Propagation of Extremely Low‐Frequency Radio Waves

Nickolaneko, Alexander P.; Швец, А. В.; Hayakawa, Masashi

doi:10.1002/047134608x.w1257.pub2

Cited by 19 publications

(15 citation statements)

References 34 publications

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“…The propagation constant ν and the normalizing integral N 0 are used in solving the ELF radio propagation problem, and these are derived by using the full wave approach (Galuk et al, 2015;Hynninen & Galuk, 1972;Nickolaenko et al, 2016aNickolaenko et al, , 2016bNickolaenko et al, , 2017 in the regular Earth-ionosphere cavity. Fortunately, there are formulas linking these parameters with quantities used in 2DTE: the complex heights H C and H L .…”

Section: Source Bearingmentioning

confidence: 99%

“…Thus, the algorithm of finding parameters involved in the 2DTE is reduced to the following. First, parameters ν and N 0 are computed by using the procedure described by Hynninen and Galuk (1972), Galuk et al (2015), and Nickolaenko et al (2016aNickolaenko et al ( , 2016bNickolaenko et al ( , 2017. The system of two differential equations is solved numerically for the function δ (ionospheric surface impedance) and its derivative with the parameter λ = ν(ν + 1) being the separation constant of the wave equation in the spherical coordinate system.…”

Section: Source Bearingmentioning

confidence: 99%

“…The propagation parameters of the ELF radio waves were computed for the given day and night profiles of the middle atmosphere conductivity by using the full wave solution in the cavity with the smooth day-night interface. The Riccati equation was used in computations (Galuk et al, 2015(Galuk et al, , 2018Kudintseva et al, 2016;Nickolaenko et al, 2016aNickolaenko et al, , 2016bNickolaenko et al, , 2017. The wave fields were found by solving the 2-D telegraph equation (2DTE).…”

Section: Introductionmentioning

confidence: 99%

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Source Bearing of Extremely Low Frequency (ELF) Waves in the Earth‐Ionosphere Cavity With Day‐Night Nonuniformity

2018

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Impact is modeled of the day-night nonuniformity of the Earth-ionosphere cavity on the source bearing. The smooth day-night interface is considered. The source is located at the 22.5°N; 0°E point, and the observer is positioned at 22.5°S; 0°E. Propagation path position corresponds to 4 hr UT (the night side) and to 8 hr UT (the dayside of morning terminator). We apply the full wave solution to determine the propagation parameters of extremely low frequency radio waves and solve the problem by using the 2-D telegraph equations. The following results were obtained: Terminator impact is absent when the propagation path is at the center of night or day hemisphere. Deviation of source bearing varies with frequency similarly to Schumann resonance pattern and may reach 3-4°at certain frequencies. A weak elliptic polarization is observed for the monochromatic radiation; its sign changes when propagation path shifts from one side of the day-night interface to the other. Temporal variations of the pulsed orthogonal components of horizontal magnetic field form a hodograph outlining complex loops, which obstructs the source bearing. Waveforms change noticeably due to frequency response of a receiver, but the maximum instantaneous deviations do not exceed 1-2°. Effect of the day-night nonuniformity on the Schumann resonance fields does not exceed the level of natural fluctuations caused by the background lightning activity. Therefore, deviations in the source bearing caused by the day-night nonuniformity might be detected exclusively for exceptionally great extremely low frequency transients.Computations were performed in the cavity with a smooth day-night transition (Galuk et al., 2018). The model we use is presented in Figure 1. The upper frame here depicts the height dependence of atmospheric conductivity in ambient day (curve with closed circles) and night (curve with stars) conditions. The ordinate depicts the altitude above the ground level in kilometer, and the abscissa shows the logarithm of air conductivity measures in seimen per meter. The diagram in the lower part of Figure 1 illustrates the geometry of smooth day-night interface.NICKOLAENKO ET AL.10,895

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Section: Source Bearingmentioning

confidence: 99%

Section: Source Bearingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Source Bearing of Extremely Low Frequency (ELF) Waves in the Earth‐Ionosphere Cavity With Day‐Night Nonuniformity

2018

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“…The purpose of this paper is to review the recent activity of seismogenic effects in an old topic of ELF (extremely low frequency) radio waves. For this we have to initially introduce the ELF radio propagation (Nickolaenko et al, 2016). It is possible to regard the Earth‐ionosphere cavity as a waveguide or cavity resonator, and any particular term depends on the frequency or on the electromagnetic wavelength.…”

