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Earth's atmosphere can be separated into four layers as shown in Figure 09-07a and explained in more details in the followings. Figure 09-07b shows the atmospheric layers taken by astronaut on board the International Space Station as the Space Shuttle Endeavour coming in to dock. Several layers of Earth's atmosphere were visible. Directly behind the shuttle is the mesosphere, which appears blue. The white layer is the stratosphere, while the troposphere is in orange color. The ionosphere is transparent except producing auroras occasionally. |
Figure 09-07a Atmosphere | Figure 09-07b Atmospheric Layers |
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The Earth's magnetic field acts as a shield that deflects the solar wind (stream of electrically charged particles) thereby creating an elongated cavity in the wind that is called the magnetosphere as shown in Figure 09-08. The magnetosphere contains large numbers of trapped charged particles, many of which are concentrated in two doughnut-shaped belts called the Van Allen Belts. Disturbances in the solar wind induce batches of charged particles down the field lines into the upper atmosphere around the polar region. These particles interact with atoms and ions to produce auroras as shown in the top right of Figure 09-07a. |
Figure 09-08 Van Allen Belts [view large image] |