The propagation of very short radio waves through the ionosphere and the investigation of ionospheric models
Rohde, Frederick W.
Research noteAbstract: A brief description of the structure and properties of the ionosphere is presented. The refractive index of the ionosphere is discussed in depth for radio waves of 200 MHz and higher. It is shown that the Appleton-Hartree equation when applied to frequencies above 200 MHz can be truncated considerably without paying an appreciable penalty. The refractive index of the ionosphere expressed by the truncated Appleton-Hartree equation depends only on the electron number density and the frequency of the radio wave. The theory of the dual-frequency method for determination of the delay time of radio signals caused by the ionosphere is discussed in detail. It is shown that the ionospheric delay time of a radio signal is directly proportional to the total electron content along the wave path and inversely proportional to the square of the frequency. The accuracy of ionospheric delay time measurements using the SECOR System is examined and found to he about ±10 nanoseconds. A large number of ionospheric data collected by the SECOR System are reported and discussed. The total electron content shows some systematic diurnal variation and variations with latitude and longitude. Some ionospheric models are developed which can he used to describe the general behavior of the measurements. The models are based on the assumption that the electron density is a product of three functions namely, a function of altitude, a function of latitude and a function of longitude. Various cases are simulated using selected model functions.
U.S. Army Engineer Topographic Laboratories.Engineer Research and Development Center (U.S.)
Ionospheric radio wave propagation; Mathematical models; Ionosphere
Research note (U.S. Army Engineer Topographic Laboratories) ; ETL-RN-74-1.
Approved for public release; distribution is unlimited.