Extremely Low Frequency Waves Research Articles

ELF emission in the topside ionosphere from the ZEVS transmitter detected by CSES satellite

The extremely-low-frequency (ELF) response in the upper ionosphere to ground large-scale transmitter ZEVS on the Kola Peninsula has been detected by low-Earth orbiting satellite CSES (∼500 km altitude). When the satellite was in the vicinity of the ZEVS transmitter above the White Sea (horizontal distance ∼400–900 km), the electric and magnetic sensors detected a narrowband 82 Hz emission with amplitudes E≃1-3μV/m and B≃0.5-1.0 pT. We modeled the ELF wave field spatial structure in the upper ionosphere excited by an oscillating 82 Hz linear current with the 60 km length suspended above a high-resistive ground. Realistic altitudinal profiles of the plasma parameters during events under study have been reconstructed with the use of the IRI ionospheric model. The modeled amplitudes of electromagnetic response of the upper ionosphere are in reasonable agreement with the 82-Hz emission power recorded by the CSES satellite for a typical transmitter current intensity >100 A.

Pemanfaatan Gelombang Elektromagnet Extremely Low Frequency (Elf) Dalam Ketahanan Pangan

Physics is considered an important subject that is taught as a subject in itself with various considerations. Physics is seen as both a process and a product, so successful physics learning requires attention to effective and efficient learning. The utilization of Extremely Low Frequency (ELF) electromagnetic waves has great potential in the field of food security. ELF waves have low-frequency characteristics that create a unique potential to influence microbial activity and nutrient availability in improving food security productivity. ELF waves can be used to increase the productivity and quality of food crops, as well as extend the shelf life of food products. Thus, the utilization of ELF waves can help in achieving sustainable food security. In an effort to improve food security, it is necessary to innovate and develop technology that can support agricultural productivity. More research is still needed to fully understand the mechanism of action of ELF waves and how best to use them in agricultural and food processing practices.

Long-Range EM Communication Underwater With Ultracompact ELF Magneto-Mechanical Antenna

In this article, a long-range underwater electromagnetic (EM) communication system is proposed based on an ultracompact extremely low-frequency (ELF) magnetomechanical transmission antenna (UEMTA). The transmitter mainly includes a waveform generator, a variable frequency drive (VFD), and a three-phase induction motor. The receiver consists of a 200-turn coil and signal analyzer. Based on the equivalent model of a rotating magnetic dipole, the principles of the EM transmission underwater and across the interface of water and air are analyzed. ELF wave propagating underwater in the adjacent area was stronger and decays slowly, which was certificated by the experiment and simulation. Thus, the long-range transmission underwater in the ELF band with digital coding modulation based on the UEMTA is realized, and the longest distance can reach 210 m underwater in the experiment. The transmission of ELF wave across water–air medium based on the system is also tested by the experiment too. The long-range transmission of digital coding modulation across the water–air interface is realized with the longest distance of about 210 m. The ELF transmission technology based on the UEMTA can greatly promote flexible long-distance underwater transmission, the development of satellite-to-submarine communication, and ocean exploration.

Effect of extremely low frequency (ELF) magnetic field on processing and quality of local fresh milk

This research aims to examine the effect of exposure to extremely low frequency (ELF) magnetic fields on the processing and quality of fresh milk. Furthermore, an environmentally friendly technology that does not require LPG gas or fuel was generated for handling and processing fresh milk. This research consisted of two treatments, such as the type of milk and storage time, which included 0, 5, and 19 hours. Each treatment combination was replicated three times, and the parameters observed were pH as well as the number of microbes. The result shows that exposure to ELF of 801 μT waves for 90 minutes affects the type of milk and total microbes. In addition, the pH value decreased with increasing storage time, while the total microbial value increased with increasing storage time. The use of ELF waves extends shelf life and has the potential for environmentally friendly processing of fresh milk without the use of LPG and fuel.

