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Biswas, Sagardweep, Subrata Kundu, Sudipta Sasmal, Dimitrios Z. Politisb, Stelios M. Potirakis i Masashi Hayakawa. "Preseismic Perturbations and their Inhomogeneity as Computed from Ground- and Space-Based Investigation during the 2016 Fukushima Earthquake". Journal of Sensors 2023 (24.02.2023): 1–23. http://dx.doi.org/10.1155/2023/7159204.
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We present the atmospheric anomalies instigated through seismogenic sources by a multichannel observation using ground- and satellite-based systems. This study emphasizes the seismic event which happened on the east coast of Japan, near the Fukushima Prefecture on November 21, 2016 (in UTC), with a magnitude of 6.9 and a depth of 11.4 km. We mainly focus on the atmospheric and ionospheric irregularities via acoustic and electromagnetic channels originating from earthquakes in the process of the lithosphere, atmosphere, and ionospheric coupling (LAIC) mechanism. In the acoustic channel, we study the seismogenic atmospheric gravity wave (AGW) which perturbs the local lower atmosphere. The observation of nighttime fluctuations in the very low frequency (VLF) signals and total electron content (TEC) is used to investigate the atmospheric perturbation through the electromagnetic channel. For the ground-based observations, a VLF signal network consisting of 5 receivers in Japan is used to study by recording the VLF amplitude transmitted from the Japanese transmitter JJI (22.2 kHz). VLF nighttime fluctuation is used to check the unusualities due to the earthquake. Preseismic wavelike structures having periods of AGW are observed in the nighttime signal. Direct investigation of such AGWs is done by computing the potential energy related to AGW from the sounding of the atmosphere using broadband emission radiometry (SABER) temperature profiles mounted on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. Ionospheric TEC inspection is done by using a ground-based global navigation satellite system (GNSS) receiver from the International GNSS Survey (IGS) station MIZU in Japan and observing anomalies in diurnal TEC around 6 and 10 days prior to the earthquake. We also obtain the wavelike structure of AGW from the small-scale fluctuation of TEC using wavelet analysis. All the parameters are found to be preseismic for this earthquake; the acoustics channel gives more consistent outcomes than the electromagnetic channel.
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Kachakhidze, M. K., Z. A. Kereselidze i N. K. Kachakhidze. "The model of own seismoelectromagnetic oscillations of LAI system". Solid Earth Discussions 2, nr 2 (26.07.2010): 233–50. http://dx.doi.org/10.5194/sed-2-233-2010.
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Abstract. Very low frequency (VLF) electromagnetic radiation (in diapason 1 kHz – 1 MHz) in atmosphere, generated during earthquake preparation period, may be connected with linear size, characterizing incoming earthquake source. In order to argue this hypothesis very simple quasi-electrostatic model is used: local VLF radiation may be the manifestation of own electromagnetic oscillations of concrete seismoactive segments of lithosphere-atmosphere system. This model explains qualitatively well-known precursor effects of earthquakes. At the same time, it will be principally possible to forecast expected earthquake with certain precision if we use this model after diagnosing existed data. As physical basis of working hypothesis is atmospheric effect of polarization charges occurred in surface layer of the Earth, it is possible to test the below constructed model in medium, where reasons of polarization charge generation may be different from piezoelectric mechanism, for example, due to electrolytic hydration.
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Kachakhidze, M. K., Z. A. Kereselidze i N. K. Kachakhidze. "The model of self-generated seismo-electromagnetic oscillations of the LAI system". Solid Earth 2, nr 1 (8.02.2011): 17–23. http://dx.doi.org/10.5194/se-2-17-2011.
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Abstract. Very low frequency (VLF) electromagnetic radiation (in diapason 1 kHz–1 MHz) in the atmosphere, generated during an earthquake preparation period, may be connected with the linear size characterising the expected earthquake focus. In order to argue this hypothesis, a very simple quasi-electrostatic model is used: the local VLF radiation may represent the self-generated (own) electromagnetic oscillations of interactive seismoactive segments of the lithosphere-atmosphere system. This model qualitatively explains the well-known precursor effects of earthquakes. In addition, using this model after diagnosing existing data makes it principally possible to forecast an expected earthquake with certain precision. As a physical basis of the working hypothesis is the atmospheric effect of polarization charges occurring in the surface layer of the Earth, it is possible to test the following constructed model in the Earth's crust, where the reason for polarization charge generation may be different from piezo-electric mechanism, e.g., some other mechanism.
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Buchanan, Weston P., Maxim de Jong, Rachana Agrawal, Janusz J. Petkowski, Archit Arora, Sarag J. Saikia, Sara Seager i James Longuski. "Aerial Platform Design Options for a Life-Finding Mission at Venus". Aerospace 9, nr 7 (7.07.2022): 363. http://dx.doi.org/10.3390/aerospace9070363.
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Mounting evidence of chemical disequilibria in the Venusian atmosphere has heightened interest in the search for life within the planet’s cloud decks. Balloon systems are currently considered to be the superior class of aerial platform for extended atmospheric sampling within the clouds, providing the highest ratio of science return to risk. Balloon-based aerial platform designs depend heavily on payload mass and target altitudes. We present options for constant- and variable-altitude balloon systems designed to carry out science operations inside the Venusian cloud decks. The Venus Life Finder (VLF) mission study proposes a series of missions that require extended in situ analysis of Venus cloud material. We provide an overview of a representative mission architecture, as well as gondola designs to accommodate a VLF instrument suite. Current architecture asserts a launch date of 30 July 2026, which would place an orbiter and entry vehicle at Venus as early as November 29 of that same year.
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Zhao, Shufan, Xuhui Shen, Weiyan Pan, Xuemin Zhang i Li Liao. "Penetration characteristics of VLF wave from atmosphere into lower ionosphere". Earthquake Science 23, nr 3 (czerwiec 2010): 275–81. http://dx.doi.org/10.1007/s11589-010-0723-9.
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Rodger, C. J., M. A. Clilverd, N. R. Thomson, D. Nunn i J. Lichtenberger. "Lightning driven inner radiation belt energy deposition into the atmosphere: regional and global estimates". Annales Geophysicae 23, nr 11 (21.12.2005): 3419–30. http://dx.doi.org/10.5194/angeo-23-3419-2005.
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Abstract. In this study we examine energetic electron precipitation fluxes driven by lightning, in order to determine the global distribution of energy deposited into the middle atmosphere. Previous studies using lightning-driven precipitation burst rates have estimated losses from the inner radiation belts. In order to confirm the reliability of those rates and the validity of the conclusions drawn from those studies, we have analyzed New Zealand data to test our global understanding of troposphere to magnetosphere coupling. We examine about 10000h of AbsPAL recordings made from 17 April 2003 through to 26 June 2004, and analyze subionospheric very-low frequency (VLF) perturbations observed on transmissions from VLF transmitters in Hawaii (NPM) and western Australia (NWC). These observations are compared with those previously reported from the Antarctic Peninsula. The perturbation rates observed in the New Zealand data are consistent with those predicted from the global distribution of the lightning sources, once the different experimental configurations are taken into account. Using lightning current distributions rather than VLF perturbation observations we revise previous estimates of typical precipitation bursts at L~2.3 to a mean precipitation energy flux of ~1×10-3 ergs cm-2s-1. The precipitation of energetic electrons by these bursts in the range L=1.9-3.5 will lead to a mean rate of energy deposited into the atmosphere of 3×10-4 ergs cm-2min-1, spatially varying from a low of zero above some ocean regions to highs of ~3-6×10-3 ergs cm-2min-1 above North America and its conjugate region.
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Zhao, Shufan, Xuhui Sheng, Weiyan Pan i Xuemin Zhang. "Penetration characteristics of VLF wave from atmosphere into the lower ionosphere". Chinese Journal of Space Science 31, nr 2 (2011): 194. http://dx.doi.org/10.11728/cjss2011.02.194.
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Srećković, Vladimir A., Desanka M. Šulić, Ljubinko Ignjatović i Veljko Vujčić. "Low Ionosphere under Influence of Strong Solar Radiation: Diagnostics and Modeling". Applied Sciences 11, nr 16 (4.08.2021): 7194. http://dx.doi.org/10.3390/app11167194.
