Dynamical processes in the ionosphere following the moderate earthquake in Japan on 7 July 2018

Urgency. The Earth's interior layers – atmosphere – ionosphere – magnetosphere (EAIM) form a one system, which is open, dynamic, and nonlinear. There are direct and reverse, positive and negative linkages among the subsystems within the EAIM system, which are currently insufficiently studied. The release of energy from a high-power source in one of the subsystems triggers the interaction among the subsystems. In this paper, a moderate earthquake of Richter magnitude M » 6.6 is considered as such a source. The aim of the paper is to describe time variations in the characteristics of the HF radio waves observed along the radio propagation paths over the People's Republic of China during the earthquake of September 5, 2018 in Japan. Techniques and Methodology. To observe the temporal variations in the characteristics of radio waves, we used the multi-frequency multiple-path coherent radio system at the Harbin Engineering University. Broadcasting stations located in the People's Republic of China, the South Korea, Japan, Russia, and Mongolia are used as transmitters. The time variations in the Doppler spectra, the Doppler shift of frequency of the main mode, and signal amplitudes were subjected to analysis. The measurements were performed in the frequency range of 5 – 10 MHz over 14 radio propagation paths extending from ~ 900 km to 1800 km and having various orientations. The Doppler spectra are calculated in 7.5-s step with the root-mean-square Doppler line error of 0.02 Hz. Results. The response of the ionosphere to a moderate earthquake was observed and studied. The delay time of the assumed response and the apparent speed of propagation of the disturbances were estimated. It was demonstrated that the seismic shock was followed by Doppler spectra spreading and the Doppler frequency shift of the main mode varying with time quasi-periodically with an ~3-min period of infrasound and an ~20 – 30-min period of atmospheric gravity wave. Conclusions: Moderate earthquakes are capable of launching disturbances in the ionosphere detectable at distances of ~1000 km from the epicenter of earthquake.

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Section: Discussionunclassified

HF radio-wave characteristic variations over China during moderate earthquake in Japan on September 5, 2018

Luo¹,

Guo²,

Zheng

et al. 2019

Visnyk of V.N. Karazin Kharkiv National University, Series “Radio Physics and Electronics”

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“…A negative disturbance of −5 TECu occurred on 7 April and a significant negative disturbance of −10 TECu occurred on 15 April. Figures [16][17][18] show the time series at AIRA, SHAO, and TSK2 stations which are slightly far from the epicenter. We can see a similar phenomenon to Figure 15.…”

Section: Analysis Of Ionospheric Disturbances Prior To 2016 Kumamoto Earthquakementioning

confidence: 99%

“…These events are widely observed and provide good research cases for studying various ionospheric variations [ 13 ]. Earthquakes and other natural disasters occur frequently in Japan, and there are often different types of widely observed and analyzed ionospheric disturbances that last for a period of time before the earthquake [ 14 , 15 , 16 ], which may be used as important bases for analyzing and forecasting earthquakes. When a geomagnetic storm occurs, strong ionospheric density irregularities are generated, showing depletions (bubbles), enhancements (blobs), and scintillation [ 17 , 18 ], and they are all formed in the F layer of the ionosphere [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

Study of Spatial and Temporal Variations of Ionospheric Total Electron Content in Japan, during 2014–2019 and the 2016 Kumamoto Earthquake

Yao

Kong

2021

Sensors

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There are a large number of excellent research cases in Global Navigation Satellite System (GNSS) positioning and disaster prediction in Japan region, where the simulation and prediction of total electron content (TEC) is a powerful research method. In this study, we used the data of the GNSS Earth Observation Network (GEONET) established by the Geographical Survey Institute of Japan (GSI) to compare the performance of two regional ionospheric models in Japan, in which the spherical cap harmonic (SCH) model has the best performance. In this paper, we investigated the spatial and temporal variations of ionospheric TEC in Japan and their relationship with latitude, longitude, seasons, and solar activity. The results show that the TEC in Japan increases as the latitude decreases, with the highest average TEC in spring and summer and the lowest in winter, and has a strong correlation with solar activity. In addition, the observation and analysis of ionospheric disturbances over Japan before the 2016 Kumamoto earthquake and geomagnetic storms showed that GNSS observing of ionospheric TEC seems to be very effective in forecasting natural disasters and monitoring space weather.