Multiscale modeling and simulation methods for electromagnetic and multiphysics problems

Multiscale modeling and simulation methods for electromagnetic and multiphysics problems

Two Approaches for Modeling ELF Wave Propagation in the Earth-Ionosphere Cavity With Day-Night Asymmetry

In this article, we introduce a lesser-known analytical treatment and a new numerical approach to model electromagnetic wave propagation in the lowest part of the extremely low-frequency (ELF) band (<; 100 Hz) that takes into consideration the day-night asymmetry of the Earth-ionosphere cavity. We present numerical tests showing that the two models produce practically the same output, i.e., the relative difference between them is less than 0.4%. Our result is an important step toward inferring the distribution and intensity of global lightning activity based on the Schumann resonance (SR) measurements, which is the main objective of our work.

CSES observations of ELF wave radiation excited by the EISCAT heater

Modulation heating of the ionosphere using high-power high-frequency (HF) radio waves can generate an extremely low frequency (ELF) radiation source in the ionosphere, such as amplitude-modulation (AM) heating of the auroral electrojet or using two HF radio waves to illuminate the same region of the ionosphere to form beat-wave (BW) modulation. We first present observations of ELF waves received on the China seismo-electromagnetic satellite (CSES) and on the ground simultaneously, which were excited in the European Incoherent Scatter Scientific Association (EISCAT) modulation heating experiment carried out alternately in the AM and BW modes. When the CSES passed over the EISCAT heater, ELF waves excited in the AM and BW modes were received successfully by an electric field detector on board. The comparison of the received results between the satellite and the ground demonstrates that although the intensity of the ELF signals excited in the BW mode is far lower than that in the AM mode on the ground, the ratio of ELF wave intensities between the satellite and the ground in the BW mode is significantly larger than that in the AM mode. According to the experimental results, the propagation characteristics are simulated using the full-wave method when the ELF radiation sources are located in the D and F regions in the ionosphere.

Progress in the Knowledge, Application and Influence of Extremely Low Frequency Signals

This paper describes the characteristics of contributions made by researchers worldwide in the field of ELF (extremely low frequency) waves from 1957 to 2019. The data were collected through the Scopus database and processed with analytical and bibliometric techniques. The selection of the keywords is an essential step, because ELF has a very different meaning in some areas of medicine, where it is associated with a gene. A total of 12,436 documents were worked on in 12 thematic communities according to their collaborative relationships between authors and documents. Studies included authors publishing in the different thematic areas and the country where the USA stands first with more researchers in this theme than China and Japan. Documents were analyzed from the temporal perspective, their overall contribution, means of publication, and the language of the publication. Research requires extra effort and multidisciplinary collaboration to improve the knowledge, the application, and influence of these fields.

Parametric interaction between ELF and VLF waves: 3D LSP simulation results

We have investigated a non-linear parametric interaction between Extremely Low Frequency (ELF) and Very Low Frequency (VLF) waves using the Large Scale Plasma (LSP) simulation code in three dimensions. We have forced linear modes in the plasma at ELF and VLF frequencies through a direct excitation of the wave electric field. The modes are forced using traveling plane waves which propagate at specific values of the wave-vector and frequency consistent with the whistler and Fast Magnetosonic dispersion relations. We demonstrate, using a Lagrangian fluid model in LSP, that an electromagnetic ELF wave and a quasi-electrostatic VLF wave can parametrically couple to excite electromagnetic whistler waves. We also show the formation of multiple sidebands around the carrier VLF wave. This work serves to further validate a model developed in Sotnikov et al. [J. Geophys. Res. 99, 8917 (1994); J. Geophys. Res. 96, 11363 (1991)] and adapted by Mishin and Sotnikov [Plasma Phys. Controlled Fusion 59, 124003 (2017)] to explain the observations of whistler waves in the plasmasphere [E. Mishin and V. Sotnikov, Plasma Phys. Controlled Fusion 59, 124003 (2017) and Mishin et al., Geophys. Res. Lett. 38, L21101 (2011)].