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Solar flares (SFs) and intense radiation can generate additional ionization in the Earth’s atmosphere and affect its structure. These types of solar radiation and activity create sudden ionospheric disturbances (SIDs), affect electronic equipment on the ground along with signals from space, and potentially induce various natural disasters. Focus of this work is on the study of SIDs induced by X-ray SFs using very low frequency (VLF) radio signals in order to predict the impact of SFs on Earth and analyze ionosphere plasmas and its parameters. All data are recorded by VLF BEL stations and the model computation is used to obtain the daytime atmosphere parameters induced by this extreme radiation. The obtained ionospheric parameters are compared with results of other authors. For the first time we analyzed physics of the D-region—during consecutive huge SFs which continuously perturbed this layer for a few hours—in detail. We have developed an empirical model of the D-region plasma density and gave a simple approximative formula for electron density.
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Silber, Israel, Colin Price i Craig J. Rodger. "Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers". Atmospheric Chemistry and Physics 16, nr 5 (14.03.2016): 3279–88. http://dx.doi.org/10.5194/acp-16-3279-2016.
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Abstract. Earth's middle and upper atmosphere exhibits several dominant large-scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere–lower thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequency (VLF) narrowband (NB) subionospheric measurements. As VLF signals are reflected off the ionospheric D region (at altitudes of ∼ 65 and ∼ 85 km, during the day and night, respectively), this implies that the upper part of the D region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D region is NOx molecule transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D region in general and VLF wave propagation in particular.
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Silber, I., C. G. Price i C. J. Rodger. "Semi-annual oscillation (SAO) of the nighttime ionospheric D-region as detected through ground-based VLF receivers". Atmospheric Chemistry and Physics Discussions 15, nr 21 (4.11.2015): 30383–407. http://dx.doi.org/10.5194/acpd-15-30383-2015.
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Abstract. Earth's middle and upper atmosphere exhibits several dominant large scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere-lower-thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequencies (VLF) narrow-band subionospheric measurements. As VLF signals are reflected off the ionospheric D-region (at altitudes of ~65 and ~85 km, during the day and night, respectively), this implies that the upper part of the D-region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D-region is due to NOx molecules transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D-region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D-region in general and VLF wave propagation in particular.
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Sheldon, W. R., J. R. Benbrook i E. A. Bering. "Rocket investigations of electron precipitation and VLF waves in the Antarctic upper atmosphere". Reviews of Geophysics 26, nr 3 (1988): 519. http://dx.doi.org/10.1029/rg026i003p00519.
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Koshevaya, S., N. Makarets, V. Grimalsky, A. Kotsarenko i R. Perez Enríquez. "Spectrum of the seismic-electromagnetic and acoustic waves caused by seismic and volcano activity". Natural Hazards and Earth System Sciences 5, nr 2 (2.02.2005): 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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Kachakhidze, M. K., Z. A. Kereselidze, N. K. Kachakhidze, G. T. Ramishvili i V. J. Kukhianidze. "In connection with identification of VLF emissions before L'Aquila earthquake". Natural Hazards and Earth System Sciences 12, nr 4 (16.04.2012): 1009–15. http://dx.doi.org/10.5194/nhess-12-1009-2012.
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Abstract. The present paper deals with an attempt to check the theoretical model of self-generated seismo-electromagnetic oscillations of LAI system on the basis of retrospective data. Application of the offered simple model enables one to explain qualitatively the mechanism of VLF electromagnetic emission initiated in the process of an earthquake preparation. Besides, the model enables us to associate telluric character geoelectric and geomagnetic perturbations incited by rock polarization and self-generated electromagnetic oscillations of lithosphere-atmosphere system. L'Aquila earthquake taken as an example to isolate reliably the Earth VLF emission from the magnetospheric electromagnetic emission of the same frequency range, MHD criterion is offered together with geomagnetic activity indexes. On the basis of the considered three earthquakes, according to the opinion of authors the model of self-generated seismo-electromagnetic oscillations of the LAI system will enable us to approach the problem of resolution of earthquake prediction with certain accuracy.
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Hayakawa, Masashi, Alexander Schekotov, Jun Izutsu, Shih-Sian Yang, Maria Solovieva i Yasuhide Hobara. "Multi-Parameter Observations of Seismogenic Phenomena Related to the Tokyo Earthquake (M = 5.9) on 7 October 2021". Geosciences 12, nr 7 (30.06.2022): 265. http://dx.doi.org/10.3390/geosciences12070265.
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Multi-parameter observations, powerful for the study of lithosphere–atmosphere–ionosphere coupling (LAIC), have been performed for a recent Tokyo earthquake (EQ) with a moderate magnitude (M = 5.9) and rather larger depth (~70 km) on 7 October 2021, in the hope of predicting the next Kanto (Tokyo) huge EQ, such as the 1923 Great Kanto EQ (with a magnitude greater than 7). Various possible precursors have been searched during the two-month period of 1 September to 31 October 2021, based on different kinds of data sets: (i) ULF (ultra-low frequency) magnetic data from Kakioka, Japan, (ii) ULF/ELF (extremely low frequency) magnetic field data from the Chubu University network, (iii) meteorological data (temperature and humidity) from the Japan Meteorological Agency (JMA), (iv) AGW (atmospheric gravity wave) ERA5 data provided by the European Centre for Medium-Range Weather Forecast (ECMWF), (v) subionospheric VLF/LF (very low frequency/low frequency) data from Russia and Japan, (vi) ionosonde Japanese data, and (vii) GIM (global ionosphere map) TEC (total electron content) data. After extensive analyses of all of the above data, we have found that there are a few obvious precursors: (i) ULF/ELF electromagnetic radiation in the atmosphere, and (ii) lower ionospheric perturbations (with two independent tools from the ULF depression and subionospheric VLF anomaly) which took place just two days before the EQ. Further, ULF/ELF atmospheric electromagnetic radiation has been observed from approximately one week before the EQ until a few days after the EQ, which seems to be approximately synchronous in time to the anomalous variation in meteorological parameters (a combination of temperature and humidity, atmospheric chemical potential). On the other hand, there have been no clear anomalies detected in the stratospheric AGW activity, and in the NmF2 and TEC data for the upper F region ionosphere. So, it seems that the lithospheric origin is not strong enough to perturb the upper F region. Finally, we discuss the possible hypothesis for the LAIC process, and we can conclude that the AGW hypothesis might be ruled out, but other possible channels such as the chemical channel (radon emanation) and the associated effects might be in operation, at least, for this Tokyo EQ.
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КОРСАКОВ, А. А., i Н. А. СОКРУТ. "Amplitude variations of VLF radio signals of JXN and DHO transmitters received in Yakutsk during the solar eclipse June 10, 2021". Vestnik of North-Eastern Federal University, nr 1 (6.04.2023): 29–41. http://dx.doi.org/10.25587/svfu.2023.58.22.003.
