ThermosphereIn the thermosphere, the absorption of solar z- and ultraviolet radiation results in high temperatures (1000°C or more) and considerable ionization. The various layers of the ionosphere are found here. It must be kept in mind that the high temperatures of the thermosphere represent the average molecular energies there; because the number of molecules per m3 is also small despite the high temperature.


History of the Thermosphere

We have a long history of accurate measurements of atomic density at a variety of altitudes in the thermosphere. This data is derived from measuring the drag on various spacecraft and satellites, and that gives us over four decades of detailed measurements. EUV photons have been directly measured only since the launch of the TIMED/SEE instrument in 2002, so a proxy for EUV irradiance must be used. The only reliable proxy that has been around for long enough is the continuous observation of the 10.7 cm solar radio flux. While it is not a perfect indicator, it is stable and well calibrated.

Application of the Thermosphere

The Space Shuttles orbits in a region well above the lower thermosphere, and upon reentry, it passes through it, however only briefly. A promising alternative approach is to tether a probe from a larger orbiting platform, and then lower the probe into the region of the thermosphere. The feasibility of this technique has already been demonstrated by NASA's SEDS experiments.



  1. Beiser, A. (1988). Physical Science (2nd Edition). New York, NY: McGraw Hill
  3. Johnson, R.M. (1995). The upper mesosphere and lower thermosphere: a review of experiment and theory. Washinton, D.C.: American Geophysical Union

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