The upper atmosphere consists of the outermost layers of Earth's atmosphere, above about 90 km altitude, on the edge of space. It is a very different place to the atmosphere we live in at ground level; temperatures reach extremes of cold (< 200 K) and extremes of hot (> 1000 K), waves cause fluctuations with huge amplitudes compared to the ground level weather, and the wind speed is often many times faster than hurricane force. A part of the upper atmosphere is ionised, forming the ionosphere, allowing electric currents to flow and influencing the propagation of radio waves. Photons emitted from the upper atmosphere are observed as the aurora and airglow.
We now know that the atmospheric layers are much more coupled than previously thought, so things happening in the upper atmosphere can influence energy and momentum transfer in the atmosphere below, and vice-versa. Changes in chemical composition in the upper atmosphere caused by energetic particles from the Sun can also lead to important composition changes in the middle atmosphere, for example in the ozone concentration. Meteorologists are therefore expanding their models into the upper atmosphere to improve forecasts of weather and climate. A rapidly increasing number of spacecraft orbit within the upper atmosphere, and therefore an understanding of its variability and dynamics is vital for a society increasingly dependent on space technology.
This module will provide an overview of the physics and chemistry of the upper atmosphere and ionosphere. Methods for measuring and observing the upper atmosphere will also be introduced, and recent research results will be discussed.
Pre-requisites: PHYS1011 AND PHYS1013 AND PHYS1022 AND PHYS2006 AND PHYS3008