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Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals

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A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Upper Atmosphere".

Deadline for manuscript submissions: closed (28 February 2026) | Viewed by 21841

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Special Issue Editors

Prof. Dr. Masashi Hayakawa

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Guest Editor

1. Hayakawa Institute of Seismo Electromagnetics, Co., Ltd. (Hi-SEM), UEC Alliance Center #521, 1-1-1 Kojima-cho, Chofu 182-0026, Tokyo, Japan
2. Advanced Wireless & Communication Research Center (AWCC), The University of Electro-Communications, 1-5-1, Chofugaoka, Chofu 182-8585, Japan
Interests: atmospheric electricity; space physics; ionosphere monitoring; VLF/ELF wave propagation; lithosphere-atmosphere-lithosphere coupling; remote sensing
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Prof. Alexander P. Nickolaenko

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Guest Editor

Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine (Ukraine), Kharkov, Ukraine
Interests: ionosphere; electromagnetic manifestations of earthquakes; schumann resonance; atmospherics; elf radio propagation

Prof. Dr. Xuemin Zhang

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Guest Editor

Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China
Interests: seismo-electromagnetics; electromagnetic satellite; plasma physics; radio wave propagation; seismo-ionospheric physics
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Prof. Dr. Yasuhide Hobara

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Guest Editor

Earth Environment Research Station, Department of Computer Science and Engineering, The University of Electro-Communications (UEC), Tokyo 182-8585, Japan
Interests: total lightning; space plasma; ionospheric perturbations; seismic activity; satellite observation; GLIMS; space weather; wind gust; extreme weather; VLF/ELF; whistler; ionosphere; DEMETER; lightning charge moment
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Special Issue Information

Dear Colleagues,

This Special Issue of Atmosphere aims to gather high-quality original research articles and reviews on the topic of “Understanding space physics and atmospheric electricity with VLF/ELF signals”, with an emphasis on the essential importance of VLF(very low frequency, 3-30kHz)/ELF (extremely low frequency, 1Hz-3kHz) wave phenomena in a wide range of scientific fields from astrophysics, space physics, ionospheric physics, atmospheric electricity, and seismo-electromagnetics.

We would like to invite very active scientists working on VLF/ELF waves to submit their papers (either original or review) to show the readers what kinds of perspectives are going on in different science fields. Astrophysical events such as gamma ray bursts can be monitored with the use of VLF/LF subionospheric propagation date. In space physics, VLF/ELF emissions are one of the most essential aspects in magnetospheric physics, studying wave-particle interactions, and their ionospheric consequence of particle precipitations (Trimpi effects) can be investigated with subionospheric VLF/LF signals. Ionospheric dynamics and perturbations can be monitored only with use of VLF/LF subionospheric signals and ELF/VLF/LF sferics. Next, there are various kinds of wave phenomena associated with atmospheric electricity or atmospheric science. ELF sferics (ELF transients) are the consequence of transient luminous events (TLEs) in the mesosphere suggesting the coupling between the atmosphere and ionosphere. Another Schumann resonance (SR) is the global resonance in the Earth-ionosphere cavity due to the excitation of global lightning activities, so SR can be used effectively to investigate the global lightning activity as well as the lower ionospheric condition. Finaly, a recent subject is the wave phenomena related with earthquakes (EQs); so-called seismo-electromagnetics. In this particular field, there have been observed seismogenic VLF/LF and ELF emissions as a precursor to EQs as an indicator of the lithosphere-atmosphere-ionosphere coupling. Any other papers on VLF/ELF signals are welcome.

The above whole study area is multifaceted and involves several types of measurements (ground- and satellite-based) and analysis methods. For the above reasons, we would like to invite you to submit your recent articles, experimental and theoretical research papers, and case and statistical studies, with respect to the topics described above.

