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Journal articles on the topic 'ELF-VLF waves'

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Author: Grafiati

Published: 6 September 2023

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1

Barr, R., D. Llanwyn Jones, and C. J. Rodger. "ELF and VLF radio waves." Journal of Atmospheric and Solar-Terrestrial Physics 62, no. 17-18 (November 2000): 1689–718. http://dx.doi.org/10.1016/s1364-6826(00)00121-8.

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2

Chang, S. S., B. B. Ni, J. Bortnik, C. Zhou, Z. Y. Zhao, J. X. Li, and X. D. Gu. "Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification." Annales Geophysicae 32, no. 5 (May 21, 2014): 507–18. http://dx.doi.org/10.5194/angeo-32-507-2014.

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Abstract. Modulated high-frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low-frequency (ELF)/very low-frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high-energy electrons in the plasmasphere. By ray tracing the magnetospheric propagation of ELF/VLF emissions artificially generated at low-invariant latitudes, we evaluate the relativistic electron resonant energies along the ray paths and show that propagating artificial ELF/VLF waves can resonate with electrons from ~ 100 keV to ~ 10 MeV. We further implement test particle simulations to investigate the effects of resonant scattering of energetic electrons due to triggered monotonic/single-frequency ELF/VLF waves. The results indicate that within the period of a resonance timescale, changes in electron pitch angle and kinetic energy are stochastic, and the overall effect is cumulative, that is, the changes averaged over all test electrons increase monotonically with time. The localized rates of wave-induced pitch-angle scattering and momentum diffusion in the plasmasphere are analyzed in detail for artificially generated ELF/VLF whistlers with an observable in situ amplitude of ~ 10 pT. While the local momentum diffusion of relativistic electrons is small, with a rate of < 10−7 s−1, the local pitch-angle scattering can be intense near the loss cone with a rate of ~ 10−4 s−1. Our investigation further supports the feasibility of artificial triggering of ELF/VLF whistler waves for removal of high-energy electrons at lower L shells within the plasmasphere. Moreover, our test particle simulation results show quantitatively good agreement with quasi-linear diffusion coefficients, confirming the applicability of both methods to evaluate the resonant diffusion effect of artificial generated ELF/VLF whistlers.

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3

Zhima, Zeren, Yunpeng Hu, Xuhui Shen, Wei Chu, Mirko Piersanti, Alexandra Parmentier, Zhenxia Zhang, et al. "Storm-Time Features of the Ionospheric ELF/VLF Waves and Energetic Electron Fluxes Revealed by the China Seismo-Electromagnetic Satellite." Applied Sciences 11, no. 6 (March 15, 2021): 2617. http://dx.doi.org/10.3390/app11062617.

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This study reports the temporal and spatial distributions of the extremely/very low frequency (ELF/VLF) wave activities and the energetic electron fluxes in the ionosphere during an intense storm (geomagnetic activity index Dst of approximately −174 nT) that occurred on 26 August 2018, based on the observations by a set of detectors onboard the China Seismo-Electromagnetic Satellite (CSES). A good correlation of the ionospheric ELF/VLF wave activities with energetic electron precipitations during the various storm evolution phases was revealed. The strongest ELF/VLF emissions at a broad frequency band extending up to 20 kHz occurred from the near-end main phase to the early recovery phase of the storm, while the wave activities mainly appeared at the frequency range below 6 kHz during other phases. Variations in the precipitating fluxes were also spotted in correspondence with changing geomagnetic activity, with the max values primarily appearing outside of the plasmapause during active conditions. The energetic electrons at energies below 1.5 MeV got strong enhancements during the whole storm time on both the day and night side. Examinations of the half-orbit data showed that under the quiet condition, the CSES was able to depict the outer/inner radiation belt as well as the slot region well, whereas under disturbed conditions, such regions became less sharply defined. The regions poleward from geomagnetic latitudes over 50° were found to host the most robust electron precipitation regardless of the quiet or active conditions, and in the equatorward regions below 30°, flux enhancements were mainly observed during storm time and only occasionally in quiet time. The nightside ionosphere also showed remarkable temporal variability along with the storm evolution process but with relatively weaker wave activities and similar level of fluxes enhancement compared to the ones in the dayside ionosphere. The ELF/VLF whistler-mode waves recorded by the CSES mainly included structure-less VLF waves, structured VLF quasi-periodic emissions, and structure-less ELF hiss waves. A wave vector analysis showed that during storm time, these ELF/VLF whistler-mode waves obliquely propagated, mostly likely from the radiation belt toward the Earth direction. We suggest that energetic electrons in the high latitude ionosphere are most likely transported from the outer radiation belt as a consequence of their interactions with ELF/VLF waves.

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4

Platino, M., U. S. Inan, T. F. Bell, J. Pickett, E. J. Kennedy, J. G. Trotignon, J. L. Rauch, and P. Canu. "Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter." Annales Geophysicae 22, no. 7 (July 14, 2004): 2643–53. http://dx.doi.org/10.5194/angeo-22-2643-2004.

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Abstract. It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and high-altitude satellite observations have also been reported (James et al., 1990). One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere illuminated by the ELF/VLF waves. In an attempt to investigate this question further, ground-satellite conjunction experiments have recently been conducted using the four Cluster satellites and the HF heater of the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. Being located on largely closed field lines at L≈4.9, HAARP is currently also being used for ground-to-ground type of ELF/VLF wave-injection experiments, and will be increasingly used for this purpose as it is now being upgraded for higher power operation. In this paper, we describe the HAARP installation and present recent results of the HAARP-Cluster experiments. We give an overview of the detected ELF/VLF signals at Cluster, and a possible explanation of the spectral signature detected, as well as the determination of the location of the point of injection of the HAARP ELF/VLF signals into the magnetosphere using ray tracing.