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Аннотация. Солнечное затмение оказывает влияние на верхнюю атмосферу Земли. Преимуществом такого естественного воздействия является то, что время затмения можно рассчитать заранее и подготовиться к экспериментам. Динамические процессы во время каждого затмения зависят от гелиогеофизической обстановки. Радиоволны диапазона ОНЧ способны распространяться на тысячи километров в волноводе Земля – ионосфера. Расположение ОНЧ радиотрасс определяет пространство для мониторинга нижней ионосферы (как части верхней атмосферы). Исследовались вариации амплитуд ОНЧ радиосигналов, принимаемых в Якутске от передатчиков DHO (23,4 кГц, 53,08° N, 7,62° E) и JXN (16,4 кГц, 66,97° N, 13,87° E). Большая часть этих радиотрасс располагается на арктической территории Евразии. Зарегистрированные суточные вариации амплитуды ОНЧ сигналов DHO и JXN с 7 по 13 июня 2021 г. объясняются вариацией потока ионизирующего излучения солнца, интерференцией мод высших порядков при прохождении восходного и заходного терминаторов по участкам радиотрасс, а также режимом работы передатчиков. В период солнечного затмения 10 июня 2021 г. минимальное среднее значение отношения площадей открытой части диска Солнца к полной составило 0,532 (11:39:18 UTC) и 0,411 (11:33:00 UTC) вдоль радиотрасс DHO – Якутск и JXN – Якутск соответственно. Эффект затмения проявился в виде повышения амплитуды в максимуме на 1,62 дБ (11:39:18 UTC) и 1,4 дБ (11:26:42 UTC) для сигналов DHO и JXN соответственно. Малые затраты на изготовление ОНЧ приемников, возможность охвата больших территорий делают регистрацию ОНЧ сигналов удобным инструментом для зондирования нижней ионосферы над труднодоступными и малонаселенными территориями. Abstract. A solar eclipse affects the Earth's upper atmosphere. The eclipse time can be calculated in advance, which allows us to prepare for experiments. Dynamic processes during each specific eclipse depend on the heliogeophysical environment. VLF radio waves can propagate thousands of kilometers in the Earth-ionosphere waveguide. The location of the VLF radio paths determines the space for monitoring the lower ionosphere (as a part of the upper atmosphere). We applied a method of studying the amplitude variation of VLF radio signals from DHO (23.4 kHz, 53.08° N, 7.62° E) and JXN (16.4 kHz, 66.97° N, 13.87° E) transmitters received in Yakutsk. The most part of these radio paths is located along the Arctic territory of Eurasia. The diurnal VLF amplitude variations of the DHO и JXN signals from June 7 to 13 are explained by the solar ionizing flux variation, the higher-order modes interference during the passage of the rising and setting terminators along the elements of the radio paths, and the transmitters operating mode. During the solar eclipse of June 10, 2021, the minimum average ratio value of the open part of the solar disk area to the full disk area was 0.532 (11:39:18 UTC) and 0.411 (11:33:00 UTC) along the DHO – Yakutsk and JXN – Yakutsk radio paths, respectively. The eclipse effect appeared as an amplitude increase at the maximum of 1.62 dB (11:39:18 UTC) and 1.4 dB (11:26:42 UTC) for the DHO and JXN signals, respectively. Furthermore, our data provide the low VLF receivers manufacturing costs and the ability to cover large areas make the VLF registration a convenient tool for sounding the lower ionosphere over the hard-to-reach and sparsely populated areas.
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Neal, Jason J., Craig J. Rodger, Mark A. Clilverd, Neil R. Thomson, Tero Raita i Thomas Ulich. "Long-term determination of energetic electron precipitation into the atmosphere from AARDDVARK subionospheric VLF observations". Journal of Geophysical Research: Space Physics 120, nr 3 (marzec 2015): 2194–211. http://dx.doi.org/10.1002/2014ja020689.
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Muto, F., M. Yoshida, T. Horie, M. Hayakawa, M. Parrot i O. A. Molchanov. "Detection of ionospheric perturbations associated with Japanese earthquakes on the basis of reception of LF transmitter signals on the satellite DEMETER". Natural Hazards and Earth System Sciences 8, nr 1 (26.02.2008): 135–41. http://dx.doi.org/10.5194/nhess-8-135-2008.
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Abstract. There have been recently reported a lot of electromagnetic phenomena associated with earthquakes (EQs). Among these, the ground-based reception of subionospheric waves from VLF/LF transmitters, is recognized as a promising tool to investigate the ionospheric perturbations associated with EQs. This paper deals with the corresponding whistler-mode signals in the upper ionosphere from those VLF/LF transmitters, which is the counterpart of subionospheric signals. The whistler-mode VLF/LF transmitter signals are detected on board the French satellite, DEMETER launched on 29 June 2004. We have chosen several large Japanese EQs including the Miyagi-oki EQ (16 August 2005; M=7.2, depth=36 km), and the target transmitter is a Japanese LF transmitter (JJY) whose transmitter frequency is 40 kHz. Due to large longitudinal separation of each satellite orbit (2500 km), we have to adopt a statistical analysis over a rather long period (such as 3 weeks or one month) to have reliable data set. By analyzing the spatial distribution of JJY signal intensity (in the form of signal to noise ratio SNR) during a period of 4 months including the Miyagi-oki EQ, we have found significant changes in the intensity; generally the SNR is significantly depleted before the EQ, which is considered to be a precursory ionospheric signature of the EQ. This abnormal effect is reasonably explained in terms of either (1) enhanced absorption of whistler-mode LF signals in the lower ionosphere due to the lowering of the lower ionosphere, or (2) nonlinear wave-wave scattering. Finally, this analysis suggests an important role of satellite observation in the study of lithosphere-atmosphere-ionosphere coupling.
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De, S. S., B. K. De, B. Bandyopadhyay, S. Paul, D. K. Haldar, A. Bhowmick, S. Barui i R. Ali. "Effects on atmospherics at 6 kHz and 9 kHz recorded at Tripura during the India-Pakistan Border earthquake". Natural Hazards and Earth System Sciences 10, nr 4 (16.04.2010): 843–55. http://dx.doi.org/10.5194/nhess-10-843-2010.
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Abstract. The outcome of the results of some analyses of electromagnetic emissions recorded by VLF receivers at 6 kHz and 9 kHz over Agartala, Tripura, the North-Eastern state of India (Lat. 23° N, Long. 91.4° E) during the large earthquake at Muzaffarabad (Lat. 34.53° N, Long. 73.58° E) at Kashmir under Pakistan have been presented here. Spiky variations in integrated field intensity of atmospherics (IFIA) at 6 and 9 kHz have been observed 10 days prior (from midnight of 28 September 2005) to the day of occurrence of the earthquake on 8 October 2005 and the effect continued, decayed gradually and eventually ceased on 16 October 2005. The spikes distinctly superimposed on the ambient level with mutual separation of 2–5 min. Occurrence number of spikes per hour and total duration of their occurrence have been found remarkably high on the day of occurrence of the earthquake. The spike heights are higher at 6 kHz than at 9 kHz. The results have been explained on the basis of generation of electromagnetic radiation associated with fracture of rocks, their subsequent penetration into the Earth's atmosphere and finally their propagation between Earth-ionosphere waveguide. The present observation shows that VLF anomaly is well-confined between 6 and 9 kHz.
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Miś, Tomasz Aleksander, i Józef Modelski. "Electrical Phenomena on Fully Airborne Vertical Electric Antennas in Extreme Weather Conditions". Energies 16, nr 1 (21.12.2022): 52. http://dx.doi.org/10.3390/en16010052.
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This is a conference extension of the paper ‘Investigation on the mature storm cloud’s electric field using long airborne antennas’. The use of vertical antennas (including the VEDs—Vertical Electric Dipoles), lifted up by aerostats to high altitudes without being anchored to the ground, presents numerous advantages in comparison with large terrestrial VLF (Very Low Frequency) antenna structures. A slow-moving floating-earth conductor—a vertical wire antenna—is subjected to intense electrification mechanisms in the atmosphere and inside the cloud layers, producing additional risks for the transmitter and the flight train itself. The electrical potential achieved in this process is, therefore, compared with the flashover voltages over the antenna’s upper fixing point, defining the voltage margins at which the VLF transmitter is able to operate. The electrification processes are also compared to the model based on experimental data on the occurrence of corona discharges over a long, vertical wire traversing a storm cloud layer. The external electric field strength (around the antenna wire) is calculated and compared with older experimental data for storm clouds for various locations, showing the correctness of the proposed analytical electrification model, and, therefore, expanding it with the loss of the electric charge via corona.
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Yin, Weike, Bing Wei i Shitian Zhang. "Full-wave method for the analysis of the radiation characteristics of a VLF source in the atmosphere". Results in Physics 15 (grudzień 2019): 102682. http://dx.doi.org/10.1016/j.rinp.2019.102682.
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Molchanov, O. A., i M. Hayakawa. "VLF monitorig of atmosphere-ionosphere boundary as a tool to study planetary waves evolution and seismic influence". Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science 26, nr 6 (styczeń 2001): 453–58. http://dx.doi.org/10.1016/s1464-1917(01)00030-7.
