that it is difficult to say how far away it is from the earth. This is because different parts of the magnetosphere are at different distances. For example, it is difficult to determine the end of the magnetotail since it trails off the further it leaves earth.

We can say that the bow shock is around 56,000 miles (90,000 kilometres) from the planet. If we take this to be the start of the magnetosphere in relation of the earth to the sun, it can give us an idea of just how close or far away it is. In contrast, the magnetopause is around 60 mi (96 km) from the Earth, with the magnetosheath taking up the space between these points

Earth is not the only planet to have a magnetosphere. Studies estimate that all the planets in our solar system have a magnetosphere, with the exceptions of Mars and Venus. Even one of Jupiter's satellites called Ganymede has a magnetic field, suggesting it could also likely has a magnetosphere.

Now we know the structure and location of the magnetosphere, you may wonder what it is for. While we may not be particularly aware of it, one of the outcomes of our magnetosphere is supporting life on our planet. This is an essential function for us as it protects the planet's surface from the high-energy particles which are found in solar winds. In this way, the magnetosphere is a kind of protective shield which stops the arrival of harmful plasma in the form of solar storm radiation and cosmic rays.

In terms of function, the magnetosphere works by absorbing energy from the solar wind and then releasing this energy via explosions. The release of this energy manifests in geomagnetic storms, substorms and aurora borealis which can be seen in the highest regions of the Earth0s atmosphere, although they are actually above it.

Cracks often arise in the magnetosphere and remain open for a while. When these types of openings occur, it is possible that some energy enters through them, causing problems in the communication satellites and also in the electricity system. There is nothing to worry about in terms of effects on Earth since the cracks usually remain open for only a few hours.

In the previous section we revealed the function of the magnetosphere. With this in mind, you should be able to determine its level of importance. Simply speaking, it is thanks to the magnetosphere that life on Earth is possible. This would otherwise be unviable (or something very different from what it has been and is) as without its presence, the radiation that would reach the Earth's surface would be lethal to the diversity of life that inhabits planet Earth.

In fact, some studies suggest that had the magnetosphere not existed, Earth would have lost most of the water from its atmosphere and oceans. This is because particles from the solar wind would have dissociated water molecules into oxygen and hydrogen atoms. As a result, if the magnetosphere did not exist, the atmosphere would be very different and life forms would not be as we know them.

Learn a little more about solar wind and how it affects our planet earth with our article on why is the sun yellow?

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