Effect of Ionosphere and Inhomogeneity of the Earth Structure on the Polarization Characteristics of Magnetic Field at Frequencies of 0.2–200 Hz in the Near-Field Zone of a Horizontal Grounded Antenna

Effect of the Ionosphere on the Controlled-Source Field in the Frequency Range Between 0.4 and 95 Hz

“…The behavior of the field in the region above 10 Hz on different days is similar, without significant differences. In fact, the field is determined by the structure of the lithosphere and weakly depends on the state of the ionosphere [1].…”

“…Studying the propagation of radio waves in the super low (SLF) and extremely low frequency bands (ELF) (30-300 and 3-30 Hz, respectively, in the International Telecommunication Union designation) in the anisotropic three-dimensional (3D) Earth-ionosphere waveguide is of interest both from the theoretical standpoint and for the practical use in the radiophysical and geophysical applications. In our previous works [1], [2], we considered the influence of the ionosphere on the low-frequency field in the vicinity of the source, i.e., within distances shorter than or comparable to the waveguide height. It was established that the field structure in this region is mainly determined by the conductivity of the lithosphere.…”

“…Below, this approach is used to reveal the reflections from the topside ionosphere in the international experiment FENICS-2019 [10]. In contrast to the previous studies [1], [2], this work is based on the measurement results obtained with a receiver-transmitter distance significantly exceeding 100 km at which the waves propagate in a waveguide mode and the effect of the ionosphere is more pronounced. Due to the rapid attenuation of the low-frequency waves, this distance in a real experiment should not be too large so that the signal-to-noise ratio is sufficiently high and the measurement accuracy allows the detection of the ionospheric effect in question.…”

The Effect of the Ionosphere on the Controlled-Source Field in the Frequency Range between 0.4 and 95 Hz

“…Figure 2a-d The behavior of the field in the region above 10 Hz on different days is similar, without significant differences. In fact, the field is determined by the structure of the lithosphere and weakly depends on the state of the ionosphere [1].…”