Prof. Dr. Masashi Hayakawa
Prof. Alexander P. Nickolaenko
Prof. Dr. Xuemin Zhang
Prof. Dr. Yasuhide Hobara
Guest Editors

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Keywords

atmospheric electricity
VLF (very-low-frequency, 3–30 kHz)/ELF (extremely low-frequency, 1 Hz–3 kHz) wave
space physics
ionosphere
astrophysics
sesismo-electromagnetics

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Published Papers (12 papers)

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Research

Jump to: Review

15 pages, 2863 KB

Open AccessArticle

Assessing the Potential of Total Lightning for Nowcasting Ground Rainfall in Summer Thunderstorms Using Automatic Density-Dependent Tracking

by Debrupa Mondal, Yasuhide Hobara, Hiroshi Kikuchi and Jeff Lapierre

Atmosphere 2026, 17(4), 364; https://doi.org/10.3390/atmos17040364 - 31 Mar 2026

Viewed by 426

Abstract

The accurate and timely nowcasting of severe weather events such as short-term torrential rainfall is essential for disaster preparedness and early warning systems. Our prior studies have demonstrated a high correlation (0.92) and ~10 min time lag between in-cloud (IC) lightning and ground rainfall. In this study, based on the approach introduced by Shimizu and Uyeda, an automatic method for identifying and tracking convective storm cells, we integrate total lightning data and heavy precipitation data for further improving the prediction accuracy of torrential rainfall. High-resolution 2D weather radar composite precipitation data are collected from XRAIN, operated by MLIT, Japan, and total lightning data (TL, i.e., IC and CG) are collected from the Japanese Total Lightning Network (JTLN). The adapted algorithm is used to track lightning-frequent areas (≥5 and ≥2 pulses per 5 min) as well as heavy (≥50 mm/h) and torrential (≥80 mm/h) precipitation cells. To evaluate the predictive capability of TL, cross-correlation analyses are performed across multiple intensity thresholds and time lags. The results of correlation matrix analysis for identifying the movement of the storm and utilization towards spatiotemporal nowcasting of extreme rainfall is discussed. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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11 pages, 817 KB

Open AccessArticle

Retrieval of Sunrise C-Region Electron Density Using Mid-Range VLF Amplitude and FDTD-Based Optimization

by Taira Shirasaki, Yuki Itabashi and Yoshiaki Ando

Atmosphere 2026, 17(4), 350; https://doi.org/10.3390/atmos17040350 - 31 Mar 2026

Viewed by 308

Abstract

This study presents a method to retrieve the electron density structure of the transient C-region using very-low-frequency (VLF) Earth–ionosphere waveguide propagation. Here, we demonstrate the identification of the C-region from amplitude variations of a mid-range VLF propagation path that is nearly perpendicular to the solar terminator. Previous investigations have primarily relied on phase measurements along long-distance paths with small terminator angles, whereas the present approach utilizes amplitude information under conditions where modal interference is significant. The Faraday International Reference Ionosphere (FIRI-2018) provides an effective semi-empirical model of the lower-ionospheric electron density; however, discrepancies between simulations and observations are often observed at sunrise. To resolve this issue, we introduce Gaussian perturbations to the electron density profile output by FIRI-2018 and optimize their parameters so that finite-difference time-domain (FDTD) simulations reproduce the observed VLF amplitude. The analysis is performed for the 22.2 kHz JJI transmitter signal received in Chofu, Japan over a mid-range propagation path, ∼900 km. The optimized electron density profile successfully reproduces the characteristic features of the C-region, including a temporary enhancement near 65 km altitude during sunrise. These results demonstrate that mid-range VLF amplitude analysis provides a quantitative tool for identifying transient lower- ionospheric structures. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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19 pages, 6128 KB

Open AccessArticle

Ionospheric Schumann Resonance Signal Image Recognition Model and Its Application to the Yangbi Earthquake

