On a mechanism forming a broadband maximum in the spectrum of background noise at frequencies 2–6 Hz

Ermakova, E. N.; Kotik, D. S.; Polyakov, S. V.; Shchennikov, A. V.

doi:10.1007/s11141-007-0049-1

Cited by 22 publications

(34 citation statements)

References 10 publications

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“…As is known from [8], this parameter is very sensitive to the ionosphere state at low altitudes up to the F -layer maximum and is completely determined by the sort of the ionospheric-parameter profiles and, consequently, the refractive-index profile of low-frequency waves at these altitudes. Analysis of the spectra of exactly this parameter for a study of the influence of the ionospheric structure of the sub-IAR is also convenient because the parameter , which is the ratio of the magnetic-field components, is free of the frequency dependence of the intensity of low-frequency radiation sources in the ELF range and on the features of the amplitude-frequency characteristic of the magnetic sensors.…”

Section: Results Of Numerical Calculations For Different Ionospheric mentioning

confidence: 99%

“…Numerical calculations show that this parameter depends only weakly on the source direction. It follows from [8] that as the optical depth of the lower ionospheric layers decreases, the broadband spectral maximum in the magnetic-component am- plitudes is strongly shifted towards the frequency of the first Schumann resonance and spreads, becoming hard to record in the experiment. In such cases, it is more convenient to analyze the spectra of the polar- ization parameter.…”

Section: Results Of Numerical Calculations For Different Ionospheric mentioning

confidence: 99%

“…The influence of the sub-IAR [8] on the background ultralow-frequency noise spectra at mid and high latitudes was also analyzed. The polarization spectra (expressed through the amplitude ratio of the right-and left-polarized components of the magnetic field) were numerically calculated for different models.…”

Section: Introductionmentioning

confidence: 99%

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Studying spectral structures in the background ultralow-frequency noise at different latitudes

Ermakova

Polyakov

Kotik

2011

Radiophys Quantum El

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550.383We numerically calculate the horizontal components of the magnetic field in the frequency range 0.1-15 Hz for reception points located at different geographical latitudes. For calculations, we used the solution of the problem on excitation of the Earth -vertically nonuniform anisotropic ionosphere waveguide by a source like a vertical electrical dipole [1]. Calculations were carried out for different numerical and analytical models of the ionospheric parameter profiles [2]. The results of modeling and experimental studies of the spectral resonant structure at the stations on Crete (35.15 N, 25.20 E), New Life (Nizhny Novgorod region, 55.97 N, 45.74 E), Lovozero (68 N, 35 E), and Barentsburg (78.09 N, 14.12 E) were compared. The degree of conformity of the different model profiles to the actual ones was revealed from a comparison of theoretical and experimental spectra. The studies were complemented by an analysis of calculated and experimental spectra of the magnetic noise polarization parameter.

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Section: Results Of Numerical Calculations For Different Ionospheric mentioning

confidence: 99%

Section: Results Of Numerical Calculations For Different Ionospheric mentioning

confidence: 99%

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Studying spectral structures in the background ultralow-frequency noise at different latitudes

Ermakova

Polyakov

Kotik

2011

Radiophys Quantum El

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“…Ermakova et al (2007) associated the eigenmode of this valley with wideband spectral peak around $ 6 Hz, which they named sub-IAR. Here we do not consider this feature.…”

Section: Diurnal Variations Of Ionospheric Parametersmentioning

confidence: 99%

Modeling diurnal variations of the IAR parameters

et al. 2016

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Characteristic feature of the upper ionosphere is the occurrence of the ionospheric Alfvén resonator (IAR) and MHD waveguide, which can trap the electromagnetic waves in the frequency range from fractions of Hz to few Hz. The proposed numerical model is based on the solution of MHD equations in a realistic ionosphere, whose parameters are reconstructed from the IRI model. We estimated, both analytically and numerically, a critical, wave scale dependent, value of the Hall conductance when a wave equation for an uncoupled Alfvénic mode can be used to estimate the spectral parameters of the IAR. The model has enabled us to compare the contributions into the IAR Q-factor of the Joule dissipation in the lower ionosphere and a wave leakage into the magnetosphere. The first mechanism dominates during daytime, whereas the latter mechanism prevails during nighttime. The ground signatures of IAR can be used for monitoring of the F-layer plasma density and vertical total electron content on the basis of relationships derived from the developed IAR model.

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“…In the general case of θ =0 the elements in the expression of upper boundary impedance Z (a 2×2 matrix) depend also on the field angle θ. The theory for the θ =0 case was recently developed by Sobchakov et al (2003) and the numerical code based on their theory and applied to this study is due to Ermakova et al (2007Ermakova et al ( , 2008, and references therein). For the sake of convenience the lengthy expressions of the transversal and longitudinal wave magnetic field components B φ and B r are reproduced in the Appendix together with the adopted assumptions.…”

Section: Theory and Numerical Approachmentioning

confidence: 99%

Magnetic-inclination effects in the spectral resonance structure of the ionospheric Alfvén resonator

et al. 2009

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Abstract. Based on recent developments in the formalism governing the spectral resonance structures (SRS) of the Ionospheric Alfvén resonator (IAR) as observed on the Earth's surface, a numerical code was developed to investigate properties of SRS which can in particular be contributed to magnetic inclination effects. Among the theoretical findings are: 1) SRS is discernible in both orthogonal components, 2) the harmonic structure of SRS is not anymore over frequency equidistantly distributed, 3) the frequency scales of SRS differ in the two normal modes. The theoretically predicted properties could be found in the observations of a low latitude and some of them even in the data of a mid latitude station. The verification, however, is not as straight forward because the predicted effects do not only depend on magnetic inclination but also on the wave angle of the lightning induced electromagnetic wave k-vector with the normal to the magnetic meridian passing through the observation site. So far the formalism is simplified as it deals with a single source situation alone whereas the actual observation is a composite of excitations caused by an average of about 60 flashes of lightning operating all the time, world-wide.

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On a mechanism forming a broadband maximum in the spectrum of background noise at frequencies 2–6 Hz

Cited by 22 publications

References 10 publications

Studying spectral structures in the background ultralow-frequency noise at different latitudes

Studying spectral structures in the background ultralow-frequency noise at different latitudes

Modeling diurnal variations of the IAR parameters

Magnetic-inclination effects in the spectral resonance structure of the ionospheric Alfvén resonator

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