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Firstov, Pavel P., Evgeniy I. Malkin, Rinat R. Akbashev, Gennadiy I. Druzhin, Nina V. Cherneva, Robert H. Holzworth, Vladimir N. Uvarov i Ivan E. Stasiy. "Registration of Atmospheric-Electric Effects from Volcanic Clouds on the Kamchatka Peninsula (Russia)". Atmosphere 11, nr 6 (15.06.2020): 634. http://dx.doi.org/10.3390/atmos11060634.
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The paper is devoted to the description of observations over atmospheric and electric effects from volcanic eruptions on Kamchatka peninsula (Russia) and perspectives of their development. To collect information about atmospheric-electric effects accompanying the eruptions of Kamchatka volcanoes, three sensor networks and a VLF radio direction finding station are used. The World Wide Lightning Location Network (WWLLN) provides information on high-current lightning discharges that occur during the development of an eruptive cloud (EC). Variations in the electric field of the atmosphere (AEF E z ), during the passage of EC, were obtained by a network of electric field mills at the sites for volcanic activity observations. Seismic detector network was used to make precision reference to the eruptions. Based on the data obtained, a description is given of the dynamics of eruptions of the most active volcanoes in Kamchatka and the Northern Kuril Islands (Shiveluch, Bezymianny, Ebeko). The paper presents a simulation of the response of the atmospheric electric field, which showed that the approximation by the field of distributed charges makes it possible to estimate the volume charges of EC. The fact of a multi-stage volcanic thunderstorm is confirmed. The first stage is associated with the formation of an eruptive column, and the second with the emergence, development and transfer of EC. Registration of electrical and electromagnetic processes in eruptive clouds can be one of the components of complex observations of volcanic eruptions in order to assess the ash hazard for air transport.
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Roldugin, V. C., M. I. Beloglazov i G. F. Remenets. "Total ozone decrease in the Arctic after REP events". Annales Geophysicae 18, nr 3 (31.03.2000): 332–36. http://dx.doi.org/10.1007/s00585-000-0332-3.
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Abstract. Eight periods of relativistic electron precipitation (REP) with electron energies of more than 300 keV are identified from VLF data (10-14 kHz) monitored along the Aldra (Norway) - Apatity (Kola peninsula) radio trace. In these cases, anomalous ionization below 55-50 km occurred without disturbing the higher layers of the ionosphere. The daily total ozone values in Murmansk for six days before and six days after the REP events are compared. In seven of eight events a decrease in the total ozone of about 20 DU is observed. In one event of 25 March, 1986, the mean total ozone value for six days before the REP is bigger than that for six days after, but this a case of an extremely high ozone increase (144 DU during the six days). However, on days 3 and 4 there was a minimum of about 47 DU with regard to REP days, so this case also confirms the concept of the ozone decrease after REP. The difference between mean ozone values for periods six days before and six days after the REPs was found also for 23 points in Arctic on TOMS data. The difference was negative only in Murmansk longitudinal sector. Along the meridian of the trace it was negative at high latitudes in both hemispheres and was near zero at low latitudes.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry) - Meteorology and atmospheric dynamics (polar meteorology)
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Баишев, Дмитрий, Dmitry Baishev, Сергей Самсонов, Sergey Samsonov, Алексей Моисеев, Aleksey Moiseev, Роман Бороев i in. "Monitoring and investigating space weather effects with meridional chain of instruments in Yakutia: a brief overview". Solar-Terrestrial Physics 3, nr 2 (9.08.2017): 25–33. http://dx.doi.org/10.12737/stp-3220175.
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The Yakutsk Meridional Chain (YMC) of IKFIA SB RAS, located along the 190° magnetic meridian, is equipped with geophysical and radiophysical instruments for monitoring space weather in northeast-ern Russia. YMC includes four basic stations in Yakutsk, Tixie, Zhigansk, and Maymaga, and six additional observation sites in Neryungri, Zyryanka, Kystatyam, Dzhardzhan, Chokurdakh, and Kotelny Island. It provides continuous monitoring of near-Earth space in order to obtain data on magnetic field variations, cosmic radio noise, VLF radiation, and ionospheric parameters in the complex upper atmosphere – ionosphere –magnetosphere system. In addition, long-term experimental research into space weather effects on human health is conducted at Tixie and Yakutsk. The report describes the meridional chain of instruments at subauroral and auroral latitudes and gives a brief overview of scientific results of monitoring and investigation into space weather effects in Yakutia. It also observes participation of IKFIA SB RAS in international projects (Intermagnet, MAGDAS, GIRO).
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Баишев, Дмитрий, Dmitry Baishev, Сергей Самсонов, Sergey Samsonov, Алексей Моисеев, Aleksey Moiseev, Роман Бороев i in. "Monitoring and investigating space weather effects with meridional chain of instruments in Yakutia: a brief overview". Solnechno-Zemnaya Fizika 3, nr 2 (29.06.2017): 27–35. http://dx.doi.org/10.12737/22607.
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The Yakutsk Meridional Chain (YMC) of IKFIA SB RAS, located along the 190° magnetic meridian, is equipped with geophysical and radiophysical instruments for monitoring space weather in northeast-ern Russia. YMC includes four basic stations in Yakutsk, Tixie, Zhigansk, and Maymaga, and six additional observation sites in Neryungri, Zyryanka, Kystatyam, Dzhardzhan, Chokurdakh, and Kotelny Island. It provides continuous monitoring of near-Earth space in order to obtain data on magnetic field variations, cosmic radio noise, VLF radiation, and ionospheric parameters in the complex upper atmosphere – ionosphere –magnetosphere system. In addition, long-term experimental research into space weather effects on human health is conducted at Tixie and Yakutsk. The report describes the meridional chain of instruments at subauroral and auroral latitudes and gives a brief overview of scientific results of monitoring and investigation into space weather effects in Yakutia. It also observes participation of IKFIA SB RAS in international projects (Intermagnet, MAGDAS, GIRO).
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Hayakawa, Masashi, Jun Izutsu, Alexander Schekotov, Shih-Sian Yang, Maria Solovieva i Ekaterina Budilova. "Lithosphere–Atmosphere–Ionosphere Coupling Effects Based on Multiparameter Precursor Observations for February–March 2021 Earthquakes (M~7) in the Offshore of Tohoku Area of Japan". Geosciences 11, nr 11 (22.11.2021): 481. http://dx.doi.org/10.3390/geosciences11110481.
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The purpose of this paper is to discuss the lithosphere–atmosphere–ionosphere coupling (LAIC) effects with the use of multiparameter precursor observations for two successive Japanese earthquakes (EQs) (with a magnitude of around 7) in February and March 2021, respectively, considering a seemingly significant difference in seismological and geological hypocenter conditions for those EQs. The second March EQ is very similar to the famous 2011 Tohoku EQ in the sense that those EQs took place at the seabed of the subducting plate, while the first February EQ happened within the subducting plate, not at the seabed. Multiparameter observation is a powerful tool for the study of the LAIC process, and we studied the following observables over a 3-month period (January to March): (i) ULF data (lithospheric radiation and ULF depression phenomenon); (ii) ULF/ELF atmospheric electromagnetic radiation; (iii) atmospheric gravity wave (AGW) activity in the stratosphere, extracted from satellite temperature data; (iv) subionospheric VLF/LF propagation data; and (v) GPS TECs (total electron contents). In contrast to our initial expectation of different responses of anomalies to the two EQs, we found no such conspicuous differences of electromagnetic anomalies between the two EQs, but showed quite similar anomaly responses for the two EQs. It is definite that atmospheric ULF/ELF radiation and ULF depression as lower ionospheric perturbation are most likely signatures of precursors to both EQs, and most importantly, all electromagnetic anomalies are concentrated in the period of about 1 week–9 days before the EQ to the EQ day. There seems to exist a chain of LAIC process (cause-and-effect relationship) for the first EQ, while all of the observed anomalies seem to occur nearly synchronously in time for the send EQ. Even though we tried to discuss possible LAIC channels, we cannot come to any definite conclusion about which coupling channel is plausible for each EQ.
