Schumann Resonance Parameters Research Articles

Seasonal and Interannual Variations in the Schumann Resonance Observed in the ELF Electromagnetic Networks in China

AbstractBased on 9 years of quasi‐continuous data observed at extremely low‐frequency electromagnetic stations, the long‐term variations of Schumann resonances (SRs) are compared and analyzed. We obtained two major parameters, namely the peak intensity and peak frequencies by Lorentz fitting and focus on their seasonal and interannual variations of the first three modes in 10 stations. Fengning station was taken as an example to show the seasonal variations of the intensity and frequency of each electromagnetic component and each mode of SR, with the intensity reaching the maximum in Northern Hemisphere summer and minimum in winter; while the frequency has an inverse phase. And the amount they change from summer to winter also shows different characteristics. The interannual variation of the 10 stations shows the unified law of change in the magnetic field than in the electric field. Finally, in conjunction with observations from other regions of the globe, the periodic intensity variation and migration of the lighting activities were considered the dominant controlling factors for the SR parameters. And by comparing with the El Niño index and solar X‐radiation flux, the strong links between SR parameters and the 11‐year solar cycle are confirmed, and intensity enhanced under the influence the 2015/2016 super E1 Niño phenomenon.

Investigation of the Reaction of Schumann Resonances to Short Transient Geophysical Events Under the Influence of Atmospheric Electromagnetic Noise

AbstractThe interference of electromagnetic signals from lightning discharges in the frequency range below 100 Hz is the source of a global electromagnetic phenomenon in the Earth's atmosphere known as the Schumann resonance (SR). Changes in the parameters of SR signals caused by geophysical disturbances make it possible to study the state and dynamics of the lower ionosphere. When calculating the SR parameters, there are problems associated with the impact of electromagnetic interference of natural and anthropogenic origin. The main natural sources of interference are signals associated with the radiation of nearby lightning discharges, as well as the influence of the Alfvén ionospheric resonator. The paper presents a new method for calculating the SR parameters, which makes it possible to find the spectra distorted by interference, mention above, and exclude them from further processing. The developed technique significantly increased the temporal resolution of the obtained data on the frequency and amplitude of the SR. Due to this, it became possible to study the influence of fast heliogeophysical disturbances (such as solar X‐ray flares) on the lower ionosphere and, as a consequence, on the parameters of the SR. An analysis of the experimental data made it possible to establish a linear dependence of the SR frequency on the logarithm of the X‐ray flux in the range up to 0.2 nm during a class X solar flare.

Schumann resonance data processing programs and four-year measurements from Sierra Nevada ELF station

In this work, we present to the scientific community the measurements taken during four years, from March 2013 to February 2017 inclusive, by the Extremely Low Frequency Sierra Nevada station, Spain, together with the data processing programs developed in Python (version 3.8) to extract the Schumann resonance (SR) parameters (i.e., amplitudes, resonant frequencies, resonance widths) in 10 min time periods from these records. The measurements correspond to the voltage induced by the atmospheric electromagnetic field at the north-south and east-west oriented magnetometers of the station. The process comprises four stages. The spectrum, calibrated in the frequency band ranging from 6 Hz to 25 Hz, is obtained at the first stage using the Welch method with Hann windows. The second step eliminates the anthropogenic noise generated by different undesired sources. Next, a non-linear fit of the measured spectrum combining Lorentzian functions together with a linear term is carried out in order to identify the presence of SRs and quantitatively characterize them. This third step is carried out using the Python package Lmfit, which implements the Levenberg-Marquad algorithm. Finally, a compact and easy-to-read output is generated at the fourth stage, using the power of the Numpy arrays and the npz format. In addition, four Jupyter notebooks with the description of the code and the possibility of their use in interactive mode are presented as supplementary material with this paper.

Correlation of local lightning activity with extra low frequency detector for Schumann Resonance measurements

A dedicated extremely low frequency (ELF) detector has been constructed and used successfully for Schumann Resonance (SRs) measurements in N.W. Greece. The main objective of this work was to investigate the effect of local lightning activity on the signal of our ELF detector and consequently on the estimated SRs parameters, namely the power, the frequency and the quality factor of each mode. Therefore, several measurements were taken into account for the ELF signal continuously recorded and the lightning intensity in a specific range around the ELF detector. Additionally, a simple filtering technique was used, in order to reject the distorted SRs spectra. The statistical analysis performed showed a positive and statistically significant correlation between the lightning events and the recorded magnetic component of the ELF signal. It was found that local lightnings have a significant impact on the SRs measurements, and it is necessary to be removed from the background signal.

