The terrestrial ionosphere

The theory relating to the basic physics governing the behavior of the terrestrial ionosphere is reviewed. The review covers the coupling of the ionosphere to both the neutral atmosphere and magnetosphere, the creation and transport of ionization in the ionosphere, and the ionospheric thermal structure. The review also covers the variation of the ionosphere with altitude, latitude, longitude, universal time, season, solar cycle, and geomagnetic activity. In addition, some unique ionospheric features are discussed, such as the polar ionization hole, the main electron density trough, the ion temperature hot spots, the high-latitude ionization tongue, the equatorial fountain, Appleton's peaks, and the polar wind.