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Remenets, G. F., i V. A. Shishaev. "VLF wave propagation and middle polar atmosphere as a detector of ultra-energetic relativistic electron precipitations in 1988–1992 years". Journal of Atmospheric and Solar-Terrestrial Physics 196 (grudzień 2019): 105145. http://dx.doi.org/10.1016/j.jastp.2019.105145.
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Weber, Robert E., Janusz J. Petkowski i Monika U. Weber. "Direct In-Situ Capture, Separation and Visualization of Biological Particles with Fluid-Screen in the Context of Venus Life Finder Mission Concept Study". Aerospace 9, nr 11 (6.11.2022): 692. http://dx.doi.org/10.3390/aerospace9110692.
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Evidence of chemical disequilibria and other anomalous observations in the Venusian atmosphere motivate the search for life within the planet’s temperate clouds. To find signs of a Venusian aerial biosphere, a dedicated astrobiological space mission is required. Venus Life Finder (VLF) missions encompass unique mission concepts with specialized instruments to search for habitability indicators, biosignatures and even life itself. A key in the search for life is direct capture, concentration and visualization of particles of biological potential. Here, we present a short overview of Fluid-Screen (FS) technology, a recent advancement in the dielectrophoretic (DEP) microbial particle capture, concentration and separation. Fluid-Screen is capable of capturing and separating biochemically diverse particles, including multicellular molds, eukaryotic cells, different species of bacteria and even viruses, based on particle dielectric properties. In this short communication, we discuss the possible implementation of Fluid-Screen in the context of the Venus Life Finder (VLF) missions, emphasizing the unique science output of the Fluid-Screen instrument. FS can be coupled with other highly sophisticated instruments such as an autofluorescence microscope or a laser desorption mass spectrometer (LDMS). We discuss possible configurations of Fluid-Screen that upon modification and testing, could be adapted for Venus. We discuss the unique science output of the Fluid-Screen technology that can capture biological particles in their native state and hold them in the focal plane of the microscope for the direct imaging of the captured material. We discuss the challenges for the proposed method posed by the concentrated sulfuric acid environment of Venus’ clouds. While Venus’ clouds are a particularly challenging environment, other bodies of the solar system, e.g., with liquid water present, might be especially suitable for Fluid-Screen application.
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Rapoport, Yuriy G., Oleg K. Cheremnykh, Volodymyr V. Koshovy, Mykola O. Melnik, Oleh L. Ivantyshyn, Roman T. Nogach, Yuriy A. Selivanov i in. "Ground-based acoustic parametric generator impact on the atmosphere and ionosphere in an active experiment". Annales Geophysicae 35, nr 1 (5.01.2017): 53–70. http://dx.doi.org/10.5194/angeo-35-53-2017.
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Abstract. We develop theoretical basics of active experiments with two beams of acoustic waves, radiated by a ground-based sound generator. These beams are transformed into atmospheric acoustic gravity waves (AGWs), which have parameters that enable them to penetrate to the altitudes of the ionospheric E and F regions where they influence the electron concentration of the ionosphere. Acoustic waves are generated by the ground-based parametric sound generator (PSG) at the two close frequencies. The main idea of the experiment is to design the output parameters of the PSG to build a cascade scheme of nonlinear wave frequency downshift transformations to provide the necessary conditions for their vertical propagation and to enable penetration to ionospheric altitudes. The PSG generates sound waves (SWs) with frequencies f1 = 600 and f2 = 625 Hz and large amplitudes (100–420 m s−1). Each of these waves is modulated with the frequency of 0.016 Hz. The novelty of the proposed analytical–numerical model is due to simultaneous accounting for nonlinearity, diffraction, losses, and dispersion and inclusion of the two-stage transformation (1) of the initial acoustic waves to the acoustic wave with the difference frequency Δf = f2 − f1 in the altitude ranges 0–0.1 km, in the strongly nonlinear regime, and (2) of the acoustic wave with the difference frequency to atmospheric acoustic gravity waves with the modulational frequency in the altitude ranges 0.1–20 km, which then reach the altitudes of the ionospheric E and F regions, in a practically linear regime. AGWs, nonlinearly transformed from the sound waves, launched by the two-frequency ground-based sound generator can increase the transparency of the ionosphere for the electromagnetic waves in HF (MHz) and VLF (kHz) ranges. The developed theoretical model can be used for interpreting an active experiment that includes the PSG impact on the atmosphere–ionosphere system, measurements of electromagnetic and acoustic fields, study of the variations in ionospheric transparency for the radio emissions from galactic radio sources, optical measurements, and the impact on atmospheric aerosols. The proposed approach can be useful for better understanding the mechanism of the acoustic channel of seismo-ionospheric coupling.
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Ayachi, M. "Mise au point d'une méthode de détermination de la température moyenne de la mésosphère à partir de la mesure de la vitesse de phase des ondes longues sur un trajet grande distance". Canadian Journal of Physics 71, nr 3-4 (1.03.1993): 106–14. http://dx.doi.org/10.1139/p93-016.
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The.mechanism of the Lyman α ionization of nitric oxide, which is mainly responsible for the formation of the D region, the lowest part of the ionosphere, is first briefly reviewed. From equations of the photochemical equilibrium, a model of the height distribution of the electron density is proposed as a function of the solar angle Θ and the scale height H, which is a function of the mesospheric temperature T. A method named Geoscanner based upon a set of curves that illustrate the theoretical relations between the phase of a continuous VLF radio wave for a long-distance transmission and the different parameters of the daytime atmosphere is described. This method is applied to analyse experimental data obtained by phase measurements for the 10.2 kHz transmission Trelew (Argentina) – Caen (France), nearly 12 000 km distant. It provides a mean value of the mesospheric temperature that is a characteristic of the studied path and day. The significance of such an integrated temperature, ranging between 190 and 200 K, is discussed.
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Yang, Shih-Sian, i Masashi Hayakawa. "Gravity Wave Activity in the Stratosphere before the 2011 Tohoku Earthquake as the Mechanism of Lithosphere-atmosphere-ionosphere Coupling". Entropy 22, nr 1 (16.01.2020): 110. http://dx.doi.org/10.3390/e22010110.
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The precursory atmospheric gravity wave (AGW) activity in the stratosphere has been investigated in our previous paper by studying an inland Kumamoto earthquake (EQ). We are interested in whether the same phenomenon occurs or not before another major EQ, especially an oceanic EQ. In this study, we have examined the stratospheric AGW activity before the oceanic 2011 Tohoku EQ (Mw 9.0), while using the temperature profiles that were retrieved from ERA5. The potential energy (EP) of AGW has enhanced from 3 to 7 March, 4–8 days before the EQ. The active region of the precursory AGW first appeared around the EQ epicenter, and then expanded omnidirectionally, but mainly toward the east, covering a wide area of 2500 km (in longitude) by 1500 km (in latitude). We also found the influence of the present AGW activity on some stratospheric parameters. The stratopause was heated and descended; the ozone concentration was also reduced and the zonal wind was reversed at the stratopause altitude before the EQ. These abnormalities of the stratospheric AGW and physical/chemical parameters are most significant on 5–6 March, which are found to be consistent in time and spatial distribution with the lower ionospheric perturbation, as detected by our VLF network observations. We have excluded the other probabilities by the processes of elimination and finally concluded that the abnormal phenomena observed in the present study are EQ precursors, although several potential sources can generate AGW activities and chemical variations in the stratosphere. The present paper shows that the abnormal stratospheric AGW activity has also been detected even before an oceanic EQ, and the AGW activity has obliquely propagated upward and further disturbed the lower ionosphere. This case study has provided further support to the AGW hypothesis of the lithosphere-atmosphere-ionosphere coupling process.
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Wang, Jianguo, Si Cheng, Li Cai, Yadong Fan, Mi Zhou, Quanxin Li i Yijun Huang. "Mapping Thunderstorm Electrical Structure in the Troposphere in Warm Season with VLF/LF Total Lightning Monitoring Data over the Pearl River Delta Region, China". Atmosphere 13, nr 7 (24.06.2022): 1015. http://dx.doi.org/10.3390/atmos13071015.