by Kexin Zhu, Zhong Li, Jianping Huang, Kexin Pan, Bo Hao and Yuanjing Zhang

Atmosphere 2026, 17(2), 193; https://doi.org/10.3390/atmos17020193 - 12 Feb 2026

Cited by 1 | Viewed by 764

Abstract

The Schumann resonance (SR) signal has attracted much attention as a potential earthquake precursor indicator. To enable rapid identification of these signals from massive volumes of China Seismo-Electromagnetic Satellite (CSES) data, this paper presents a machine learning-based image recognition algorithm. Firstly, the Ultra-Low Frequency (ULF) band power spectrum data of the ionospheric electric field was standardized to enhance the visual contrast of the signal and generate a spectrogram. A small-image dataset with standardized image size and labeled positive and negative samples was constructed by cropping the original images. High-dimensional features of the image were extracted using the deep convolutional neural network VGG16 algorithm, combined with the support vector machine (SVM) algorithm to classify whether the high-dimensional data contains SR signals. The sliding window recognition algorithm is designed to process large-format power spectrum images. The results showed that this VGG16-SVM hybrid model achieved an accuracy of 95.00% on the independent small-image test set, which was superior to both pure SVM and pure VGG16 models. On the large-format image prediction set, the overall accuracy of the model is 81.48%, and the SR physical properties of the recognition signal are verified through frequency statistics. The hybrid model was applied to the SR detection and recognition of the Yangbi earthquake in Yunnan, China, and achieved ideal results. This indicates that the proposed VGG16-SVM hybrid model can quickly and effectively identify SR signals in CSES data, which has important practical value for automated electromagnetic signal analysis in seismic research. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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18 pages, 7385 KB

Open AccessArticle

Observation and Analysis of VLF Electromagnetic Pulse Sequences Triggered by Solar Flares on the CSES

by Siyu Liu, Ying Han, Jianping Huang, Zhong Li, Xuhui Shen and Qingjie Liu

Atmosphere 2026, 17(1), 95; https://doi.org/10.3390/atmos17010095 - 16 Jan 2026

Viewed by 551

Abstract

This study investigates the influence of solar flare events on the time–frequency characteristics of very low frequency (VLF) signals based on observations from the China Seismo–Electromagnetic Satellite (CSES) satellite. By analyzing the VLF electromagnetic wave HDF5 data downloaded on the day of the solar flare, the data were converted into a sequence of spectrograms, and linear structures within them were identified using image processing techniques and the K-means clustering algorithm. In this work, we detect more than twenty candidate transient near-vertical stripe elements (image-domain linear features) in the VLF spectrograms on solar-flare event days and use them as an operational texture fingerprint for large-scale screening. This finding suggests that solar flare events may trigger pulse sequence phenomena in VLF signals, providing new observational evidence for understanding the impact of solar activity on the ionosphere and offering a new perspective for investigating solar-flare effects using VLF signals. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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14 pages, 2937 KB

Open AccessArticle

Guiding Medium Radio Waves in the Magnetosphere: Features and Geophysical Conditions

by Alexey S. Kalishin, Natalia F. Blagoveshchenskaya, Tatiana D. Borisova, Ivan M. Egorov, Gleb A. Zagorskiy and Anna O. Mingaleva

Atmosphere 2025, 16(12), 1350; https://doi.org/10.3390/atmos16121350 - 28 Nov 2025

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Abstract

We present experimental results related to the features and geophysical conditions for the occurrence of the long-delay echo (LDE) signals in the medium-wave (MW) frequency range observed on 20 January 2025, at the Gor’kovskaya observatory near St. Petersburg (60.27° N, 29.38° E). A total of 19 series of experiments on guiding MF in the magnetosphere were carried out, while LDE signals were only registered on January 20, 2025, in evening hours, when the most disturbed conditions were observed (Kp = 4+, ΣKp = 27−). It was found that the LDE signals, with delay times of 310–322 ms, were observed in the evening hours under disturbed magnetic conditions. In such a case, the MW propagates into the magnetosphere to the magnetically conjugate point, is reflected from the topside ionosphere, and returns. The frequency of sounding signal f_SS exceeded the critical frequency of the F2 layer at Gor’kovskaya observatory foF2_GRK but was less than the critical frequency at the magnetic conjugated point foF2_MCP, foF2_GRK < f_SS < foF2_MCP. The LDE signals were observed in the narrow frequency range from 2100 to 2400 kHz. The background geophysical conditions during the occurrence of LDE signals were analyzed using the CADI ionosonde data and Swarm satellite observations. The plausible generation mechanisms for MW guiding in the magnetosphere are discussed. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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20 pages, 3702 KB

Open AccessArticle

Indications of the Impact of the Influence of Large-Scale Atmospheric Disturbances on Quasiperiodic ELF/VLF Emissions Inside the Plasmasphere

by Peter Bespalov, Olga Savina and Polina Shkareva

Atmosphere 2025, 16(11), 1310; https://doi.org/10.3390/atmos16111310 - 20 Nov 2025