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“…From 12:00 UT to 17:00 UT on 31 August 2019, virtually all propagation paths exhibited a quasiperiodicity in fD(t) at ~30 min period, T, and ~0.4-0.6 Hz amplitude, fDa. Given the fDa, the amplitude of variations in the electron density can be estimated by employing the following relation (Guo et al, 2019a(Guo et al, , 2020Chernogor et al, 2020):…”

Section: Wavelike Disturbance Effectsmentioning

confidence: 99%

Dynamic processes in the magnetic field and in the ionosphere during the 30 August–2 September, 2019 geospace storm

Luo

Черногор

Гармаш

et al. 2020

Preprint

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Abstract. Back at the end of the last century, L. F. Chernogor validated the concept that geospace storms are comprised of synergistically coupled magnetic storms, ionospheric storms, atmospheric storms, and storms in the electric field originating in the magnetosphere, the ionosphere and the atmosphere (i.e., electric storms). Their joint studies require the employment of multiple-method approach to the Sun–interplanetary medium–magnetosphere–ionosphere–atmosphere – Earth system. This study provides general analysis of the 30 August–2 September, 2019 geospace storm, the analysis of disturbances in the geomagnetic field and in the ionosphere, as well as the influence of the ionospheric storm on the characteristics of HF radio waves over the People's Republic of China. A unique feature of the geospace storm under study is its duration, of up to four days. The main results of the study are as follows. The energy and power of the geospace storm have been estimated to be 1.5 PJ and 15 GW, and thus this storm is weak. The energy and power of the magnetic storm have been estimated to be 1.5 PJ and 9 GW, i.e., this storm is moderate, and a unique feature of this storm is the duration of the main phase, of up to two days. The recovery phase also was lengthy, no less than two days. On 31 August 2019 and on 1 September 2019, the variations in the H and D components attained 60–70 nT, while the Z-component variations did not exceed 20 nT. On 31 August 2019 and on 1 September 2019, the level of fluctuations in the geomagnetic field in the 100–1000 s period range increased from from 0.2–0.3 nT to 2–4 nT, while the energy of the oscillations showed a maximum in the 300–400 s to 700–900 s period range. The geospace storm was accompanied by a moderate to strong negative ionospheric storm. During 31 August 2019 and 1 September 2019, the electron density in the ionospheric F region reduced by a factor of 1.4 to 2.4 times as compared to the values on the reference day. The geospace storm gave rise to appreciable disturbances also in the ionospheric E region, as well as in the Es layer. In the course of the ionospheric storm, the altitude of reflection of radiowaves could sharply increase from about 150 km to approximately 300–310 km. The geospace storm was accompanied by the generation of atmospheric gravity waves modulating the ionospheric electron density. For the about 30 min period oscillation, the amplitude of the electron density disturbances could attain about 40 %, while it did not exceed 6 % for the about 15 min period. The results obtained have made a contribution to understanding of the geospace storm physics, to developing theoretical and empirical models of geospace storms, to the acquisition of detailed understanding of the adverse effects that geospace storms have on radiowave propagation and to applying that knowledge to effective forecasting these adverse influences.

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Dynamical processes in the ionosphere following the moderate earthquake in Japan on 7 July 2018

Cited by 35 publications

References 38 publications

HF radio-wave characteristic variations over China during moderate earthquake in Japan on September 5, 2018

HF radio-wave characteristic variations over China during moderate earthquake in Japan on September 5, 2018

Study of Spatial and Temporal Variations of Ionospheric Total Electron Content in Japan, during 2014–2019 and the 2016 Kumamoto Earthquake

Dynamic processes in the magnetic field and in the ionosphere during the 30 August–2 September, 2019 geospace storm

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