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Mapping the thunderstorm electrical structure could provide an effective way for lightning-sensitive facilities protection, such as aircraft and maritime assets. However, the weather radar that is normally used to forecast storms and rainfall mainly detects precipitation in the atmosphere and indicates the existence of liquid raindrops and ice particles by reflectivity. Here, we use intra-cloud events of eight thunderstorm days in the warm season, which are detected by VLF/LF Total Lightning monitoring system, to reveal the thunderstorm electrical structures in the 300 × 300 km area of the Pearl River Delta (PRD) region. The differences in height range in four types of time intervals and three types of intro-cloud events proportions are compared on 16 May. With the proportion between 20% and 80% in the time interval of 15 min, the height distribution and the electrical structure of eight thunderstorm days are clearly exhibited. The positive IC events lie in the average height between 7.5 and 12.4 km, while the negative IC events are located between 5.3 and 11.7 km. The electrical structures show the variations during the evolution process, with a dipole structure in most circumstances, while temporary reversions are identified in the initial and the dissipating stage of thunderstorms, presenting the inverted dipole and the tripole structures.
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Hudson, T. S., A. Horseman i J. Sugier. "Diurnal, Seasonal, and 11-yr Solar Cycle Variation Effects on the Virtual Ionosphere Reflection Height and Implications for the Met Office’s Lightning Detection System, ATDnet". Journal of Atmospheric and Oceanic Technology 33, nr 7 (lipiec 2016): 1429–41. http://dx.doi.org/10.1175/jtech-d-15-0133.1.
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AbstractThe virtual ionosphere reflection height variation is investigated temporally and spatially, with specific reference to the Met Office’s lightning detection network, the Arrival Time Difference Network (ATDnet). Data from this network, operating at 13.7 kHz, and a propagation model built by the Met Office based upon published theory were used to investigate this variation, specifically with regard to diurnal, seasonal, and 11-yr solar cycle variation. Variation over these temporal scales is chosen, since they correspond with variation in solar irradiance upon the earth’s atmosphere, something known to drive ionosphere height variation. The virtual ionosphere reflection height is found to vary diurnally from ~65 km for the period 1000–1600 UTC to ~80 km for the period 2200–0400 UTC, from 1 June to 31 August 2013 inclusive. A similar magnitude of variation is also observed seasonally, with the ionosphere height for daytime in August 2013 being ~64 km and for December 2013 being ~76 km. No significant variation is observed between the minimum and maximum of the last solar cycle, with a difference in ionosphere height of ~1 km at most. The potential impacts of these results upon a very low-frequency (VLF) lightning detection network such as ATDnet are discussed, with solutions such as subnetting and wave-mode dominance analysis examined.
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Palit, Sourav, Jean-Pierre Raulin i Sérgio Szpigel. "Response of Earth's Upper Atmosphere and VLF Propagation to Celestial X-Ray Ionization: Investigation With Monte Carlo Simulation and Long Wave Propagation Capability code". Journal of Geophysical Research: Space Physics 123, nr 12 (grudzień 2018): 10,224–10,238. http://dx.doi.org/10.1029/2018ja025992.
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Hayakawa, Masashi, Alexander Schekotov, Hiroki Yamaguchi i Yasuhide Hobara. "Observation of Ultra-Low-Frequency Wave Effects in Possible Association with the Fukushima Earthquake on 21 November 2016, and Lithosphere–Atmosphere–Ionosphere Coupling". Atmosphere 14, nr 8 (7.08.2023): 1255. http://dx.doi.org/10.3390/atmos14081255.
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The study presents seismogenic ULF (ultra-low-frequency) wave effects, as observed at our own new magnetic observatory at Asahi (geographic coordinates: 35.770° N, 140.695° E) in Chiba Prefecture. Our target earthquake (EQ) is a huge one offshore of Fukushima prefecture (37.353° N, 141.603° E) with a magnitude (M) of 7.4, which occurred at 20.59 h on November 21 UT, 2016. As a sampling frequency of 1 Hz was chosen for our induction magnetometer, we could detect both ULF wave effects: ULF radiation from the lithosphere, and the ULF depression effect, indicative of lower ionospheric perturbations. Observing the results of polarization analyses, we detected clear enhancements in ULF (frequency = 0.01–0.03 Hz) lithospheric radiation 14 days, 5 days, and 1 day before the EQ, and also observed a very obvious phenomenon of ULF (0.01–0.03 Hz) depression just 1 day prior to the EQ, which is regarded as the signature of lower ionospheric perturbations. These findings suggest that pre-EQ seismic activity must be present in the lithosphere, and also that the lower ionosphere was very much perturbed by the precursory effects of the Fukushima EQ. These new observational effects from our station have been compared with our previous investigations on different seismogenic topics for the same EQ, including the ULF observations at another magnetic observatory at Kakioka, belonging to the Japan Meteorological Agency (JMA), about 50 km north of our Asahi station, subionospheric VLF/LF propagation data (Japanese and Russian data), AGW (Atmospheric gravity wave) activity in the stratosphere, and satellite observation of particle precipitations. We have found that seismogenic anomalies of different parameters tend to happen just around the EQ day, but mainly before the EQ, and have found the chain-like tendency of the effects of the lithosphere, which seem to propagate upwards the lower ionosphere. Finally, we will try to gain a better understanding of the physical phenomena or mechanisms of the lithosphere–atmosphere–ionosphere coupling (LAIC) process during the EQ preparation phase.
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Surkov, V. V., i M. Hayakawa. "Underlying mechanisms of transient luminous events: a review". Annales Geophysicae 30, nr 8 (17.08.2012): 1185–212. http://dx.doi.org/10.5194/angeo-30-1185-2012.
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Abstract. Transient luminous events (TLEs) occasionally observed above a strong thunderstorm system have been the subject of a great deal of research during recent years. The main goal of this review is to introduce readers to recent theories of electrodynamics processes associated with TLEs. We examine the simplest versions of these theories in order to make their physics as transparent as possible. The study is begun with the conventional mechanism for air breakdown at stratospheric and mesospheric altitudes. An electron impact ionization and dissociative attachment to neutrals are discussed. A streamer size and mobility of electrons as a function of altitude in the atmosphere are estimated on the basis of similarity law. An alternative mechanism of air breakdown, runaway electron mechanism, is discussed. In this section we focus on a runaway breakdown field, characteristic length to increase avalanche of runaway electrons and on the role played by fast seed electrons in generation of the runaway breakdown. An effect of thunderclouds charge distribution on initiation of blue jets and gigantic jets is examined. A model in which the blue jet is treated as upward-propagating positive leader with a streamer zone/corona on the top is discussed. Sprite models based on streamer-like mechanism of air breakdown in the presence of atmospheric conductivity are reviewed. To analyze conditions for sprite generation, thunderstorm electric field arising just after positive cloud-to-ground stroke is compared with the thresholds for propagation of positively/negatively charged streamers and with runway breakdown. Our own estimate of tendril's length at the bottom of sprite is obtained to demonstrate that the runaway breakdown can trigger the streamer formation. In conclusion we discuss physical mechanisms of VLF (very low frequency) and ELF (extremely low frequency) phenomena associated with sprites.
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Moeckel, Chris, Imke de Pater i David DeBoer. "Ammonia Abundance Derived from Juno MWR and VLA Observations of Jupiter". Planetary Science Journal 4, nr 2 (1.02.2023): 25. http://dx.doi.org/10.3847/psj/acaf6b.