Section: Introductionmentioning

confidence: 99%

Scattering of Extremely Low Frequency Electromagnetic Waves by a Localized Seismogenic Ionospheric Perturbation: Observation and Interpretation

et al. 2020

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A significant anomaly in the extremely low frequency (ELF) spectra of Schumann resonance (SR) was discovered for the 1999 Chi‐Chi earthquake (EQ) in Taiwan as observed in Japan. Similar phenomena were confirmed for other EQs remote from the observer by a few megameters. An additional effect was detected for nearby EQs. The anomalies were explained by ELF radio wave scattering from a seismogenic disturbance. The global thunderstorms serve as the source positioned at the equator, and the localized seismogenic perturbation was placed above the EQ epicenter. We evaluate a seismic impact on SR power spectra using the realistic conductivity profile of atmosphere. The nonuniformity above EQ epicenter is axially symmetric varying along the radius according to Gaussian law whose scale depends on the magnitude. We use the complex characteristic heights relevant to the regular and disturbed cavities. These are substituted into the two‐dimensional telegraph equation (2DTE) for electric and magnetic fields. Deviations from the regular spectra are the seismogenic modifications that depend on the EQ magnitude. Computations indicate that a distant localized seismogenic nonuniformity provides a noticeable impact when the EQ magnitude exceeds the M = 7 threshold. The effect is also modeled of the nearby (up to 500 km) moderate (magnitude 5.5) EQs. The resonance spectra of disturbed fields become elevated as a whole. The distance dependence of field disturbance repeats seismogenic modifications in the characteristic heights above the observer. Model computations are compared with available observations.

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“…Ohta et al, 2006;Nickolaenko et al, 2006;Hayakawa and Molchanov 2007;Hayakawa et al, 2008aNickolaenko and Hayakawa 2013, 2015a, 2015b. The heuristic knee model was used [Mushtak and Williams, 2002] in most of the papers published on this topic instead of applying a more realistic vertical profile of middle atmosphere conductivity [Nickolaenko et al, 2015[Nickolaenko et al, , 2016a[Nickolaenko et al, , 2016b[Nickolaenko et al, , 2016c[Nickolaenko et al, , 2017[Nickolaenko et al, , 2018Zhou et al, 2016;Kudintseva et al, 2016;Galuk et al, 2017Galuk et al, , 2018aGaluk et al, , 2018b.…”

Section: Introductionmentioning

confidence: 99%

The effect of a compact ionosphere disturbance over the earthquake: A Focus on Schumann resonance

Nickolaenko¹,

Galuk²,

Hayakawa³

2018

IJEAR

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We model perturbations of vertical electric and horizontal magnetic fields of Schumann resonance by a localized seismogenic non-uniformity in the Earth-ionosphere cavity with simultaneous accounting for the day-night non-uniformity. The source and receiver are placed at the same meridian and the latitudes covering 22.5° N and 22.5° S. The propagation path is positioned at the night (60° E) or the dayside (120° E) of morning terminator. The localized nonuniformity moves either along or across the propagation path. The full wave solution is used in the form of Riccati equation for finding the propagation parameters. The spectral components of fields are computed with the 2D (two dimensional) telegraph equations. Numerical estimates were obtained of the impact of the localized ionosphere non-uniformity on the electric and magnetic field amplitudes at a set of Schumann resonance frequencies for various positions of disturbances relative to the propagation path. It is shown that the impact of compact nonuniformity grows with increasing frequency. Field modifications are of interference nature. The day-night asymmetry provides a minor impact, and one may neglect this non-uniformity. The model was applied to interpret observations with a point source in Southeast Asia, Africa, or in South America. The observer was positioned at the Moshiri observatory, Japan. The earthquake focus modifying the conductivity of mesosphere was located at Taiwan. Perturbations of amplitude spectra of Schumann resonance were computed and their similarity to the observations was demonstrated.

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Propagation of Extremely Low‐Frequency Radio Waves

Cited by 19 publications

References 34 publications

Source Bearing of Extremely Low Frequency (ELF) Waves in the Earth‐Ionosphere Cavity With Day‐Night Nonuniformity

Source Bearing of Extremely Low Frequency (ELF) Waves in the Earth‐Ionosphere Cavity With Day‐Night Nonuniformity

Scattering of Extremely Low Frequency Electromagnetic Waves by a Localized Seismogenic Ionospheric Perturbation: Observation and Interpretation

The effect of a compact ionosphere disturbance over the earthquake: A Focus on Schumann resonance

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