What is the Ionosphere?
Earth’s atmosphere varies in density and composition as the altitude increases above the surface. The lowest part of the atmosphere is called the troposphere (the light blue shaded region in the figure to the left) and it extends from the surface up to about 10 km (6 miles). The gases in this region are predominantly molecular Oxygen ( O2) and molecular Nitrogen (N2 ). All weather is confined to this lower region and it contains 90% of the Earth’s atmosphere and 99% of the water vapor. The highest mountains are still within the troposphere and all of our normal day-to-day activities occur here. The high altitude jet stream is found near the tropopause at the the upper end of this region. The atmosphere above 10 km is called the stratosphere. The gas is still dense enough that hot air balloons can ascend to altitudes of 15 – 20 km and Helium balloons to nearly 35 km, but the air thins rapidly and the gas composition changes slightly as the altitude increases.
The ionosphere is a layer of the Earth’s atmosphere that is ionized by solar radiation, also called solar wind. Solar wind exists because the corona, which is the outermost layer of the sun’s atmosphere, is extremely hot and wide. Because it is so wide, a constant stream of hydrogen and helium ions, called solar wind or plasma, is able to leave the sun’s gravity. The solar wind flows away from the sun and toward the Earth, where it affects the Earth’s magnetosphere, ionosphere, and magnetic field. The ionosphere contains plasma and is made up of three layers. The lowest is called the D-region, reaching from 47-59 miles (75-95 km) above the surface of the Earth, and does not contain many ions. The next layer is called the E-region, reaching from 59-93 miles (95-150 km) and containing a slightly higher concentration of ions. The F-region contains the highest density of ions, and reaches from 93-621 miles above the surface.
ANSWER 5. The ionosphere overlaps two of the above four layers. Which two are they? ANSWER 6. At what altitude is the ionosphere generally accepted to begin at? ANSWER 7. Where does the ionosphere end? Explain. ANSWER 8. From the surface up to an altitude of 100 km atmospheric gasses are well mixed. a. What causes this mixing? ANSWER b. What do we call this region? ANSWER 9. There is a layer, which acts as a dividing layer, located between 100 and 120 km. Name this layer. ANSWER 10. While gasses below 100km remain well mixed, from an altitude of 120 km up to the end of our atmosphere the gasses separate out into layers. a. Name the region that extends from 120 km to the end of our atmosphere. ANSWER b. What causes the gasses to separate? ANSWER c. Name the most abundant gas in the bottom-most layer. ANSWER d. Name the most abundant gas in the upper-most layer. ANSWER 11. The ionosphere can be divided into four layers, labeled C, D, E, and F. a. Which of these is closest to the Earths s
). This gas reaches a peak density of a few parts per million at an altitude of about 25 km (16 miles). The ozone layer is shown by the yellow shaded region in the figure to the left. The gas becomes increasingly rarefied at higher altitudes. At heights of 80 km (50 miles), the gas is so thin that free electrons can exist for short periods of time before they are captured by a nearby positive ion. The existence of charged particles at this altitude and above, signals the beginning of the ionosphere a region having the properties of a gas and of a plasma. The ionosphere is indicated by the light green shading in the figure to the left.
