Since 1958 scientists have been making discoveries about the Earth's near space environment. Through these studies they have come to the conclusion that the near space environment is not empty as previously thought, but actually is filled with magnetic fields, electric fields, matter, energy, and activity. The main regions of space are the ionosphere, magnetosphere,plasmasphere, and the radiation belts.
The Ionosphere
The ionosphere is the ionized region of the atmoshpere made primarily of plasma. It was created by the ionizing action of the sun's radiation on the Earth's upper atmosphere. It only makes up about 0.1% of the Earth's atmosphere, but it is still a very important region.
The ionosphere is protected from the direct solar winds by the magnetosphere, but it is still the primary shield that absorbs the majority of energetic wavelengths in the atmosphere. The ionosphere has positive and negative effects on wavelength signals. Longer wavelength signals can actually "bounce" off of the ionosphere allowing them to travel farther distances, but since the ionosphere is not smooth a shorter wavelength signal can be scatter when it hits the ionosphere causing a loss of signal strength.
Scientists can explore and monitor the ionosphere several ways. The most common way for them to predict the state of the ionosphere is by monitoring the sunspots. This works because sunspots increase the solar winds and the interaction between the solar winds and the ionosphere increases the energy in the Earth's magnetic field which can then be detected. Scientist also explore the structure of the ionosphere by "bouncing" radiowaves of different frequencies off of it and determining the differences between the reflected waves and the ones they transmitted. Another way scientists examine the ionosphere is by looking at the changes made to radiowaves transmitted from satelites and stars throught the ionosphere.
The Magnetosphere
The magnetosphere is the region of the atmosphere directly above the ionosphere. It is controlled by the Earth's magnetic field which extends thousands of miles into space. The magnetosphere shields Earth from the direct solar winds and is structured in large, cell-like regions.
The first region of the magnetosphere is the bow shock region. This is the region where the solar wind first encounters the magnetosphere. When this happens the solar wind abruptly changes direction, forming the bow shock region. Attempted passage through this region greatly reduces the speed and changes the direction of the particles. The now shocked solar wind particles deflect around the magnetosphere through the magnetosheath.
The magnetotail is another main region of the magnetosphere where solar wind plasma is found. In contrast to the magnetosphere which is compressed by the solar wind, the magnetotail is stretched and elongaged by the solar wind. Many large changes can take place here and ions and electrons are often engergized. It is also the main sourse of the polar aurora. Inside the magnetotail there is a plasma sheet which is a hot region of different thickness and density. This plasma sheet it divided by a thin neutral sheet. This sheet is located where the northern and southern magnetic fields meet and cancel eachother out, so it is considered magnetically neutral. Inside of this plasma sheet the upper half of the plasma is directed upward, toward the Earth, and the lower half is directed downward, away from the Earth. Adjacent to this plasma sheet is the northern and southern tail lobes. This area has hardly any plasma and is separated from the plasma sheet by a very thin plasma sheet boundary layer.
Scientists are now starting to compare our magnetosphere to that of other planets. In doing this they realized that the magnetosphere of other planets is bullet-shaped just like ours. They also discovered that the giant planets have much larger magnetospheres than Earth's. Since this is an on going field of study I think there will be many more discoveries in this area in the near future.
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