Viewed by 512

Abstract

The models of excitation of quasiperiodic ELF/VLF emissions with spectral shape repetition periods from 10 to 300 s are discussed. The primary cause of quasiperiodic (QP) emissions is cyclotron instability of electron radiation belts. Relatively slow processes of cyclotron instability evolution are well described within the framework of the plasma magnetospheric maser (PMM) theory based on the averaged self-consistent system of quasilinear equations for particles and waves. The presence of an eigen-frequency of oscillations of PMM parameters allows explaining many properties of QP 1 emissions, in which not very clear spectral bursts are hiss with resonant modulation mainly near the upper spectral boundary by geomagnetic pulsations of the Pc 3–4 range. The analysis of the general problem of equilibrium of radiation belts shows the possibility of its instability, which is caused by the difference in the pitch-angle dependences of the particle source power and the steady state distribution function. In the nonlinear mode of the specified instability, QP 2 emissions are formed, often with an increase in frequencies in individual spectral bursts. This paper mainly focuses on the study of QP 2 emissions with both a normal and an atypical time structure, as well as with large and fast dynamics of the frequency spectrum. Periodic large-scale atmospheric disturbances with a suitable frequency on the ionosphere can significantly affect the operating modes of the PMM and, as a consequence, the quasiperiodic VLF emissions in the magnetosphere. Infrasonic waves at the altitudes of the E region of the ionosphere can provide excitation of atypical quasiperiodic emissions due to a change in the reflection coefficient of whistler waves from the ionosphere from above. The obtained results are important for interpreting observational data on emissions associated with large-scale processes in the atmosphere. To analyze the magnetosphere response to earthquakes, observation data from the Van Allen Probe spacecraft were used. Also, specific examples of quasiperiodic emissions, probably associated with large-scale atmospheric processes, were obtained during the analysis of observational data. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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13 pages, 3503 KB

Open AccessEditor’s ChoiceArticle

Evaluation of the Quasi-Pre-Seismic Schumann Resonance Signals in the Greek Area During Five Years of Observations (2020–2025)

by Vasilis Tritakis, Ioannis Contopoulos, Janusz Mlynarczyk, Evangelos Chaniadakis and Jerzy Kubisz

Atmosphere 2025, 16(11), 1251; https://doi.org/10.3390/atmos16111251 - 31 Oct 2025

Cited by 1 | Viewed by 2832

Abstract

The Greek territory and the surrounding marine area constitute an excellent laboratory for studying moderate-magnitude earthquakes (4–6 M), as such earthquakes occur very frequently in this region. Ten years ago, it was proposed that there is some kind of relation between earthquakes and unusual Schumann Resonance signals one to twenty days prior to an impending earthquake. During the last five years (2020–2025), a fairly large collection of signals has been gathered that may be considered as precursory seismic signals. Unfortunately, individual case studies overestimate their contribution to the final event and may lead to unjustified ‘extended pictures’ of the phenomenon. In the present article, we systematically attempt to evaluate these signals by examining them as a whole, rather than individually as in case studies. We confirmed that while case studies are a reasonable way to start a research project, they do not guarantee the final result. In our case, while individual studies were very hopeful, the present integrated study led to several unresolved issues that need to be addressed. The results of our work will help to determine whether these signals represent a significant part of the broader LAIC scenario, which is currently the only reliable suggestion for triggering and predicting earthquakes, or whether the origin of these signals should be sought elsewhere. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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15 pages, 2458 KB

Open AccessEditor’s ChoiceArticle

Experimental Study of the Impact of Thunderstorms with Lightning Discharges of Different Polarity on the Ionospheric Parameters

by Valentina Antonova, Vadim Lutsenko and Galina Gordiyenko

Atmosphere 2025, 16(11), 1248; https://doi.org/10.3390/atmos16111248 - 30 Oct 2025