Asteroid impact, Schumann resonances and the end of dinosaurs

It is believed that an asteroid/comet impact 65 million years ago ended the dinosaur era. The researchers named the corresponding impact crater Chicxulub, the Mayan word roughly translated as “the dragon's tail.” We estimate the expected magnitudes of the Schumann resonance fields immediately after the Chicxulub impact and show that they exceed their present-day values by about 5×104 times. Long-term distortion of the Schumann resonance parameters is also expected due to the environmental impact of the Chicxulub event. If Schumann resonances play a regulatory biological role, as some studies indicate, it is possible that the excitation and distortion of Schumann resonances after the asteroid/comet impact was a possible stress factor, which, among other stress factors associated with the impact, contributed to the demise of dinosaurs.

Study of the variations in the Schumann resonances parameters measured in a southern Mediterranean environment.

Schumann resonances (SRs) provide a unique tool for exploring continuous and long-term monitoring of global environmental parameters, although their detection and study is a very complex task. This paper presents diurnal and seasonal variations of principal parameters, namely the resonance frequency, the Q-factor, and the power of SRs, in the North-South (NS) magnetic field component for the first five modes from Extra Low Frequency (ELF) measurements. These were acquired at the observation site located at Doliana, Kalpaki, in the Region of Epirus, North West Greece. These variations are the first ones reported for the principal parameters in the South Eastern Mediterranean area and correspond to the one-year measurement period from 2016 to 2017. The comparison with variations at several observations sites is also discussed. Moreover, correlation with global lighting centers, as well as local lightning activity, and SRs parameters variation is attempted.

On the Need of a Unified Methodology for Processing Schumann Resonance Measurements

AbstractThe monitoring of natural electromagnetic activity in the extremely low frequency range is considered as a means of obtaining global information on the lightning activity and other parameters concerning the state of the Earth's atmosphere. In this sense, the possible application of the study of Schumann resonances (SRs) to environmental monitoring systems has already been proposed in the recent past. However, the usual lack of details existing in the literature concerning the process of extracting SR parameters hinders the development of global networks intended for environmental purposes. In this paper, the methodology used to extract SR information from data measured at the Sierra Nevada extremely low frequency station, Spain, is described in detail. The process is split in three main parts: the determination of the amplitude spectrum from the low‐amplitude noisy signal measured, the anthropogenic noise elimination and, finally, the calculation of an analytical function to fit the filtered amplitude spectrum from which SR parameters can be precisely defined. Some different options in the method are considered, and their effect on the SR results has been quantified. Significant differences in the final results have been observed in some of the options considered. As a conclusion of this work, it becomes clear that, if data from different research groups are to be shared and quantitatively compared, a standardization of the process is required or, at least, some details on the station and this process should be provided together with the SR results.

Schumann resonance parameters at Kuju station during solar flares

We examined the Schumann resonance (SR) at low-latitude station KUJ by comparing with solar X-ray flux and solar proton flux at a geostationary orbit. For intense solar activity in October-November 2003, the reaction of the SR frequency to X-ray enhancement and SPEs was different. The SR frequency in H component increased at the time of the Xray enhancement. The response of SR seems to be caused by the increase of the electron density in the ionospheric D region which ionized by the enhanced solar X-ray flux. In the case of the SPEs, the SR frequency in D component decreased with enhancement of solar proton flux. We suggest that the SPEs caused the decrease of altitude on the ionopheric D region at high-latitude region, and the SR frequency decreased.

3-D Modeling of Electromagnetic Wave Propagation in the Uniform Earth-Ionosphere Cavity Using a Commercial FDTD Software Package

Extremely low frequency (3–3000 Hz) electromagnetic (EM) wave propagation in the (3-D) cavity composed of the earth’s crust and uniform ionospheric lossy layers is modeled using the finite-difference time-domain algorithm set in a commercial simulation software. EM propagation and attenuation in the Earth-ionosphere waveguide are computed, and the Schumann resonance (SR) parameters are obtained from the spectra. The overall accuracy of the SR parameters surpasses 90%, despite a fairly coarse resolution of the system. We show that a commercial software can accurately and efficiently model such a large and complex geophysical system.