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5

Guo, Zhe, Hanxian Fang, and Farideh Honary. "The Generation of ULF/ELF/VLF Waves in the Ionosphere by Modulated Heating." Universe 7, no. 2 (January 29, 2021): 29. http://dx.doi.org/10.3390/universe7020029.

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One of the most important effects of ionospheric modification by high power, high frequency (HF) waves is the generation of ultra low frequency/extremely low frequency/very low frequency (ULF/ELF/VLF) waves by modulated heating. This paper reviews the scientific achievements of the past five decades regarding the main mechanisms of excitation of ULF/ELF/VLF waves and discusses their characteristics, such as their electrojet dependency, the location of the source region, continuous and discontinuous waves, the number of HF arrays, and the suitable range of the modulation frequency for different proposed mechanisms. Finally, the outlook for future research in this area is presented.

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6

Błęcki, Jan, Roman Wronowski, Jan Słomiński, Sergey Savin, Rafał Iwański, and Roger Haagmans. "Comparative Study of the Energetic Electrons Registered Together with the Broad Band Emissions in Different Regions of the Ionosphere." Artificial Satellites 55, no. 4 (December 1, 2020): 130–49. http://dx.doi.org/10.2478/arsa-2020-0010.

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Abstract ELF/VLF waves have been registered in the outer polar cusps simultaneously with high energy electrons fluxes by the satellites Magion 4 (subsatellite to Interball 1), Polar and CLUSTER. Further, we discuss similar observations in the different regions of the ionosphere, where DEMETER registered energetic electrons. The DEMETER satellite operating on the nearly polar orbit at the altitude 650 km crossed different regions in the ionosphere. Registrations of ELF/VLF/HF waves together with the energetic electrons in the polar cusp, in the ionospheric trough and over thunderstorm areas are presented in this paper. The three satellites of ESA’s Swarm mission provide additional information on the ELF waves in the mentioned areas together with electron density and temperature. A brief discussion of the generation of these emissions by the so-called “fan instability” (FI) and beam instability is presented.

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7

Hayakawa, M., A. Schekotov, J. Izutsu, and A. P. Nickolaenko. "Seismogenic effects in ULF/ELF/VLF electromagnetic waves." INTERNATIONAL JOURNAL OF ELECTRONICS AND APPLIED RESEARCH 06, no. 02 (August 22, 2019): 1–86. http://dx.doi.org/10.33665/ijear.2019.v06i02.001.

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8

Koshevaya, S., N. Makarets, V. Grimalsky, A. Kotsarenko, and R. Perez Enríquez. "Spectrum of the seismic-electromagnetic and acoustic waves caused by seismic and volcano activity." Natural Hazards and Earth System Sciences 5, no. 2 (February 2, 2005): 203–9. http://dx.doi.org/10.5194/nhess-5-203-2005.

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Abstract. Modeling of the spectrum of the seismo-electromagnetic and acoustic waves, caused by seismic and volcanic activity, has been done. This spectrum includes the Electromagnetic Emission (EME, due to fracturing piezoelectrics in rocks) and the Acoustic Emission (AE, caused by the excitation and the nonlinear passage of acoustic waves through the Earth's crust, the atmosphere, and the ionosphere). The investigated mechanism of the EME uses the model of fracturing and the crack motion. For its analysis, we consider a piezoelectric crystal under mechanical stresses, which cause the uniform crack motion, and, consequently, in the vicinity of the moving crack also cause non-stationary polarization currents. A possible spectrum of EME has been estimated. The underground fractures produce Very Low (VLF) and Extremely Low Frequency (ELF) acoustic waves, while the acoustic waves at higher frequencies present high losses and, on the Earth's surface, they are quite small and are not registered. The VLF acoustic wave is subject to nonlinearity under passage through the lithosphere that leads to the generation of higher harmonics and also frequency down-conversion, namely, increasing the ELF acoustic component on the Earth's surface. In turn, a nonlinear propagation of ELF acoustic wave in the atmosphere and the ionosphere leads to emerging the ultra low frequency (ULF) acousto-gravity waves in the ionosphere and possible local excitation of plasma waves.

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9

DOWDEN, Richard L. "Generation of VLF and ELF waves for active probing." Journal of geomagnetism and geoelectricity 40, no. 10 (1988): 1131–40. http://dx.doi.org/10.5636/jgg.40.1131.

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10

Chen, Jing, Jutao Yang, Qingliang Li, Yubo Yan, Shuji Hao, Cheng Wang, Jian Wu, et al. "ELF/VLF Wave Radiation Experiment by Modulated Ionospheric Heating Based on Multi-Source Observations at EISCAT." Atmosphere 13, no. 2 (January 29, 2022): 228. http://dx.doi.org/10.3390/atmos13020228.

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Ground-based high-frequency modulated waves can periodically heat the ionosphere and create “virtual antennas”, which can radiate extremely low frequency (ELF, 0.3–3 kHz) or very low frequency (VLF, 3–30 kHz) waves for long-distance communication. Ionospheric X-mode and O-mode heating experiments using amplitude and beat-wave (BW) modulations were conducted on 21 November 2019. Experimental results were analyzed from multiple perspectives based on data from Dynasonde, a magnetometer, stimulated electromagnetic emissions, an ELF/VLF signal receiver, and ultra-high-frequency radar. The strongest excited ELF/VLF signals in previous BW modulation heating experiments were around 8–12 kHz; however, in this experiment, no signal excited in this frequency range was observed, and the signal with the highest signal/noise ratio was at the frequency of 3517 Hz, which will aid in understanding the best communication frequency under different ionospheric backgrounds. It is well-accepted that the electron temperature changes periodically with the modulation frequency. However, we noted that the electron temperature had insufficient cooling during the O-mode modulated heating process and then increased again, resulting in a continuous electron temperature increase. We found that this was related to the change in ion composition after analyzing ion-line spectra, which will be helpful in studying the effect of modulation heating on the ionosphere background.

