4.1.11 Dutton, E.J., Precipitation Variability in the U.S.A, for Microwave Terrestrial System Design, OT Report 77-134 (November 1977). 4.1.12 Initial Assessment - Electromagnetic Compatibility Aspects of the Proposed Microwave System, PNL-2482 (Feb. 1978). 4.2 IONOSPHERIC HEATING AND LAUNCH VEHICLE EFFLUENT EFFECTS 4.2.1 Background Fig. 4.8. Ionospheric Charge Density Distributions The ionosphere can be defined as that region of the earth’s environment in which charged particles — electrons and ions — exist in sufficient abundance to have profound impacts on the chemical and physical mechanisms responsible for the formation and changes in the atmospheric structure. A graphic representation of the ionosphere is given in Fig. 4.8. In deference to historical development, the ionosphere is usually designated according to specific regions, D, E and F; each region being successively higher in altitude and usually greater in electron density. With the advent of the satellite era, the topside ionosphere, or the electron density above the F region, has become of importance, with no definite upper bound for altitude given. All regions of the ionosphere display variations according to diurnal, seasonal, and solar cycle periods. In addition, geophysical disturbances associated ultimately with solar variations give rise to significant changes in the structure of the ionosphere. The ionsophere is at best a dynamic medium varying on time scales from a few seconds to tens of years. Because of the presence of free electrons, the ionosphere causes electromagnetic energy that is sent into it to be refracted and slowed down.
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