Characteristics of Schumann Resonance Parameters at Kuju Station

The ground magnetic field variation in the extremely low frequency (ELF) range has been measured by an induction magnetometer at Kuju, Japan (KUJ; M.Lat. = 23.4 degrees, M. Lon. = 201.0 degrees) since 2003. The first mode of the Schumann resonance (SR) around 8 Hz can be seen at KUJ. The SR in H (horizontal northward component) shows maximum peaks around 08 UT and 15 UT. In the case of D (horizontal eastward component), the SR shows its maximum peak around 08 UT. These peaks are coincident with the enhancement of lightning activity in Africa and Asia. Thus, we found the influence of the lightning activity on the observed SR at KUJ.

Schumann Resonances Observed at Maitri, Antarctica:Diurnal Variation and its Interpretation in Terms of Global Thunderstorm Activity

Schumann resonances (SRs) are the AC components of the global electric circuit and are excited by the lightning activity within the Earth-ionosphere waveguide. An induction magnetometer, which was operated from the Indian Antarctic station, Maitri (70.8°S, 11.7°E), served to examine the SR parameters, namely the amplitude and frequency, in the north-south (H NS ) and east-west (H EW ) magnetic components. The analysis for the first resonant mode presented in this work reveals a strong UT variation in its amplitude in seasonal as well as yearly timescales. The NS amplitude reveals a semi-diurnal variation with peaks at ~1000 and ~2100 UT, whereas the EW amplitude exhibits a strong diurnal variation with a pronounced peak at 1600 UT. The diurnal curves for the frequency for both components are similar in nature to those for the amplitude, but for a time shift. The diurnal trend in the amplitude is retained irrespective of seasons, whereas significant difference are noticed in the frequency behaviour between the summer and winter seasons, especially in the EW component. The observed diurnal variation in the SR intensity is explained in terms of the dominant thunderstorm activity centred over the three convectively active regions: Asia/Maritime Continent (Indonesia), South America and Africa. The diurnal variation in frequency depends not only on the location of the thunderstorm region with respect to the observer, but also on the ionospheric day/night conditions and the Earth-ionosphere cavity thickness.

Variability of Schumann resonance parameters observed at low latitude stations in China

This paper presents a comprehensive analysis of the Schumann resonance (SR) parameters observed at low latitude stations in China for the first time. Variations of SR peak frequency and intensity on different timescales (from minutes to years) are analyzed in detail. Diurnal and seasonal variations are shown and the source-observer distance is calculated to confirm the contributions of lightning activity. Differences in the profiles of SR intensity between the NS and EW components are due to the effects of the source-observer distance and the relative position of the observer to the sources. Diurnal frequency variations are more complicated and cannot be directly linked with the three thunderstorm centers. Seasonal variations are clear for intensity but not for frequency. The differences in the diurnal and seasonal variations between the SR intensity and frequency show that the greatest contributor to SR intensity is global lightning activity, while the SR frequency is not affected solely by lightning, as certain other factors involving ionosphere properties may play non-negligible roles. We also emphasize that our observations do not show a distinct day–night change in the SR parameters, and that the SR intensity does not show abrupt changes across terminators. This observation is consistent with previous simulations. Finally, the response of the SR to a solar flare is discussed. The flare leads to a sudden increase of about 0.2Hz relative to the 2σ level of the SR frequencies in the first three modes, which is in agreement with other works in the literature. This frequency enhancement is explained using theoretical calculations.

Analytical modeling of Schumann resonance and ELF propagation parameters on Mars with a multi-layered ground

Two electrically conductive planetary spheres, the ionosphere and the ground, form a spherical waveguide. Within such a planetary cavity a phenomenon called Schumann resonance (SR) can occur. It is a resonance of extremely low frequency (ELF) electromagnetic waves. The resonance parameters are strongly related to the electromagnetic properties of the cavity. On Mars, as there is no liquid water at the planetary surface, the ground has a low conductivity. In such a situation, ELF waves penetrate into the planetary subsurface up to many kilometers depth. To examine the influence of low-conductivity grounds on ELF propagation, we have introduced a recently developed analytical method, which enables to estimate the propagation parameters and explicate their dependence of the ground properties. Since the presented model is fully analytical, it is computationally efficient and can be very useful in finding inverse solutions. To demonstrate the potential of the method, we present the relationship between individual ground properties and the parameters of Schumann resonance. The obtained results indicate that Martian exploration performed by one ELF station located at the planetary surface can reveal, along with the properties of the ionosphere, the existence of liquid water under the Martian surface.