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11

Trakhtengerts, V. Y. "A generation mechanism for chorus emission." Annales Geophysicae 17, no. 1 (January 31, 1999): 95–100. http://dx.doi.org/10.1007/s00585-999-0095-4.

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Abstract. A chorus generation mechanism is discussed, which is based on interrelation of ELF/VLF noise-like and discrete emissions under the cyclotron wave-particle interactions. A natural ELF/VLF noise radiation is excited by the cyclotron instability mechanism in ducts with enhanced cold plasma density or at the plasmapause. This process is accompanied by a step-like deformation of the energetic electron distribution function in the velocity space, which is situated at the boundary between resonant and nonresonant particles. The step leads to the strong phase correlation of interacting particles and waves and to a new backward wave oscillator (BWO) regime of wave generation, when an absolute cyclotron instability arises at the central cross section of the geomagnetic trap, in the form of a succession of discrete signals with growing frequency inside each element. The dynamical spectrum of a separate element is formed similar to triggered ELF/VLF emission, when the strong wavelet starts from the equatorial plane. The comparison is given of the model developed using some satellite and ground-based data. In particular, the appearance of separate groups of chorus signals with a duration 2-10 s can be connected with the preliminary stage of the step formation. BWO regime gives a succession period smaller than the bounce period of energetic electrons between the magnetic mirrors and can explain the observed intervals between chorus elements.Key words. Magnetospheric physics (Energetic particles · trapped). Space plasma physics (wave-particle interactions; waves and instabilities)

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12

CHANG, Shan-Shan, Zheng-Yu ZHAO, and Feng WANG. "Downward ELF/VLF Waves Radiation Excited by Ionospheric Artificial Modulation." Chinese Journal of Geophysics 54, no. 5 (September 2011): 649–59. http://dx.doi.org/10.1002/cjg2.1648.

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13

Guo, Zhe, Hanxian Fang, and Farideh Honary. "A Novel Method to Identify the Physical Mechanism and Source Region of ELF/VLF Waves Generated by Beat-Wave Modulation Using Preheating Technique." Universe 7, no. 2 (February 15, 2021): 43. http://dx.doi.org/10.3390/universe7020043.

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One of the most important effects of ionospheric heating by HF (high-frequency) waves is the generation of ELF/VLF (extremely low-frequency/very low-frequency) waves by modulated heating. An important limitation of amplitude modulation (AM) is its dependence on ionospheric electrojet, which means to achieve better modulation effect, some strict spatio-temporal conditions must be met. To solve this problem, some possible methods have been proposed including beat-wave (BW) modulation. However, due to the controversy of its mechanism and the source region of the stimulated ELF/VLF waves, it is not clear whether it is an electrojet-independent method or not, which has become one of the hot topics in recent years. In this paper, we found that the effect of preheating on modulation efficiency of BW based on different theories is the opposite. We suppose the opposite character of the influence and effect on the efficiency of BW in D region and F region as a base for a novel method to identify the physical mechanism and source region of BW. This method can be feasible to solve the controversy of BW. The feasibility of this method is verified by simulation results in the paper.

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14

Błęcki, J., M. Parrot, and R. Wronowski. "ELF and VLF signatures of sprites registered onboard the low altitude satellite DEMETER." Annales Geophysicae 27, no. 6 (June 29, 2009): 2599–605. http://dx.doi.org/10.5194/angeo-27-2599-2009.

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Abstract. We report the observation of ELF and VLF signature of sprites recorded on the low altitude satellite DEMETER during thunderstorm activity. At an altitude of ~700 km, waves observed on the E-field spectrograms at mid-to-low latitudes during night time are mainly dominated by up-going 0+ whistlers. During the night of 20 July 2007 two sprites have been observed around 20:10:08 UT from the observatory located on the top of the mountain Śnieżka in Poland (50°44'09" N, 15°44'21" E, 1603 m) and, ELF and VLF data have been recorded by the satellite at about 1200 km from the region of thunderstorm activity. During this event, the DEMETER instruments were switched in the burst mode and it was possible to register the wave forms. It is shown that the two sprites have been triggered by two intense +CG lightning strokes (100 kA) occurring during the same millisecond but not at the same location. Despite the distance DEMETER has recorded at the same time intense and unusual ELF and VLF emissions. It is shown that the whistler wave propagates from the thunderstorm regions in the Earth-ionosphere guide and enters in the ionosphere below the satellite. They last several tens of milliseconds and the intensity of the ELF waveform is close to 1 mV/m. A particularly intense proton whistler is also associated with these emissions.

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15

Martinez-Calderon, Claudia, Kazuo Shiokawa, Yoshizumi Miyoshi, Mitsunori Ozaki, Ian Schofield, and Martin Connors. "Polarization analysis of VLF/ELF waves observed at subauroral latitudes during the VLF-CHAIN campaign." Earth, Planets and Space 67, no. 1 (2015): 21. http://dx.doi.org/10.1186/s40623-014-0178-7.

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16

Gorishnya, Yulia, and Alisa Shvets. "Correlational Analysis of the ELF – VLF Nighttime Atmospherics Parameters." Ukrainian journal of remote sensing 9, no. 4 (December 8, 2022): 4–12. http://dx.doi.org/10.36023/ujrs.2022.9.4.218.