Viewed by 838

Abstract

The study was based on 11 years of measurements of ionospheric parameters and atmospheric electric fields reflecting the polarity of lightning discharges and recording return strokes. The response of ionospheric parameters to thunderstorms with lightning discharges of negative and positive polarity under quiet solar and geomagnetic conditions was considered. No changes in the dynamics of ionospheric parameters are observed during thunderstorms with lightning discharges of negative polarity. Variation in the daily course of total electron content and the appearance of wave-like disturbances with a period of 2–5 h are recorded during thunderstorms with lightning discharges of positive polarity. More small-scale disturbances were also detected. Intensification of the sporadic layer was observed in ~70% of the thunderstorm events with positive lightning discharges. A decrease in the height of the sporadic layer Es (h’Es) by 10 km and an increase in the level of radio wave absorption in the D region of the ionosphere were recorded. The experimental results of the study indicate that the polarity of lightning discharges and electromagnetic effects play a decisive role in the process of thunderstorms affecting the ionosphere. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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20 pages, 6414 KB

Open AccessArticle

D- and F-Region Ionospheric Response to the Severe Geomagnetic Storm of April 2023

by Arnab Sen, Sujay Pal, Bakul Das and Sushanta K. Mondal

Atmosphere 2025, 16(6), 716; https://doi.org/10.3390/atmos16060716 - 13 Jun 2025

Cited by 1 | Viewed by 2050

Abstract

This study investigates the impact on the Earth’s ionosphere of a severe geomagnetic storm (Dst

\sim - 212

nT) that began on 23 April 2023 at around 17:37 UT according to very low-frequency (VLF, 3–30 kHz) or low-frequency (LF, 30–300 [...] Read more.

This study investigates the impact on the Earth’s ionosphere of a severe geomagnetic storm (Dst

\sim - 212

nT) that began on 23 April 2023 at around 17:37 UT according to very low-frequency (VLF, 3–30 kHz) or low-frequency (LF, 30–300 kHz) radio signals and ionosonde data. We analyze VLF/LF signals received by SuperSID monitors located in mid-latitude (Europe) and low-latitude (South America, Colombia) areas across nine different propagation paths in the Northern Hemisphere. Mid-latitude regions exhibited a daytime amplitude perturbation, mostly an increase, by ∼3–5 dB during the storm period, with a subsequent recovery after 7–8 days post April 23. In contrast, signals received in low-latitude regions (UTP, Colombia) did not show significant variation during the storm-disturbed days. We also observe that the 3-hour average of foF2 data declined by up to 3 MHz on April 23 and April 24 at the European Digisonde stations. However, no significant variation in foF2 was observed at the low-latitude Digisonde stations in Brazil. Both the VLF and ionosonde data exhibited anomalies during the storm period in the European regions, confirming that both D- and F-region ionospheric perturbation was caused by the severe geomagnetic storm. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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16 pages, 2985 KB

Open AccessArticle

Impact of Solar Activity on Schumann Resonance: Model and Experiment

by Alexander Pavlovich Nickolaenko, Masashi Hayakawa and Oleksandr Koloskov

Atmosphere 2025, 16(6), 648; https://doi.org/10.3390/atmos16060648 - 27 May 2025

Cited by 2 | Viewed by 8777

Abstract

Using Schumann resonance (SR) records from the Antarctic, we evaluate the impact of the solar activity on the global ionosphere over the period from 2002 to 2024. The updated vertical profile of the middle atmosphere conductivity is applied. The pivoted upper part of profiles above the knee altitude is adjusted to represent different levels of solar activity. The electric (lower) h_C and the magnetic (upper) h_L characteristic heights, the propagation constant ν(f) of the extremely low frequency (ELF) radio waves, and the basic resonance frequency f₁ are computed for the profiles corresponding to the solar maximum, moderate, and minimum activity conditions by using the full-wave solution in the form of the Riccati differential equation. Model data are compared with experimental observations at the Ukrainian Antarctic Station of “Akademik Vernadsky” (geographic coordinates: 65.25° S and 64.25° W). The following results are discussed: (i) Solar activity modifies the upper characteristic height h_L of the ionosphere by ±1 km over the 11-year cycle; (ii) Equations were obtained linking the current level of solar activity with the basic SR frequency, with the magnetic characteristic height, and with the ELF propagation constant; (iii) Based on SR monitoring within two complete solar cycles, a practical rule is proposed: an increase in the index of solar activity I_10.7 by ~150 units raises the first SR frequency by ~0.1 Hz and elevates the magnetic characteristic height by ~2.5 km. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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Review