116 THE EFFECT OF LENALIDOMIDE ON HEALTH-RELATED QUALITY OF LIFE (HRQOL) IN PATIENTS WITH MDS: RESULTS FROM THE MDS-005 TRIAL

This paper presents a comprehensive analysis of the Schumann resonance (SR) parameters observed at low latitude stations in China for the first time. Variations of SR peak frequency and intensity on different timescales (from minutes to years) are analyzed in detail. Diurnal and seasonal variations are shown and the source-observer distance is calculated to confirm the contributions of lightning activity. Differences in the profiles of SR intensity between the NS and EW components are due to the effects of the source-observer distance and the relative position of the observer to the sources. Diurnal frequency variations are more complicated and cannot be directly linked with the three thunderstorm centers. Seasonal variations are clear for intensity but not for frequency. The differences in the diurnal and seasonal variations between the SR intensity and frequency show that the greatest contributor to SR intensity is global lightning activity, while the SR frequency is not affected solely by lightning, as certain other factors involving ionosphere properties may play non-negligible roles. We also emphasize that our observations do not show a distinct day–night change in the SR parameters, and that the SR intensity does not show abrupt changes across terminators. This observation is consistent with previous simulations. Finally, the response of the SR to a solar flare is discussed. The flare leads to a sudden increase of about 0.2 Hz relative to the 2σ level of the SR frequencies in the first three modes, which is in agreement with other works in the literature. This frequency enhancement is explained using theoretical calculations.

Diurnal and seasonal variations in the Schumann resonance parameters observed at Chinese observatories

The Schumann resonances (SRs) are of great significance for probing the global circuit. The diurnal and seasonal variations in mode amplitudes and frequencies of the first four modes of SR magnetic components based on 2 years measurements at the stations located in China are firstly presented here. The frequencies of all the four modes have their maxima during boreal winter and minima during summer, while the mode amplitudes change oppositely. The variations of both frequencies and amplitudes show their strong relationships with the lighting activity in south-east Asia (0800 UT) which is the nearest source to the observatories in China, while the other sources in Africa (1400 UT) and South America (2000 UT) have less effects on the mode amplitudes of both magnetic components. The effect of day–night asymmetry on SR parameters is estimated by a 3D-FDTD model of the Earth–ionosphere cavity with a single pulse traveling around the equator in a day. Two models of the Earth–ionosphere cavity, namely, a symmetric cavity and a cavity with day–night asymmetric conductivity profile are exploited. It is clear that the minima in the diurnal patterns of the mode frequencies near local sunrise/sunset times are mainly related to the migrations of the global lighting activity, not the day–night ionosphere asymmetry. Moreover, it is concluded that the ionosphere-induced variations of SR parameters including mode frequencies and amplitudes are much smaller than the variations resulting from lighting activity.

Seasonal and diurnal regularities of the Schumann resonance parameters in different regions of the earth

A comparison of the temporal regularities of the Schumann resonance parameters registered at different observation points (in Hollister, Negev, and Lekhta) with the results of electromagnetic background monitoring in Tomsk is performed. It is demonstrated that the frequencies have similar dynamics at different points at the same time, whereas the similarity of amplitudes is observed only at local time.

Numerical analysis of ionosphere disturbances and Schumann mode splitting in the Earth‐ionosphere cavity

The variability of ionosphere properties plays an important role in the Schumann resonances (SR), amplitudes, frequencies, and Q factor. Therefore, as atmosphere ionization is related to solar activity, SR could be devised as a source of indirect parameters that locally from the surface of the Earth could provide space weather information. A proper understanding of this link to SR parameters can be obtained through finite difference time domain (FDTD) simulations, specifically with the numerically obtained modes and frequencies that relate frequency shifts to the day‐night asymmetry and polar inhomogeneities. Day‐Night asymmetry is observed to have a minor influence in SR; however, large changes are deduced from polar nonuniformities associated to Solar Proton Events (SPE) and X‐ray bursts. The field volume distribution of the modes provides the understanding of the SR variability, related to the altitude and latitude of the ionization phenomenon.