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Tweek-atmospherics (tweeks), along with radio transmission by VLF radio stations, are used to study the lower ionosphere. Electromagnetic pulse radiation, which has been excited by the lightning discharges, has a maximum spectral density at extra low frequencies range (ELF, 300...3000 Hz) and very low frequencies (VLF, 3...30 kHz). The Earth-ionosphere cavity serves as a waveguide for electromagnetic waves in these frequency ranges. On the spectrogram of the tweek, the initial part is a linearly polarized broadband signal, and then a number of individual harmonics are observed. Their instantaneous frequencies decrease, asymptotically approaching approximately multiples of the cutoff frequencies of the waveguide. The single position method for lightning location and estimation of the ELF wave’s reflection heights in the lower ionosphere by tweeks has been implemented into the computational algorithm. The clusters with approximately the same azimuths and distances to sources which have been obtained during the same night have been identified upon the ensemble of tweek-atmospheric records. The data were accumulated at the Ukrainian Antarctic Station "Akademik Vernadsky" in 2019. The location of the receiving complex in the near-polar region makes it possible to register tweek sources in two world thunderstorm centers with geographic azimuths from –60° to 130°. The results of processing these data have been used by studying the correlation matrix and partial correlation coefficients to identify causal relationships between the three main parameters of the tweek, such as (1) the average azimuth of the arrival of tweeks in regard to the magnetic meridian, (2) the average distance to the center of the cluster of tweek sources (lightning discharges), and (3) the average number of tweek harmonics. The same correlation analysis was applied to two groups with distances to sources of 2.2...7.5 Mm and 7.6...9.5 Mm used for study in detail. It is shown that the partial correlation coefficients between the number of tweek harmonics and the difference of the magnetic azimuth from the magnetic east are 0.624 (for the entire range of distances), 0.696 (for far tweek sources) and 0.595 (for main middle range), so, they always exceed the values of 0.1% significance level. The correlation of tweek spectrum with the distance to the tweek source in the range of 2.2…7.5 Mm has been shown to be comparable in magnitude or to exceed the correlation of tweek spectrum with the magnetic azimuth. The elimination of this masking effect by calculating the partial correlation coefficients made it possible to reveal the magnetic azimuth dependences of the tweek spectra if tweek propagates in a region outside the geomagnetic equator. Thus, the effect of non-reciprocity of propagation of ELF – VLF waves in regard to the magnetic meridian in the east – west and west – east directions is found in the spectra of tweek-atmospherics. It results in an increased probability of detecting tweeks with higher harmonics if their directions of arrival are close to the geomagnetic east. It is also shown that this effect, as a result of increased attenuation during the propagation of ELF – VLF radiation from the west and weakened attenuation during propagation from the east, leads to a highly significant correlation (with probability level more than 99.9%) between the magnetic azimuths of tweeks and the lengths of their paths to the receiving station.

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17

Tsurutani, Bruce T., Armando L. Brinca, Edward J. Smith, Roy T. Okida, Roger R. Anderson, and Timothy E. Eastman. "A statistical study of ELF-VLF plasma waves at the magnetopause." Journal of Geophysical Research 94, A2 (1989): 1270. http://dx.doi.org/10.1029/ja094ia02p01270.

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18

Nagai, Ken, Kenji Ohta, Yasuhide Hobara, and Masashi Hayakawa. "Transmission characteristics of VLF/ELF radio waves through the Jovian ionosphere." Geophysical Research Letters 20, no. 22 (November 19, 1993): 2435–38. http://dx.doi.org/10.1029/93gl02845.

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19

Main, D., and V. Sotnikov. "Parametric interaction between ELF and VLF waves: 3D LSP simulation results." Physics of Plasmas 27, no. 2 (February 2020): 022304. http://dx.doi.org/10.1063/1.5126675.

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20

Zhima, Zeren, JinBin Cao, WenLong Liu, HuiShan Fu, TieYan Wang, XueMin Zhang, and XuHui Shen. "Storm time evolution of ELF/VLF waves observed by DEMETER satellite." Journal of Geophysical Research: Space Physics 119, no. 4 (April 2014): 2612–22. http://dx.doi.org/10.1002/2013ja019237.

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21

Agapitov, O., V. Krasnoselskikh, Yu Zaliznyak, V. Angelopoulos, O. Le Contel, and G. Rolland. "Observations and modeling of forward and reflected chorus waves captured by THEMIS." Annales Geophysicae 29, no. 3 (March 11, 2011): 541–50. http://dx.doi.org/10.5194/angeo-29-541-2011.

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Abstract. Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts of the Earth's magnetosphere. Chorus emissions, whistler-mode wave packets propagating roughly along magnetic field lines from a well-localized source in the vicinity of the magnetic equator to polar regions, can be reflected at low altitudes. After reflection, wave packets can return to the equatorial plane region. Understanding of whistler wave propagation and reflection is critical to a correct description of wave-particle interaction in the radiation belts. We focus on properties of reflected chorus emissions observed by the THEMIS (Time History of Events and Macroscale Interactions During Substorms) spacecraft Search Coil Magnetometer (SCM) and Electric Field Instrument (EFI) at ELF/VLF frequencies up to 4 kHz at L≥8. We determine the direction of the Poynting flux and wave vector distribution for forward and reflected chorus waves. Although both types of chorus waves were detected near the magnetic equator and have similar, discrete structure and rising tones, reflected waves are attenuated by a factor of 10–30 and have 10% higher frequency than concurrently-observed forward waves. Modeling of wave propagation and reflection using geometrical optics ray-tracing allowed us to determine the chorus source region location and explain observed propagation characteristics. We find that reflected wave attenuation at a certain spatial region is caused by divergence of the ray paths of these non-ducted emissions, and that the frequency shift is caused by generation of the reflected waves at lower L-shells where the local equatorial gyrofrequency is larger.

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22

Lin, N., E. S. Lee, J. McFadden, G. Parks, M. Wilber, M. Maksimovic, N. Cornilleau-Wehrlin, et al. "VLF/ELF wave activity in the vicinity of the polar cusp: Cluster observations." Annales Geophysicae 24, no. 7 (August 9, 2006): 1993–2004. http://dx.doi.org/10.5194/angeo-24-1993-2006.