Electromagnetic Field in the Upper Ionosphere From ELF Ground‐Based Transmitter

AbstractThe feasibility of detection of electromagnetic response in the upper ionosphere to ground large‐scale extremely low frequency (ELF) transmitters (e.g., submarine communication systems) by low‐orbiting satellites is discussed. Several times when the DEMETER satellite (660 km) was in the vicinity of the ELF transmitter on the Kola Peninsula, the electric and magnetic sensors operating in a burst mode detected a narrowband 82‐Hz emission. The same emission associated with the ELF transmitter was observed by a ground‐based magnetometer. We modeled the rate of the ELF wave energy leakage into the upper ionosphere from an oscillating 82‐Hz linear current with an infinite length suspended above a high‐resistive ground. A realistic altitudinal profile of the plasma parameters has been reconstructed with the use of the IRI ionospheric model. The modeled amplitudes and polarization of electromagnetic response of the upper ionosphere are in reasonable agreement with the properties of emission recorded by the satellite.

Applied Engineering Using Schumann Resonance for Earthquakes Monitoring

For populations that may be affected, the risks of earthquakes and tsunamis are a major concern worldwide. Therefore, early detection of an event of this type in good time is of the highest priority. The observatories that are capable of detecting Extremely Low Frequency (ELF) waves (&lt;300 Hz) today represent a breakthrough in the early detection and study of such phenomena. In this work, all earthquakes with tsunami associated in history and all existing ELF wave observatories currently located worldwide are represented. It was also noticed how the southern hemisphere lacks coverage in this matter. In this work, the most suitable locations are proposed to cover these geographical areas. Also, ELF data processed obtained from the observatory of the University of Almeria in Calar Alto, Spain are shown. This is a contribution to help protect against natural disasters such as those caused by earthquakes and tsunamis.

Studies on different geophysical and extra-terrestrial events within the Earth-ionosphere cavity in terms of ULF/ELF/VLF radio waves

The space between the two spherical conducting shells, Earth surface and the lower boundary of the ionosphere, behaves as a spherical cavity in which some electromagnetic signals can propagate a long distance and is called Earth-ionosphere waveguide. Through this waveguide ultra low frequency (ULF), extremely low frequency (ELF) and very low frequency (VLF) signals can propagate efficiently with low attenuation. Resonances which occur for ELF waves due to round-the-world propagation interfering with $2n \pi $ phase difference are called Schumann resonances. Lightnings are the main sources of energy continuously producing these electromagnetic radiations from the troposphere. Some fixed frequency signals are also transmitted through the waveguide from different stations for navigation purposes. The intensity and phase of these signals at a particular position depend on the waveguide characteristics which are highly influenced by different natural events. Thus the signatures of different geophysical and extra-terrestrial events may be investigated by studying these signals through proper monitoring of the time series data using suitable techniques. In this article, we provide a review on ULF, ELF and VLF signals within the waveguide in terms of different geophysical and extra-terrestrial events like lightning, earthquakes, Leonid meteor shower, solar flares, solar eclipse, geomagnetic storms, and TLEs etc.

Wireless Transmission of MWD and LWD Signal Based on Guidance of Metal Pipes and Relay of Transceivers

A novel approach for a wireless transmission of MWD and LWD signals in lossy formations has been proposed in this paper. First, the quasi-TEM mode of the extremely low frequency (ELF) near field is excited by a voltage gap on the pipe, guided by and propagated along the metal pipe string in LWD or MWD (logging/measurement while drilling) environment. Once the signal received on the ground is weaker than a certain threshold as the drilling depth increases, a relay segment (transceiver) is installed into the pipe string to receive, amplify, and retransmit the signals to extend the transmission distance and ensure the required propagation range of the ELF wave. In this paper, the details of the transceiver antennas and the relay segment suitable for efficient coupling to quasi-TEM mode have been given first, and then, the numerical simulations of the ELF wave propagation in LWD or MWD environment and the coupling between the guided wave and the relay segment have been made to show the coupling performance of the relay segment to quasi-TEM mode quantitatively. It has been shown that the propagation attenuation of the ELF near field with the guidance of the metal pipe string is much less than that of the space wave in the same lossy media without the guidance of the pipe string, and the scheme of the wireless relay provides an efficient way to extend the propagation range of the EM telemetry evidently and open a new freedom of frequency optimization for wireless transmission systems.

