Artificial ionospheric source of low-frequency electromagnetic fields in the problems of environment sounding

Polyakov, S. V.

doi:10.1007/s11141-009-9096-0

Cited by 4 publications

(2 citation statements)

References 12 publications

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“…Ultra low frequency (ULF) electromagnetic waves at frequencies below the 30 Hz naturally and artificially originated were effectively used for investigating the structure of the Earth's crust by sounding (see e.g., Polyakov, 2008; Van Zijl & Jouhert, 1975; Zhamaletdinov et al., 2000, 2012) and for studying phenomena in the near‐Earth space for predicting the “space weather” (e.g., Fedorov et al., 2016; Kotik, 1994; Potapov et al., 2017). There are three types of sources for which it is necessary to be able to calculate the field in the waveguide Earth‐ionosphere.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of ULF Magnetic Fields in the 3D Inhomogeneous Earth‐Ionosphere Waveguide

2022

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We develop an algorithm for calculating the characteristics of the magnetic field of signals in the frequency range of (0.1–20) Hz in the horizontally and vertically inhomogeneous spherical Earth‐ionosphere waveguide. This algorithm involves calculations of the surface impedance of an inhomogeneous ionosphere. The frequency dependences of the amplitude, phase and polarization of the magnetic field generated by a horizontal magnetic dipole were analyzed. It is shown that the horizontal inhomogeneity of the Earth‐ionosphere waveguide can significantly affect the frequency dependence of the amplitude and polarization of the magnetic field, increasing the degree of circular polarization. The horizontal inhomogeneity only slightly influences the results in daytime conditions. The most noticeable difference in the amplitude dependences of the magnetic components and large phase shifts (up to 40°) are observed when the terminator passes through the geodetic line connecting the source and receiver, and in the presence of sporadic layers with a horizontally inhomogeneous structure along the low‐frequency wave propagation path. We compare the calculation results with the magnetic pulsations recorded at Nurmijarvi station during the 2001 campaigns of Kola Peninsula ultra low frequency emitter operation. The obtained results make it possible to qualitatively explain peculiarities of the amplitude and polarization spectra of the artificial magnetic signals recorded in this campaigns that are not explained within the framework of the flat homogeneous waveguide model.

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Section: Introductionmentioning

confidence: 99%

Characteristics of ULF Magnetic Fields in the 3D Inhomogeneous Earth‐Ionosphere Waveguide

2022

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“…It is assumed that the ETL current and the current closing it deep in the Earth's crust form a point magnetic dipole. The approximation of an ionospheric source by a horizontal magnetic dipole is correct in the case h δ i , where h is the height of the air gap in the Earthionosphere waveguide and δ i is the skin depth in the ionosphere [14,15]. The developed calculation technique allows for horizontal ionospheric inhomogeneity, the change in the magnetic field inclination and in the direction to the source along the propagation path of low-frequency waves.…”

Section: Introductionmentioning

confidence: 99%

Features of the Spectra of Ultra-Low-Frequency Magnetic Fields from Horizontal Current Sources: Models of Planar and Spherical Earth–Ionosphere Waveguides

Ermakova

Ryabov

Kotik

2021

Radiophys Quantum El

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We simulate the magnetic field components in the frequency range 0.1-30 Hz from a source such as the horizontal magnetic dipole located in the Earth-ionosphere cavity. Models of uniform spherical and planar waveguides are considered, the advantages of each model are determined, and a comparative analysis of the simulation results is performed. The results of numerical calculations lead to the conclusion about the impact of the IAR (ionospheric Alfvén resonator) and sub-IAR (resonator at altitudes of 80-300 km) on the amplitude spectra of the ultra-low-frequency (ULF) signal. It is also shown that the appearance of strong sporadic layers (with a plasma frequency exceeding 5 MHz at their maxima) along the entire propagation path of ULF fields from the source to the receiver can strongly change the amplitude spectra of artificial signals. A significant increase in the amplitude of the magnetic field at the IAR harmonic frequencies can be observed at night. The sub-IAR effect is responsible for the appearance of a dependence of the amplitude of the magnetic components, which increases with frequency. Phase shifts between the horizontal components of the ULF signal and the spectra of the polarization parameter are also analyzed. It is shown that ionospheric resonators have almost no effect on the phase characteristics of artificial signals in a uniform waveguide approximation, in contrast to the polarization of magnetic ULF fields from a vertical electric dipole. The dependences of the amplitude of the magnetic field of a signal on the distance r to the source and on the direction to the source are also analyzed. It is shown that the dependence of the decay of the magnetic field amplitude with distance can differ significantly from the 1/r 2 law. The radiation pattern is almost isotropic for k 0 r < 1, where k 0 is the wave number in free space. The lines of equal amplitude are stretched along the direction of the current source for k 0 r ≥ 1.

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The Possibility of Experiments on Generating Artificial Ultra-Low-Frequency Radiation in the Ionosphere Using the FENICS Transmitter on the Kola Peninsula

Pilipenko,

Mazur,

Fedorov

et al. 2024

Bull. Russ. Acad. Sci. Phys.

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Artificial ionospheric source of low-frequency electromagnetic fields in the problems of environment sounding

Cited by 4 publications

References 12 publications

Characteristics of ULF Magnetic Fields in the 3D Inhomogeneous Earth‐Ionosphere Waveguide

Characteristics of ULF Magnetic Fields in the 3D Inhomogeneous Earth‐Ionosphere Waveguide

Features of the Spectra of Ultra-Low-Frequency Magnetic Fields from Horizontal Current Sources: Models of Planar and Spherical Earth–Ionosphere Waveguides

The Possibility of Experiments on Generating Artificial Ultra-Low-Frequency Radiation in the Ionosphere Using the FENICS Transmitter on the Kola Peninsula

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