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Abstract. Observations by the Cluster spacecraft of VLF/ELF wave activity show distinct signatures for different regions in the vicinity of high altitude polar cusps, which are identified by using magnetic field and plasma data along spacecraft trajectories. These waves include: (1) Broad band magnetic noise observed in the polar cusp at frequencies from several Hz to ~100 Hz, below the local electron cyclotron frequency, fce. Similar magnetic noise is also observed in the high latitude magnetosheath and the magnetopause boundary layer. (2) Strong broad band electrostatic emissions observed in the cusp, in the magnetosheath, and in the high latitude magnetopause boundary layer, at frequencies extending from several Hz to tens of kHz, with maximum intensities below ~100 Hz. (3) Narrow-band electromagnetic whistler waves at frequencies ~0.2–0.6 fce, frequently observed in the closed boundary layer (CBL) adjacent to the polar cusp. These waves are for the first time observed in this region to be accompanied by counter-streaming electron beams of ~100 eV, which suggests that the waves are excited by these electrons through wave-particle interaction. (4) Narrow-band electrostatic waves observed slightly above the local fce in the CBL. (5) Lion roars, observed in the high latitude magnetosheath, often in magnetic troughs of mirror mode oscillations. The above wave signatures can serve as indicators of the regions in the vicinity of the magnetospheric cusp.

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23

Morrison, K., M. J. Engebretson, J. R. Beck, J. E. Johnson, R. L. Arnoldy, L. J. Cahill, D. L. Carpenter, and M. Gallani. "A study of quasi-periodic ELF-VLF emissions at three Antarctic stations: evidence for off-equatorial generation?" Annales Geophysicae 12, no. 2/3 (January 31, 1994): 139–46. http://dx.doi.org/10.1007/s00585-994-0139-8.

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Abstract. The spatial extent and temporal behaviour of quasi-periodic (QP) intensity modulations of 0.5-2 kHz ELF-VLF signals were investigated in a comparative study of data collected at the Antarctic stations of South Pole (L=14), Halley (L=4), and Siple (L=4). Frequently, the waveforms of ELF-VLF signals simultaneously received at each site were identical. Although of similar frequency structure, the waveforms of the accompanying Pc3 magnetic pulsations did not show a one-to-one association. Whereas both are dayside phenomena, QP emissions occur over a smaller range of local times, and have a maximum of occurrence later in the day closer to local noon. QP emissions are identified with the periodic modulation of the electron pitch-angle distribution by the propagation of ULF compressional fast-mode waves through a region. However, contrary to previous ideas, rising-tone emissions do not represent the frequency-time signatures of such waves. In addition to generation close to the equatorial plane, we propose an additional high-latitude source of QP emissions. These emissions are associated with regions of minimum B produced by the dayside compression of the magnetosphere close to the magnetopause. Model magnetic field calculations of these minimum-B regions as a function of magnetic local time and invariant latitude are presented.

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24

Rietveld, M. T., H. P. Mauelshagen, P. Stubbe, H. Kopka, and E. Nielsen. "The characteristics of ionospheric heating-produced ELF/VLF waves over 32 hours." Journal of Geophysical Research 92, A8 (1987): 8707. http://dx.doi.org/10.1029/ja092ia08p08707.

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25

Chmyrev, V. M., A. Berthelier, N. V. Jorjio, J. J. Berthelier, J. M. Bosqued, Yu I. Galperin, R. A. Kovrazhkin, et al. "Non-linear Alfven wave generator of auroral particles and ELF/VLF waves." Planetary and Space Science 37, no. 6 (June 1989): 749–59. http://dx.doi.org/10.1016/0032-0633(89)90044-5.

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26

KUO, S. P. "Generation of extra and very low-frequency (ELF/VLF) radiation by ionospheric electrojet modulation using high-frequency (HF) heating waves." Journal of Plasma Physics 68, no. 4 (May 2002): 267–84. http://dx.doi.org/10.1017/s0022377802001964.

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Extra and very low-frequency (ELF/VLF) wave generation by modulated polar electrojet currents is studied numerically. Through Ohmic heating by the amplitude-modulated high-frequency heating wave, the conductivity and thus the current of the electrojet are modulated accordingly to set up the ionospheric antenna current. Stimulated thermal instability, which can further enhance the electrojet current modulation, is studied. It is first analysed analytically to determine the threshold heating power for its excitation. The nonlinear evolutions of the generated ELF/VLF waves enhanced by the instability are then studied numerically. Their spectra are also evaluated. The field intensity of the emission at the fundamental modulation frequency is found to increase with the modulation frequency in agreement with the Tromso observations. The efficiency enhancement by the stimulated thermal instability is hampered by inelastic collisions of electrons with neutral particles (mainly due to vibration excitation of N2), which cause this instability to saturate at low levels. However, the electron inelastic collision loss rate drops rapidly to a low value in the energy regime from 3.5 to 6 eV. As the heating power exceeds a threshold level, significant electron heating enhanced by the instability is shown, which indeed causes a steep drop in the electron inelastic collision loss rate. Consequently, this instability saturates at a much higher level, resulting to a near step increase (of about 10–13 dB depending on the modulation wave form) in the spectral intensity of ELF radiation. The dependence of the threshold power of the HF heating wave on the modulation frequency is determined.

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Yu, Hui Min. "Characteristics Analysis for the Spherical Antenna of a Seismometer." Advanced Materials Research 171-172 (December 2010): 458–61. http://dx.doi.org/10.4028/www.scientific.net/amr.171-172.458.