Diurnal and seasonal variations in the Schumann resonance parameters at Moshiri, Japan

Diurnal and seasonal variations in the Schumann resonance parameters at Moshiri, Japan

A case study on the ELF characterization of the Earth–ionosphere cavity: Forecasting the Schumann resonance intensities

Schumann Resonances (SR) are the electromagnetic (EM) phenomena which occur in the cavity formed by the conducting Earth and the ionosphere, with peak mode frequencies close to 8, 14, 20, 26, 32 Hz, etc. [Price, C., Melnikov, A., 2004. Diurnal, seasonal and inter-annual variations in the Schumann resonance parameters. Journal of Atmospheric and Solar-Terrestrial Physics 66, 1179–1185]. The spectral characteristics of the SR modes are defined by their resonant mode amplitudes, center frequencies and half-widths [Price, C., Melnikov, A., 2004. Diurnal, seasonal and inter-annual variations in the Schumann resonance parameters. Journal of Atmospheric and Solar-Terrestrial Physics 66, 1179–1185]. The objective of this work is two fold: (i) to investigate the characteristics of SR parameters obtained at Şarköy in Turkey and (ii) to model the dynamical characteristics of the SR processes by forecasting the first SR mode power values using a neural network (NN) model. The NN model is revised version of the METUNN [Tulunay, Y., Tulunay, E., Senalp, E.T., 2004a. The neural network technique—1: a general exposition. Advances in Space Research 33, 983–987].

Recent studies of Schumann resonance and ELF transients

Schumann resonance (SR) is the global electromagnetic phenomenon occurring in the Earth – ionosphere cavity at frequencies of 8, 14, 20 Hz, etc (the ELF band). Phenomenon was named after the author of the pioneer publication on the planetary resonance. Since natural electromagnetic signal originates from lightning strokes distributed worldwide, parameters of oscillations reflect the average condition of ionospheric plasma, spatial distribution and current intensity of thunderstorms. ‘Regular’ lightning strokes occur at a rate of 50 events per second, and their electromagnetic radiation forms the SR background. An irregular or transient component exists caused by relatively rare powerful strokes (the rate is about one event per minute or even less) that provide pulses ten times higher than an ordinary discharge. Three orthogonal field components (vertical electric and two crossed horizontal magnetic fields) are recorded at a Schumann resonance field site, and the power spectra are obtained in the frequency band up to 40 Hz averaged over a few minutes with the typical frequency resolution of 0.1 Hz. The main objective of report is to review the recent results in the Schumann resonance studies. The report consists of two parts; one of them summarizes the experimental data obtained during last 3 – 5 years, while the second describes model studies of ELF radio propagation. We try to mention the most important results in the Schumann resonance. The report surveys the data obtained by using ‘classical’ power spectra acquired at different observatories. Power spectra give information on the properties of the lower ionosphere boundary and on the dynamics of the global thunderstorms. For instance, the sudden changes can be detected in the space weather such as Solar Proton Events (SPE); the regular seasonal motion of thunderstorms is monitored, which is associated with the ground surface temperature; unusual changes might be found in the SR spectra prior to disastrous earthquakes, etc. The cross-spectra of both magnetic fields and magnetic and electric fields (Poynting vector) might be obtained when three field components are recorded. Cross-spectra enhance the coherent fields and reduce the noise thus presenting a more exact information on both the source location and the SR parameters. Elliptical polarization of horizontal magnetic field is measured via the cross-spectra technique, and recent comparison with the model computations proved the detection of Schumann resonance line splitting. Accumulated experimental data present a wide area for resolving the inverse electromagnetic problems directed to establishing an unknown instant distribution of the global lightning activity. Resonance parameters measured worldwide allowed for constructing the effective globally averaged models of the lower ionosphere and the dispersion relation for ELF radio waves. Recent model developments are connected with applications of finite element methods to the resonance problem. Simultaneously, the ‘classical’ spectral field representation was transformed into the time domain providing an effective computational algorithm. Analytical time domain solution allowed generating the quasi–random pulse successions modeling the ELF radio noise. The model time domain ELF signals might be synthesized with predetermined properties. In the conclusion of review, we note a renewal of interest towards the extra-terrestrial Schumann resonance studies. The Huygens probe mission on Titan stimulated interest to distant detection of feasible lightning strokes at the planets and their global location by using the planetary resonance concurrently with studies of ionospheres.