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Abstract The vertical distribution of trace gases in planetary atmospheres can be obtained with observations of the atmosphere’s thermal emission. Inverting radio observations to recover the atmospheric structure, however, is nontrivial, and the solutions are degenerate. We propose a modeling framework to prescribe a vertical distribution of trace gases that combines a thermochemical equilibrium model with a vertical temperature structure and compare these results to models where ammonia can vary between predefined pressure nodes. We compare these model to nadir brightness temperatures and limb-darkening parameters, together with their uncertainties, which we reduced from the raw Juno Microwave Radiometer (MWR) data set. We then apply this framework to MWR observations during Juno’s first years of operation (perijove passes 1–12) and to longitudinally averaged latitude scans taken with the upgraded Very Large Array. We use the model to constrain the distribution of ammonia between −60° and 60° latitude and down to 100 bars. We constrain the ammonia abundance to be 340.5 − 21.2 + 34.8 ppm ( 2.66 − 0.17 + 0.27 × solar abundance) and find a depletion of ammonia down to a depth of ∼20 bars, which supports the existence of processes that deplete the atmosphere below the ammonia and water cloud layers. At the equator we find an increase of ammonia with altitude, while the zones and belts in the midlatitudes can be traced down to levels where the atmosphere is well mixed. The latitudinal variation in the ammonia abundance appears to be opposite to that shown at higher altitudes, which supports the existence of a stacked-cell circulation model.
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Marchuk, Roman, Alexander Potapov i Vladimir Mishin. "Synchronous globally observable ultrashort-period pulses". Solar-Terrestrial Physics 8, nr 2 (30.06.2022): 47–55. http://dx.doi.org/10.12737/stp-82202207.
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We have studied the properties of impulsive geomagnetic disturbances, which are observed synchronously at the network of induction magnetometers of the Institute of Solar-Terrestrial Physics (ISTP SB RAS) and Canadian stations of the CARISMA project [Mann, et al., 2008]. A feature of the pulses we detected is that their frequency range (f~5–30 Hz) lies at the junction of the ranges of two known classes of electromagnetic oscillations: ultra-low-frequency (ULF) oscillations (f<5–10 Hz), or geomagnetic pulsations, and extra-low frequency (ELF) oscillations (f~30–300 Hz); therefore, the 5–30 Hz range is poorly studied. The work is of undoubted interest for physics of processes in the magnetosphere–ionosphere–atmosphere system. Morphological analysis of the pulses detected has been carried out using data from ISTP stations. As a result, we obtained statistical characteristics of the pulses, plotted their dynamic spectra, and determined a number of unusual properties that distinguish them, on the one hand, from geomagnetic pulsations of the pulsed type (irregular pulsations of the Pi1B type), and, on the other hand, from higher frequency ELF and VLF signals (atmospherics, whistlers, etc.). On the basis of the results, we have made an assumption that a source of the pulses under study can be electrical sprites caused by powerful thunderstorms at middle and low latitudes. Using the results obtained by Wang, et al. in 2019 on spatial and temporal fixation of sprites in North China, we have confirmed that ultra-short-period pulses occur following the emergence of sprites. Thunderstorm activity, both local and global, is considered to be one of the main sources of excitation of the ionospheric Alfvén resonator (IAR), which plays an important role in coupling the ionosphere and the magnetosphere. The pulsed oscillations of interest may be one of the agents through which the energy of thunderstorms is transferred to IAR, thereby including the atmosphere in the system considered.
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Singh, Raj, i Birbal Singh. "Anomalous subsurface VLF electric field changes related to India-Nepal border earthquake (M=5.3) of 4 April 2011 and their lithosphere – atmosphere coupling observed at Mathura". Journal of Atmospheric Electricity 33, nr 1 (2013): 31–39. http://dx.doi.org/10.1541/jae.33.31.
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Li, Guang Ming, Chang Jun Li i Quan Na Li. "Research of the VLF Atmospheric Noise Statistical Prediction". Applied Mechanics and Materials 716-717 (grudzień 2014): 1303–7. http://dx.doi.org/10.4028/www.scientific.net/amm.716-717.1303.
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The nature of the vlf atmospheric noise can have a dramatic effect on the performance of the vlf receivers. To understanding how the receivers will perform in different locations and time, the key is proper predicting the critical parameters of the vlf atmospheric noise. Based on the purpose, according to the historical data and the corresponding frequency and parameter variation chart, established the data fitting algorithm to predict the critical parameters of the vlf atmospheric noise. By simulating and comparing with the measured data, testified the effectiveness of the vlf atmospheric noise prediction method. To grasp the change rule of critical vlf noise parameters with time and geographical position is helpful to improve the vlf communication effectiveness.
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Marshall, R. A., U. S. Inan, T. Neubert, A. Hughes, G. Sátori, J. Bór, A. Collier i T. H. Allin. "Optical observations geomagnetically conjugate to sprite-producing lightning discharges". Annales Geophysicae 23, nr 6 (15.09.2005): 2231–37. http://dx.doi.org/10.5194/angeo-23-2231-2005.
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Abstract. Theoretical studies have predicted that large positive cloud-to-ground discharges can trigger a runaway avalanche process of relativistic electrons, forming a geomagnetically trapped electron beam. The beam may undergo pitch angle and energy scattering during its traverse of the Earth's magnetosphere, with a small percentage of electrons remaining in the loss cone and precipitating in the magnetically conjugate atmosphere. In particular, N2 1P and N2+1N optical emissions are expected to be observable. In July and August 2003, an attempt was made to detect these optical emissions, called "conjugate sprites", in correlation with sprite observations in Europe near . Sprite observations were made from the Observatoire du Pic du Midi (OMP) in the French Pyrenées, and VLF receivers were installed in Europe to detect causative sferics and ionospheric disturbances associated with sprites. In the Southern Hemisphere conjugate region, the Wide-angle Array for Sprite Photometry (WASP) was deployed at the South African Astronomical Observatory (SAAO), near Sutherland, South Africa, to observe optical emissions with a field-of-view magnetically conjugate to the Northern Hemisphere observing region. Observations at OMP revealed over 130 documented sprites, with WASP observations covering the conjugate region successfully for 30 of these events. However, no incidences of optical emissions in the conjugate hemisphere were found. Analysis of the conjugate optical data from SAAO, along with ELF energy measurements from Palmer Station, Antarctica, and charge-moment analysis, show that the lightning events during the course of this experiment likely had insufficient intensity to create a relativistic beam. Keywords. Ionosphere (Ionsophere-magnetosphere interactions; Ionospheric disturbances; Instruments and techniques)
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Raj Pal Singh, Sarita Sharma i Devbrat Pundhir. "Effect of VLF Electromagnetic Radiations Associated with Some Moderate Shallow Earthquakes (4.9 ≤ M ≤ 6, Depth ≤ 20 Km) on the Atmosphere as Observed in the Terrestrial Antenna at Mathura". Geomagnetism and Aeronomy 62, nr 5 (28.09.2022): 663–74. http://dx.doi.org/10.1134/s0016793222050140.
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Koshak, William J., Douglas M. Mach i Phillip M. Bitzer. "Mitigating VHF Lightning Source Retrieval Errors". Journal of Atmospheric and Oceanic Technology 35, nr 5 (maj 2018): 1033–52. http://dx.doi.org/10.1175/jtech-d-17-0041.1.
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AbstractThe problem of inferring the location and time of occurrence of a very high frequency (VHF) lightning source emission from Lightning Mapping Array (LMA) network time-of-arrival (TOA) measurements is closely examined in order to clarify the cause of retrieval errors and to determine how best to mitigate these errors. With regard to this inverse problem, the previous literature lacks a comprehensive discussion of the associated forward problem. Hence, the forward problem is analyzed in this study to better clarify why retrieval errors increase with increasing source horizontal range and/or decreasing source altitude. Further insight is obtained by performing carefully designed Monte Carlo inversion simulations that provide specific retrieval error plots, which in turn lead to clear recommendations for mitigating retrieval errors. Based on all of the numerical results, the following strategies are recommended for mitigating retrieval errors (when possible, and without obstructing the line of sight): expand the horizontal extent of the LMA network, maximize the vertical sensor baseline by using mountainous terrain if available, and improve TOA measurement timing accuracy. Adding sensors to the network is relatively ineffective, unless of course the addition of sensors expands the horizontal extent and/or vertical baseline of the network. It is also shown how the standard retrieval method can be generalized by considering, in addition to the regular (unpolarized) point VHF source, the polarized transient very low frequency/low frequency (VLF/LF) electric point dipole source. Multiple observations (i.e., VHF arrival time and power, and VLF/LF arrival time and electric field amplitude) are simultaneously implemented into the new generalized mathematical framework, and the potential benefits are indicated.