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A seismometer for vertical electric field component of natural ELF and ULF electromagnetic waves measurement by using spherical antenna is introduced. The goal of the proposed seismometer is to provide continuous observation of the natural electromagnetic emissions related to the coupling of seismic activity with the outer spaces and ionosphere, which utilize a spherical aluminum electrode 78mm in diameter with embedded enhanced preamplifier circuits that built to mount flush with the ground so as to preserve the configuration in which the antenna operates. The presented seismometer has a wide frequency response at low frequencies, it's typical sensitivity in the frequency range DC to 30MHz are shown to be and ,the dynamical range is >50dB in ELF and VLF and about 25dB in HF.

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28

Pokhotelov, D., F. Lefeuvre, R. B. Horne, and N. Cornilleau-Wehrlin. "Survey of ELF-VLF plasma waves in outer radiation belt observed by Cluster STAFF-SA experiment." Annales Geophysicae 26, no. 11 (October 21, 2008): 3269–77. http://dx.doi.org/10.5194/angeo-26-3269-2008.

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Abstract. Various types of plasma waves have profound effects on acceleration and scattering of radiation belt particles. For the purposes of radiation belt modeling it is necessary to know statistical distributions of plasma wave parameters. This paper analyzes four years of plasma wave observations in the Earth's outer radiation belt obtained by the STAFF-SA experiment on board Cluster spacecraft. Statistical distributions of spectral density of different plasma waves observed in ELF-VLF range (chorus, plasmaspheric hiss, magnetosonic waves) are presented as a function of magnetospheric coordinates and geomagnetic activity indices. Comparison with other spacecraft studies supports some earlier conclusions about the distribution of chorus and hiss waves and helps to remove the long-term controversy regarding the distribution of equatorial magnetosonic waves. This study represents a step towards the development of multi-spacecraft database of plasma wave activity in radiation belts.

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29

Hegai, Valery, Zhima Zeren, and Sergey Pulinets. "Seismogenic Field in the Ionosphere before Two Powerful Earthquakes: Possible Magnitude and Observed Ionospheric Effects (Case Study)." Atmosphere 14, no. 5 (April 30, 2023): 819. http://dx.doi.org/10.3390/atmos14050819.

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A retrospective analysis of complex geophysical data around the time of the two most powerful earthquakes that occurred in Alaska and had magnitudes M = 8.2 (29 July 2021) and M = 9.2 (28 March 1964), respectively, is carried out. The aim of the research is to assess the maximum possible magnitude of the electric field of a seismogenic nature that penetrated the ionosphere/plasmasphere, which could cause the ionospheric effects observed experimentally. Theoretical calculations have shown that under the geophysical conditions that existed before these earthquakes (favorable for the penetration of the seismogenic field into the ionosphere), the maximum value of a quasi-static electric seismogenic field in the ionosphere, perpendicular to geomagnetic field lines (tens of hours/units of days before the earthquake) for earthquakes with magnitudes M = 8–9 could reach 1–2 mV/m. Such values are sufficient for the formation of a plasmaspheric ULF-ELF-VLF-duct, which is formed in the vicinity of the geomagnetic field-line passing through the epicenter of the earthquake under the influence of a seismogenic electric field that penetrated into the ionosphere/plasmasphere. This leads to an anomalous amplification of the captured ULF-ELF-VLF waves, ULF (DC-16 Hz), ELF (6 Hz–2.2 kHz), VLF (1.8–20 kHz), not only above the epicenter of the future earthquake, but also at the point magnetically conjugated with the epicenter of the earthquake, testifying to the formation of such a duct, stretched along the geomagnetic field from one hemisphere to another, and formed on closed L-shells shortly before the earthquake. This result is confirmed by the measurements of the mission of the CSES satellite (China-Seismo-Electromagnetic Satellite) for the 29 July 2021 earthquake with magnitude M = 8.2.

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30

Rietveld, M. T., P. Stubbe, and H. Kopka. "On the frequency dependence of ELF/VLF waves produced by modulated ionospheric heating." Radio Science 24, no. 3 (May 1989): 270–78. http://dx.doi.org/10.1029/rs024i003p00270.

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31

Mizonova, Vera G., and Peter A. Bespalov. "Whistler waves produced by monochromatic currents in the low nighttime ionosphere." Annales Geophysicae 39, no. 3 (June 9, 2021): 479–86. http://dx.doi.org/10.5194/angeo-39-479-2021.

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Abstract. We use a full-wave approach to find the field of monochromatic whistler waves, which are excited and propagating in the low nighttime ionosphere. The source current is located in the horizontal plane and can have arbitrary finite distribution over horizontal coordinates. The ground-based horizontal magnetic field and electric field at 125 km are calculated. The character of wave polarization on the ground surface is investigated. The proportion in which source energy supplies the Earth–ionosphere waveguide or flows upward can be adjusted by distribution of the source current. Received results are important for the analysis of ELF/VLF emission phenomena observed both on the satellites and on the ground.

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32

Xu, Tong, Michael Rietveld, Jian Wu, Guanglin Ma, Yanli Hu, Jun Wu, and Qingliang Li. "Polarization analysis of ELF/VLF waves generated by beating of two HF waves in the polar ionosphere." Journal of Atmospheric and Solar-Terrestrial Physics 196 (December 2019): 105133. http://dx.doi.org/10.1016/j.jastp.2019.105133.

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33

Ostapenko, A. A., E. E. Titova, A. P. Nickolaenko, T. Turunen, J. Manninen, and T. Raita. "Characteristics of VLF atmospherics near the resonance frequency of the Earth-ionosphere waveguide 1.6–2.3 kHz by observations in the auroral region." Annales Geophysicae 28, no. 1 (January 20, 2010): 193–202. http://dx.doi.org/10.5194/angeo-28-193-2010.

