Geoelectric sections of some areas of Palestine and Tanzania were determined based on fund materials of vertical electrical soundings (VES). They are required to verify the predictive maps of the parameters of the geoelectric sections of the Earth's continents. Geoelectric sections obtained on the sea sandy beaches of Palestine washed by the waters of the Mediterranean Sea and on the rock complexes of Tanzania are presented. Using the VES parameters, the frequency dependences of the surface impedance of various types of rocks were calculated in the range from 10 kHz to 30 MHz. Layered geoelectric structures with strongly inductive surface impedance have been established.
A model for the propagation of LF-MF radio waves over ice paths with a spatial change in impedance is proposed and substantiated by numerical calculations. Its features are determined for a two-layer “ice-sea” radio path with a spatial change in ice thickness. The surface impedance, the attenuation function W and the field level |Ez| over a two-layer ice path are considered with a spatial change in ice thickness at a frequency of 300 kHz according to: a) harmonic law and b) sawtooth change in ice thickness. The simulation results are necessary to estimate the conditions for the propagation of LF-MF-HF radio waves along the paths of the Northern Sea Route.
Fund materials of vertical electrical soundings (VES) was used to determine the surface impedance of the layered medium "dry sand - watered sea sand" in the VLF-VHF radio wave. The results of calculations of the frequency dependence of the surface impedance of a three-layers medium "dielectric on watered sea sand" in the frequency range from 10 kHz to 30 MHz indicate that the dielectric layer "dry sand" with thickness up to 2-3 m shifts the phase of impedance to the highly inductive area (from 10 kHz to 10 MHz). The impedance modulus in this frequency range is satisfy boundary conditions of impedance. The phase of impedance reaches –82º. "Dry sand - watered sea sand" medium is an analogue of the "ice-sea" medium with a strong inductive impedance in the VLF-HF ranges. There are wide distribution of sand beaches on all oceans and seas of the Earth. "Dry sand - watered sea sand" structures are typical for large areas of the Earth and calculations of coastal refraction of the "land-sea" in radio systems it should take into account. The modeling results are required to check the forecast maps of geoelectric sections (GES) of the Earth's continents and for calculations of radio waves propagation.
The features of the frequency dependence of normalized surface impedance for the “ice-sea” structure at frequency of 300 kHz are determined. Five models of ice structure were considered, which take into account the change in ice thickness based on the spatial Fourier series. In the calculations, the ice thickness varied from 0.2 to 3.8 m. The results of modeling are necessary to assess the conditions for LW-MW radio waves propagation along the paths of the Northern Sea Path.
Electrometric studies of the aquatic environment of Lake Baikal, the Selenga river, and other rivers, lakes, and wells located in different areas of the natural Baikal territory were performed. The electrical resistivity of salt lakes in the region and the seas were compared. Samples of drinking tap water from Irkutsk, Yakutsk, and Ulan-Ude and wells of the villages of Baikal region were measured. Significant variability of resistivity at various points of water sampling due to its different salinity were established.
For calculations of the electromagnetic field over the two-layer structure “thick ice-sea”, the areas of applicability of the impedance boundary conditions for a vertically polarized wave in the range of 0.01 ˗ 120 MHz are determined. Seven models of ice cover are considered. The ice thickness varied from 2 to 9 m. Results are needed to calculate the attenuation function W and the field level in the LF-MF-HF range of radio waves.
Propagation conditions of radio waves over the “ice-sea” structure with a highly inductive impedance are often more favorable than over a clear sea due to the appearance of a surface electromagnetic wave. Numerical calculation algorithms for various radio wave propagation path models have been developed. The method of making prognostic maps of the surface impedance of the “ice-sea” structure according to the ice situation maps for the Arctic Ocean (AO) in different seasons of the year is considered. A formula is proposed for converting the spatial dependence of the ice thickness into the spatial dependence of the surface impedance at a fixed frequency in VLF-LF-MF ranges. Calculations of surface impedance for various types of sea ice are presented.
For calculations of the electromagnetic field of the two-layer "thin ice-sea" structure, the areas of applicability of the impedance boundary conditions are determined depending on the thickness of the ice and the angle of incidence of the vertically polarized wave. Results are needed to calculate the attenuation function W and the radio wave field level. It is shown that for the "thin ice-sea" structure, taking into account the dependence of surface impedance on the angle of incidence is important for over-the-horizon radar systems in the HF range of radio waves. In the VHF range for ice 80 cm thick, frequency bands are identified in which impedance boundary conditions are applicable.
Results of the modeling of the propagation of LF-MF radio waves over radio path with variable surface impedance were considered. Formulas to convert the spatial dependence of ice thickness in the spatial dependence of the surface impedance at a fixed frequency of LF-MF ranges were offered. The calculation of the field magnitude was carried out using the program of calculation of field of an attenuation function W by the method of the Hufford’s integral equation. Results of calculations of surface impedance, an attenuation function and field magnitude on a frequency of 518 kHz on a 400 kilometers section of the radio path “Tiksi - North pole”.
The report is devoted to the foundation of the method of calculation of the service zone of the MF radio beacon for transmission of differential corrections of the global navigation satellite system (GNSS) over high-latitude manysectional impedance paths in summer and winter time. Methods of calculation of the Earth’s wave field over inhomogeneous radio paths including over layered “ice-sea” structure are considered. On a base of the analysis of propagation conditions of radio waves, a new method of calculation of the service zone of the radio lines in the Arctic basin was submitted. Numerical algorithms for various models of the propagation of radio waves were developed and tested. The method consists in using the proposed set of algorithms, maps of geoelectric sections (GES) of underlying layered medium, digital relief maps, vegetation and ice cover for the calculations of Earth’s wave fields.
The paper is devoted to estimation of the LF-MF high latitude communication radio lines range on surface electromagnetic waves (SEW). A surface impedance of sea areas of water in summer and winter time is considered. An example of calculations of the ground wave field over inhomogeneous impedance paths including stratified inhomogeneous structure “ice-sea” is given. It is shown that due to the emergence of SEW the Arctic radio lines range increases significantly.
Predictive map of geoelectric sections of the North China on a scale of 1 : 2 500 000, necessary for calculation of propagation of VLF-MF radiowaves, is constructed. Taking into account the layered structure of the underlying medium, this map is capable of increasing the accuracy of electromagnetic field calculations by 1.5-3 times as compared to the Morgan-Maxwell map. The methodology of the geoelectric mapping is described. The studies of electrical properties of layered media by combined radio and geophysical methods in a variety of natural and geological conditions, and the proposed method of geoelectric mapping have resulted in the construction of a new generation of maps showing the electrical properties of the underlying medium that account for the layered structure of the crust and have no analogues in the world.
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