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40 pages, 3156 KB

Open AccessEditor’s ChoiceReview

A Review of What Can Be Learnt from Tweeks and Related Topics

by Michael J. Rycroft

Atmosphere 2026, 17(2), 152; https://doi.org/10.3390/atmos17020152 - 30 Jan 2026

Viewed by 805

Abstract

Tweeks are ELF/VLF radio signals originating from lightning discharges that exhibit dispersion due to their propagation in the Earth-ionosphere waveguide. Examples of the waveforms of tweeks and their dynamic frequency-time spectra are presented and interpreted. Tweeks observed in the daytime and night-time are compared and contrasted. Tweeks observed during a solar eclipse are also discussed, as are those due to volcanic lightning and those claimed to be recorded some hours or days before a strong earthquake. The variations of tweek occurrence with season and geomagnetic activity, and with variations of solar radiation over the 11-year solar cycle, are reviewed. Wherever possible, geophysical interpretations are discussed. Theoretical models of tweek waveforms and spectra are considered; they vary according to the lightning current model used, the distance from the source (≥1 Mm), the vertical profile of ionospheric D-region ionisation and the specific mode theory used. The simplest interpretation shows that the first-order tweek cut- off frequency ~1.8 kHz is explained as reflection by the ionosphere at a height of ~83 km where the electron density is ~27 × 10⁶ m⁻³. More complex interpretations are also reviewed and compared with electron density observations made by rockets and with profiles given by lower ionospheric models such as the International Reference Ionosphere or the Faraday International Reference Ionosphere. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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40 pages, 7970 KB

Open AccessReview

Review of Subionospheric VLF/LF Radio Signals for the Study of Seismogenic Lower-Ionospheric Perturbations

by Masashi Hayakawa

Atmosphere 2025, 16(11), 1312; https://doi.org/10.3390/atmos16111312 - 20 Nov 2025

Cited by 2 | Viewed by 2139

Abstract

It has recently been recognized that the ionosphere is highly sensitive to pre-seismic effects, and the detection of ionospheric perturbations associated with earthquakes (EQs) is one of the most promising candidates for short-term EQ prediction. In this review, we focus on a possible use of VLF/LF (very low frequency (3–30 kHz)/low frequency (30–300 kHz)) radio sounding of seismo-ionospheric perturbations to study seismogenic effects. Because an understanding of the early history in any area will provide a lot of crucial insights to the readers (especially to young scientists) working in the field of seismo-electromagnetics, we provide a brief history (mainly results reported by a Russian group of scientists) of the initial application of subionospheric VLF/LF propagation for the study of ionospheric perturbations associated with EQs, and then we present our first convincing evidence on the ionospheric perturbation for the disastrous Kobe EQ in 1995, with a new analysis method based on the shifts in terminator times in VLF/LF diurnal variations (minima in the diurnal variations in amplitude and phase). We then summarize our latest results on further evidence of seismo-ionospheric perturbations. Firstly, we present a few statistical studies on the correlation between VLF/LF propagation anomalies and EQs based on long-term data. Secondly, we showcase studies for a few large, recent EQs (including the 2011 Tohoku EQ). Building on those EQ precursor studies, we demonstrate scientific topics and the underlying physics that can be studied using VLF/LF data, highlighting recent achievements including the revolutionary perspective of lithosphere–atmosphere–ionosphere coupling (LAIC) (or how the ionosphere is perturbed due to the lithospheric pre-EQ activity), modulation in VLF/LF data by atmospheric gravity waves (AGWs), Doppler-shift observation, satellite observation of VLF/LF transmitter signals, etc., together with the recommendation of the application of new technologies such as artificial intelligence and critical analysis to VLF/LF analysis. Finally, we want to emphasize again the essential significance of the information on lower-ionospheric perturbations within LAIC studies. Full article

(This article belongs to the Special Issue Understanding Space Physics and Atmospheric Electricity with VLF/ELF Signals)

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