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Abstract. Recordings of ELF-VLF waves with the right-hand (RH) and the left-hand (LH) circular polarization were made in Northern Finland. Analysis showed a difference between the RH and LH polarized waves. A pronounced maximum of the wave amplitude was observed at the first critical frequency of the Earth-ionosphere waveguide (the first transverse resonance) around 1.6–2.3 kHz. The wave had the circular LH polarization at this maximum. To interpret observations, we computed the characteristics of the waveguide modes by using the full wave solution in the night model of the ionosphere. Computations show that the spectral maximum at the first transverse resonance frequency arises from a small absorption of the LH polarized radio wave in the magnetized ionosphere plasma, forming the upper boundary of the Earth-ionosphere waveguide.

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34

Markov, G. A., A. S. Belov, G. P. Komrakov, and M. Parrot. "Excitation of guided ELF-VLF waves through modification of the F2 ionospheric layer by high-power radio waves." Plasma Physics Reports 38, no. 3 (March 2012): 219–24. http://dx.doi.org/10.1134/s1063780x12020079.

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35

Yahnin, A. G., E. E. Titova, A. G. Demekhov, T. A. Yahnina, T. A. Popova, A. Lyubchich, J. Manninen, and T. Raita. "Simultaneous Observations of EMIC Waves, ELF/VLF Waves, and Energetic Particle Precipitation during Multiple Compressions of the Magnetosphere." Geomagnetism and Aeronomy 59, no. 6 (November 2019): 668–80. http://dx.doi.org/10.1134/s0016793219060148.

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36

Wakabayashi, M., T. Ono, H. Mori, and P. A. Bernhardt. "Electron density and plasma waves in mid-latitude sporadic-<i>E</i> layer observed during the SEEK-2 campaign." Annales Geophysicae 23, no. 7 (October 13, 2005): 2335–45. http://dx.doi.org/10.5194/angeo-23-2335-2005.

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Abstract. The SEEK-2 campaign was carried out over Kyushu Island in Japan on 3 August 2002, by using the two sounding rockets of S310-31 and S310-32. This campaign was planned to elucidate generation mechanisms of Quasi-Periodic Echoes (QPEs) associated with mid-latitude sporadic-E (Es) layers. Electron number densities were successfully measured in the Es layers by using the impedance probe on board two rockets. The plasma waves in the VLF and ELF ranges were also observed on board the S310-32 rocket. Results of electron density measurement showed that there were one or two major peaks in the Es layers along the rockets' trajectories near the altitude of about 10km. There were some smaller peaks associated with the main Es layers in the altitude range from 90 to 120 km. These density peaks were distributed in a very large extent during the SEEK-2 campaign. The Es layer structure is also measured by using the Fixed Bias Probe (FBP), which has a high spatial resolution of several meters (the impedance probe has an altitude resolution of about 400 m). The comparison with the total electron content (TEC) measured by the Dual Band Beacon revealed that the Es layer was also modulated in the horizontal direction with the scale size of 30–40 km. It was shown that the QP echoes observed by the ground-based coherent radar come from the major density peak of the Es layer. The plasma wave instrument detected the enhancement of VLF and ELF plasma waves associated with the operation of the TMA release, and also with the passage of the Es layers. Keywords. Ionosphere (Ionospheric irregularities; Midlatitude ionosphere; Plasma temeperature and density)

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37

James, H. G., U. S. Inan, and M. T. Rietveld. "Observations on the DE 1 spacecraft of ELF/VLF waves generated by an ionospheric heater." Journal of Geophysical Research 95, A8 (1990): 12187. http://dx.doi.org/10.1029/ja095ia08p12187.

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38

Yang, Jutao, Jianguo Wang, Qingliang Li, Jian Wu, Haiqin Che, Guanglin Ma, and Shuji Hao. "Experimental comparisons between AM and BW modulation heating excitation of ELF/VLF waves at EISCAT." Physics of Plasmas 26, no. 8 (August 2019): 082901. http://dx.doi.org/10.1063/1.5095537.

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39

Barr, R. "The generation of ELF and VLF radio waves in the ionosphere using powerful HF transmitters." Advances in Space Research 21, no. 5 (January 1998): 677–87. http://dx.doi.org/10.1016/s0273-1177(97)01003-x.

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40

Morrison, K., and M. P. Freeman. "The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions." Annales Geophysicae 13, no. 11 (November 30, 1995): 1127–33. http://dx.doi.org/10.1007/s00585-995-1127-3.

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Abstract. Recent work suggests that the quasi-periodic (QP) modulation ~10–50 s of naturally occurring ELF-VLF radio emissions (~0.5–5 kHz) is produced by the compressional action of Pc3 magnetic pulsations on the source of the emissions. Whilst it is generally accepted that these magnetic pulsations have an exogenic source, it is not clear what the mechanism of their generation is. A study of QP emissions observed during 1988 at Halley, Antarctica, in conjunction with IMP-8 satellite solar wind data, shows that the occurrence and modulation frequency of the emissions are strongly dependent upon the direction and strength of the IMF, respectively. The observed relationships are very similar to those previously reported for Pc3 pulsations associated with upstream ion-cyclotron resonance, involving proton beams reflected at the bowshock. In comparing the observed QP modulation frequencies with upstream wave theory, agreement was found by considering wave excitation exclusively associated with a proton beam reflected from a position on the bowshock at which the shock normal is parallel to the ambient IMF direction. Other geometries were found to be either impropitious or uncertain. The work indicates the useful diagnostic role QP emissions could play in the study of compressional ULF waves in the upstream solar wind and in monitoring the IMF conditions responsible for their generation.

