The Calculation and measurement of the field strength of high frequency (HF) electromagnetic waves propagating through ionospheric plasma

ABSTRACT PhD Thesis THE CALCULATION AND MEASUREMENT OF THE FIELD STRENGTH OF HIGH FREQUENCY (HF) ELECTROMAGNETIC WAVES PROPAGATING THROUGH IONOSPHERIC PLASMA İbrahim ÜNAL Fırat University Graduate School of Natural and Applied Sciences Department of Physics 2003, Page: 79 The 3-30 MHz waves are called the high frequency (HF) electromagnetic waves. The waves in the high frequency band are reflected by the ionospheric plasma and they propagates to the long distances. Especially, respect to the communications security the HF band is very important sense. For an efficient communication in this band, it is also necessary to know both ionospheric parameters and wave propagation characteristics. In this thesis, analitical expressions of the propagation of the vertical and oblique HF radio waves and the electric field strength of the waves related to the ionospheric parameters have been obtained. Numerical values of the electric field strength have been calculated by using these expressions. The altitudinal, diurnal and seasonal variations of the electric field strength have been investigated. Generally, the attenuation in the electric field strength is higher in daily hours than in night hours. The wave has been mostly attenuated at the low altitudes of the ionosphere. The attenuation of the wave in summer is more than in winter. The attenuation of the wave decreases with increases of the frequency. The obtained theoritical results are compared with the experimental data taken from the ITU-R HF field strength measurement system. Generally, a good agreement between the theoritical and experimental results have been obtained. Keywords: Ionosphere, HF band, field strength, wave attenuation. XII