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.

ELF magnetic fluctuations detected by Kaguya in deepest lunar wake associated with type-II protons

Magnetic fluctuations in the extremely low-frequency (ELF) range from 0.1 to 10 Hz were found by the Lunar Magnetometer (LMAG) of the magnetic field and plasma experiment (MAP) on board the spacecraft Kaguya in the deepest wake behind the moon, where the magnetic field is usually quiet. The fluctuations were compressional and non-monochromatic, showing no preferred polarization. They were often accompanied by “type-II entry” solar wind protons that were reflected by the dayside lunar surface or crustal magnetic field, gyrated around the solar wind magnetic field, then entered the deepest wake. The ELF waves persisted for 30 s to several minutes. The duration was often shorter than that of the type-II protons. Most of the waves were detected on the magnetic field lines disconnected from the lunar surface, along which the solar wind electrons were injected into the wake. Since a large cross-field velocity difference is expected between the type-II protons and the solar wind electrons injected along the magnetic field, some cross-field current-driven instability such as the lower hybrid two-stream instability is expected to be responsible for the generation of the waves.

Artificial excitation of ELF waves with frequency of Schumann resonance

We report results from the experiment aimed at the artificial excitation of extremely low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance. Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the Earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range 7.8–8.0Hz when the ionosphere has a strong F layer, the frequency of the HF radiation is in the range 3.20–4.57MHz, and the electric field greater than 5mV/m is present in the ionosphere.

Gyro‐resonant scattering of radiation belt electrons during the solar minimum by fast magnetosonic waves

AbstractIn the current study, we perform statistical analysis of the magnetosonic (MS) waves (also often referred to as extremely low frequency (ELF) equatorial noise) in the range between the ion cyclotron frequency and the lower hybrid resonance frequency within 10° of the magnetic equator. Observations were made between 2 and 9 RE using THEMIS Filter Bank (FBK) data. ELF waves with spectral power exceeding 10−6 nT2/Hz are registered in ~3% of all samples in the inner magnetosphere. The survey has shown that, during the solar minimum, the average amplitude of equatorial ELF waves is less than 0.025 nT. Interpreting ELF events as MS waves, we have evaluated the corresponding wave‐induced resonant scattering coefficients of radiation belt energetic electrons. We also study the effect of heavy ions on the scattering rates. The analysis reveals that the scattering by magnetosonic waves for various plasma compositions during geomagnetically quiet times is by up to two orders of magnitude slower than was previously reported and cannot significantly contribute to the long‐term dynamics of the radiation belts. Computed electron scattering rates by magnetosonic waves extends to higher αeq when the fraction of H+ in the plasma decreases, while the range of pitch angles for which resonance occurs remains relatively insensitive to the plasma composition. While inclusion of multi‐ion species into the wave dispersion relation produces noticeable changes in bounce‐averaged scattering rates, the average rates are still significantly below typical scattering rates of chorus or hiss waves.