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41

Kasahara, Yoshiya, Tomohisa Hosoda, Toshifumi Mukai, Shigeto Watanabe, Iwane Kimura, Hirotsugu Kojima, and Ryotaro Niitsu. "ELF/VLF waves correlated with transversely accelerated ions in the auroral region observed by Akebono." Journal of Geophysical Research: Space Physics 106, A10 (October 1, 2001): 21123–36. http://dx.doi.org/10.1029/2000ja000318.

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42

Xiao, FuLiang, QiuGang Zong, ZhenPeng Su, Tian Tian, and HuiNan Zheng. "Latest progress on interactions between VLF/ELF waves and energetic electrons in the inner magnetosphere." Science China Earth Sciences 53, no. 3 (January 20, 2010): 317–26. http://dx.doi.org/10.1007/s11430-010-0007-1.

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43

Takeshita, Yuhei, Kazuo Shiokawa, Mitsunori Ozaki, Jyrki Manninen, Shin‐Ichiro Oyama, Martin Connors, Dmitry Baishev, Vladimir Kurkin, and Alexey Oinats. "Longitudinal Extent of Magnetospheric ELF/VLF Waves using Multipoint PWING Ground Stations at Subauroral Latitudes." Journal of Geophysical Research: Space Physics 124, no. 12 (December 2019): 9881–92. http://dx.doi.org/10.1029/2019ja026810.

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44

Kuo, S. P., S. H. Lee, D. Bivolaru, P. Kossey, M. C. Lee, R. J. Riddolls, P. Jastrzebski, and D. Sentman. "Experimental and Numerical Studies on ELF/VLF Wave Generation by Amplitude-Modulated HF Heating Waves." Physica Scripta 67, no. 5 (January 1, 2003): 448–52. http://dx.doi.org/10.1238/physica.regular.067a00448.

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45

Lefeuvre, F., M. Parrot, J. L. Rauch, B. Poirier, A. Masson, and M. Mogilevsky. "Preliminary results from the MEMO multicomponent measurements of waves on-board INTERBALL 2." Annales Geophysicae 16, no. 9 (September 30, 1998): 1117–36. http://dx.doi.org/10.1007/s00585-998-1117-3.

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Abstract. The MEMO (MEsure Multicomposante des Ondes) experiment is a part of the INTERBALL 2 wave consortium. It is connected to a total of six electric and nine magnetic independent sensors. It provides waveforms associated with the measurement of two to five components in three frequency bands: ELF (5–1000 Hz), VLF (1–20 kHz), LF (20–250 kHz). Preliminary analyses of low and high resolution data are presented. The emphasis is put on the estimation of the propagation characteristics of the observed waves.VLF hiss emissions are shown to be mainly whistler mode emissions, but other modes are present. An accurate estimation of the local plasma frequency is proposed when the low L = 0 cutoff frequency is identified. AKR emissions observed just above source regions are studied. R-X and L-O modes are found: the first at the lowest frequencies and the second at the highest. Both propagate with wave normal directions weakly oblique or quasi-parallel to the Earth's magnetic field direction. Propagation characteristics are also determined for a (non-drifting) fine structure of AKR. There is no fundamental difference with structurless events. Nightside and dayside bursts of ELF electromagnetic emissions are presented. It is not clear whether the two emissions belong to the "lion roar" emissions or not.Key words. Magnetospheric physics (auroral phenomena; plasma waves and instabilities; instruments and techniques)

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46

Luo, Yiyang, Nguyen Xuan An, Vladislav Lutsenko, and Vladimir Uvarov. "Transient electromagnetic radiation of the lithosphere in a seismically active region." E3S Web of Conferences 127 (2019): 03006. http://dx.doi.org/10.1051/e3sconf/201912703006.

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To study the electromagnetic radiation of the lithosphere associated with seismic waves, we used the recordings of the natural electromagnetic radiation obtained under conditions of weak industrial noise and a high level of microseismicity in the ELF-VLF wave bands. It is shown that these data contain information about the surface waves of the Earth’s crust and are accompanied by a frequency close to the first harmonic of the Schumann resonance. The distribution of spikes over thresholds is obtained, which can be indicators of the activity in the processes of the Earth’s crust. The averaged form of the spikes for different components of the electromagnetic field is obtained. Attention is drawn to the differences in the various components of the electromagnetic field and their diurnal differences are analyzed. The possibility of using the approach to predict the short-term movement of the Earth’s crust is considered.

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47

Ozaki, Mitsunori, Isamu Nagano, Satoshi Yagitani, and Kazutoshi Miyamura. "The Ionospheric Penetration Characteristics of ELF/VLF Waves Radiated from a Dipole Source on the Ground." IEEJ Transactions on Fundamentals and Materials 124, no. 12 (2004): 1239–44. http://dx.doi.org/10.1541/ieejfms.124.1239.

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48

Cohen, M. B., U. S. Inan, D. Piddyachiy, N. G. Lehtinen, and M. Gołkowski. "Magnetospheric injection of ELF/VLF waves with modulated or steered HF heating of the lower ionosphere." Journal of Geophysical Research: Space Physics 116, A6 (June 2011): n/a. http://dx.doi.org/10.1029/2010ja016194.

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49

Chang, Shanshan, Zhengping Zhu, Binbin Ni, Xing Cao, and Weihua Luo. "Resonant scattering of energetic electrons in the outer radiation belt by HAARP-induced ELF/VLF waves." Advances in Space Research 58, no. 7 (October 2016): 1219–28. http://dx.doi.org/10.1016/j.asr.2016.06.018.

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50

Verkhoglyadova, O. P., B. T. Tsurutani, and G. S. Lakhina. "Theoretical analysis of Poynting flux and polarization for ELF-VLF electromagnetic waves in the Earth's magnetosphere." Journal of Geophysical Research: Space Physics 118, no. 12 (December 2013): 7695–702. http://dx.doi.org/10.1002/2013ja019371.

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