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Lizunov, G. V., V. Korepanov, A. A. Lukenyuk, O. V. Piankova i O. P. Fedorov. "SPACE PROJECT “IONOSAT – MICRO”: READINESS FOR IMPLEMENTATION". Kosmìčna nauka ì tehnologìâ 28, nr 6 (8.12.2022): 03–11. http://dx.doi.org/10.15407/knit2022.06.003.
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Ionosat-Micro is a fundamental scientific project devoted to the study of near-Earth space. The project is conceived as an answer to the challenges posed by the modern development of knowledge about Space Weather and the ionospheric responses to surface energy sources (such as weather phenomena, power lines operation, earthquakes and processes of their preparation, powerful technogenic hazards, etc.). Furthermore, the project Ionosat-Micro is a logical continuation and addition to previous ionospheric missions, such as Dynamics Explorer 2 (launched in 1982), Freja (1992), DEMETER (2004), Swarm (2013), and CSES (2018). The project is being prepared with the support and within the framework of The National Space Program of Ukraine and The Program of the National Academy of Sciences of Ukraine for Scientific Space Research. The article outlines the scientific principles of the project, describes the parameters of the space system being created, and the composition and operation logic of the scientific equipment. The project is to be implemented on board the satellite platform Microsat-M, which has been designed by Yuzhnoye State Design Office to conduct scientific and technological experiments. The planned satellite orbit is circular sun-synchronous with an inclination of 98 degrees and altitude of 600–700 km (orbital parameters, method and date of the launch are being clarified). Ionosat-Micro payload includes a set of scientific instruments designed to register the global structure and physical parameters of the neutral atmosphere and plasma, the structure and parameters of the space current systems and geomagnetic field, as well as the spectra and wave-forms of ULF-ELF-VLF electromagnetic perturbations. The Center for Collection, Processing, and Distribution of Measurement Data was created for the purpose of accumulating and targeted data processing.
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Schlegel, K., i M. Füllekrug. "A D-region conductivity model from EISCAT VHF measurements". Annales Geophysicae 20, nr 9 (30.09.2002): 1439–45. http://dx.doi.org/10.5194/angeo-20-1439-2002.
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Abstract. An easy-to-use model to evaluate conductivities at high and middle latitudes in the height range 70–100 km is presented. It is based on electron density profiles obtained with the EISCAT VHF radar during 11 years and on the neutral atmospheric model MSIS95. The model uses solar zenith angle, geomagnetic activity and season as input parameters. It was mainly constructed to study the properties of Schumann resonances that depend on such conductivity profiles.Key words. Meteorology and atmospheric dynamics (middle atmospheric dynamics) – Ionosphere (modeling and forecasting; ionosphere-atmosphere interaction)
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Worthington, R. M., R. D. Palmer i S. Fukao. "<i>Letter to the Editor</i>: Complete maps of the aspect sensitivity of VHF atmospheric radar echoes". Annales Geophysicae 17, nr 8 (31.08.1999): 1116–19. http://dx.doi.org/10.1007/s00585-999-1116-z.
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Abstract. Using the MU radar at Shigaraki, Japan (34.85°N, 136.10°E), we measure the power distribution pattern of VHF radar echoes from the mid-troposphere. The large number of radar beam-pointing directions (320) allows the mapping of echo power from 0° to 40° from zenith, and also the dependence on azimuth, which has not been achieved before at VHF wavelengths. The results show how vertical shear of the horizontal wind is associated with a definite skewing of the VHF echo power distribution, for beam angles as far as 30° or more from zenith, so that aspect sensitivity cannot be assumed negligible at any beam-pointing angle that most existing VHF radars are able to use. Consequently, the use of VHF echo power to calculate intensity of atmospheric turbulence, which assumes only isotropic backscatter at large beam zenith angles, will sometimes not be valid.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; instruments and techniques)
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Worthington, R. M. "Asymmetry of atmospheric microstructure over synoptic scales". Annales Geophysicae 19, nr 8 (31.08.2001): 921–24. http://dx.doi.org/10.5194/angeo-19-921-2001.
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Abstract. Distortions are often seen in the angular distribution of echo-power from VHF wind-profiling radars, suggesting that thin stable layers, within the air flow, are distorted and tilted from horizontal. In vertical shear of the horizontal wind, the distribution of the layer tilt angles becomes skewed. A case study using six days of VHF radar data and synoptic charts above western Europe indicates that this asymmetry of atmospheric microstructure can exist throughout the troposphere and lower stratosphere, above and below the jet wind maximum, over horizontal scales of thousands of kilometres.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; synoptic-scale meteorology; turbulence).
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Zhou, Jian Ping, i Guang Ming Li. "Research on the Frequency Spectrum Management Method of VLF Based on the Propagation Prediction Technology". Applied Mechanics and Materials 543-547 (marzec 2014): 2180–83. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.2180.
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VLF communication is one of the most effective means to command underwater platform. The spectrum resource of vlf communication is limited, so it is very important for enhance the reliability of vlf communication to strengthen the vlf communication spectrum management. It makes use of the well prediction of the vlf frequency band, to establish the signal field predicting model and atmospheric noise statistics predicting model respectively, predicts the field of signal and noise level, and then calculated the signal-to-noise ratio (SNR). According to the SNR distribution we can determine the relationship of the optimal communication frequency, time and location of receiver. So the efficiency of spectrum management for vlf communication can be enhanced.
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Fu, Gang, Yan Jun Wu i Qian He. "Simulation of VLF CSS System in Atmospheric Noise". Applied Mechanics and Materials 556-562 (maj 2014): 1874–78. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.1874.
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Very Low Frequency (VLF) communication is designed to operate in the frequency between 3 kHz and 30 kHz. The atmospheric noise generated by lightning phenomena is the main source of interference in VLF communications, it is rather difficult to detect the communication signal that not only merged in strong channel noise, but probably interfered by high-tension impulse caused by thunder. This paper, Alpha stable distribution noise model is proposed to simulate atmospheric noise firstly, then, we study a new technique of Chirp Spread Spectrum (CSS) communication based on Fractional Fourier Transform (FRFT), This paper studies a new VLF communication technique of the Chirp Spread Spectrum (CSS) communication based on Fractional Fourier Transform (FRFT), and it demodulates message utilizing energy gathering property of chirp signal in FRFT domain.
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Zhang, Yijun, Yang Zhang, Mengjin Zou, Jingxuan Wang, Yurui Li, Yadan Tan, Yuwen Feng, Huiyi Zhang i Shunxing Zhu. "Advances in Lightning Monitoring and Location Technology Research in China". Remote Sensing 14, nr 5 (7.03.2022): 1293. http://dx.doi.org/10.3390/rs14051293.
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Monitoring lightning and its location is important for understanding thunderstorm activity and revealing lightning discharge mechanisms. This is often realized based on very low-frequency/low-frequency (VLF/LF) signals, very high-frequency (VHF) signals, and optical radiation signals generated during the lightning discharge process. The development of lightning monitoring and location technology worldwide has largely evolved from a single station to multiple stations, from the return strokes (RSs) of cloud-to-ground (CG) lightning flashes to total lightning flashes, from total lightning flashes to lightning discharge channels, and from ground-based lightning observations to satellite-based lightning observations, all of which have aided our understanding of atmospheric electricity. Lightning monitoring and positioning technology in China has kept up with international advances. In terms of lightning monitoring based on VLF/LF signals, single-station positioning technology has been developed, and a nationwide CG lightning detection network has been built since the end of the twentieth century. Research on total lightning flash positioning technology began at the beginning of the 21st century, and precision total lightning flash positioning technology has improved significantly over the last 10 years. In terms of positioning technology based on VHF signals, narrowband interferometers and wideband interferometers have been developed, and long-baseline radiation source positioning technology and continuous interferometers have been developed over the last ten years, significantly improving the channel characterization ability of lightning locations. In terms of lightning monitoring based on optical signals, China has for the first time developed lightning mapping imagers loaded by geosynchronous satellites, providing an important means for large-scale and all-weather lightning monitoring.