The Characteristics of Magnetic Signals Observed at Lulin ELF Station and Their Association with Earthquakes in Taiwan

Electromagnetic wave data from years 2009 2010 which were recorded by the extremely-low-frequency (ELF) station at Lulin Observatory in Taiwan (120.87°E, 23.46°N; 2862 m) are analyzed to explore the wave properties and their association with seismic and geomagnetic activities. Specifically, the power spectra, the ellipticity and the orientation of the below-10-Hz wave signals are studied. The correlation coefficients of these ELF signals and geomagnetic activity indices Dst and Kp are within -0.2 to 0.2, indicating geomagnetic activities are not likely sources for these emissions. In the frequency versus time (f-t) spectrograms, a few events exhibit a frequency shift between 4 and 6 Hz and the possible association with seismic activities of magnitudes (M) larger than 4 in the vicinity of Taiwan are examined. The subset of earthquakes in Taiwan with M/r2 (r is the epicenter distance in kilometer from the Lulin station) of greater than 6 × 10-4, a total number of 50, show a higher association with ELF wave events showing a frequency down-shift within 7 days prior to the earthquakes and a frequency bounce-back within 7 days after the earthquakes. The epicenters of these earthquakes are all within a distance of 100 km from the Lulin station and with a depth of 50 km, suggesting that the detected ELF frequency-shift wave events maybe are pre-earthquake electromagnetic signals.

Harmonic minimization waveforms for modulated heating experiments at HAARP

Modulated High Frequency (few MHz) heating of the D‐region ionosphere under the auroral electrojet is capable of generating extremely low frequency (ELF) radio waves in the few kilohertz range by affecting the conductivity of theD‐region. The HF heating is nonlinear and results in the generation of harmonics at integer multiples of the ELF modulation frequency with ∼1% of the total power outside the fundamental when sinusoidal amplitude modulation is applied to the HF carrier. For the purpose of harmonic minimization, we present a modulation scheme designed to create a sinusoidal change in the Hall conductivity at a particular altitude in the ionosphere. The modulation waveform is generated by inverting a numerical HF heating model, starting from the desired conductivity time series, and obtaining the HF power envelope at the bottom of the ionosphere. The inverted envelopes (referred to as inv‐sin waveforms) are highly sensitive to the assumed ionospheric density profile and simulations indicate that these waveforms have less harmonic distortion compared to sinusoidal modulation when the actual ionospheric density is similar to or less dense than the one assumed. Experimental results indicate that sinusoidal amplitude modulation may still be preferred since it is more robust to the highly variable ionospheric profile while square wave modulation is more efficient in generation of ELF waves when harmonic distortion is not important. The inv‐sin waveforms are more efficient than sinusoidal modulation while still suffering from less harmonic distortion than square wave modulation suggesting a tradeoff between harmonic distortion and ELF generation efficiency.

Generation of ELF and ULF electromagnetic waves by modulated heating of the ionospheric F2 region

We present a theoretical and numerical study of the generation of extremely low frequency (ELF) and ultra‐low frequency (ULF) waves by the modulation of the electron pressure at the F2‐region with an intense high‐frequency electromagnetic wave. The study is based on a cold plasma Hall‐MHD model, including electron‐neutral and ion‐neutral collisions, which governs the dynamics of magnetostatic waves and their propagation through the ionospheric layers. Magnetosonic waves generated in the F2 region are propagating isotropically and are channeled in the ionospheric waveguide, while shear Alfvén waves are propagating along the magnetic field. To penetrate the ionosphere from the F2 peak at 300 km to the ground, the magnetostatic waves first propagate as magnetosonic or shear Alfvén waves that encounter a diffusive layer from about 150 km to 120 km where the Pedersen conductivity dominates, and then as helicon (whistler‐like) mode waves from about 120 km to 80 km where the ions are collisionally glued to the neutrals and the Hall conductivity dominates. By performing numerical simulations and studying the dispersive properties of the wave modes, we investigate the dynamics and penetration of ELF/ULF waves through the ionospheric layers to the ground and along the geomagnetic field lines to the magnetosphere. Realistic profiles of the ionospheric profiles of conductivity and density are used, together with different configurations of the geomagnetic field, relevant for both the high, mid and equatorial latitudes. Some of the results are compared with recent HAARP experiments.