Possible ionospheric disturbances relating to the May 12, 2008, MsS.0 Wenchuan earthquake were identified by Global Positioning System (GPS)-derived total electron content (TEC), ion- osonde observations, the glob...Possible ionospheric disturbances relating to the May 12, 2008, MsS.0 Wenchuan earthquake were identified by Global Positioning System (GPS)-derived total electron content (TEC), ion- osonde observations, the global ionospheric map (GIM), and electron density profiles detected by the Constellation Observation System for Meteorology Ionosphere and Climate (COSMIC). We applied a statistical test to detect anomalous TEC signals and found that a unique enhancement in TEC, recorded at 16 GPS stations, appeared on May 9, 2008. The critical fre- quency at F2 peak (foF2), observed by the Chinese ionosondes, and maximal plasma frequency, derived from COSMIC data, revealed a characteristic similar to GPS TEC variations. The GIM showed that the anomalous variations of May 9 were located southeast of the epicenter. Using GPS data from 13 stations near the epicenter, we analyzed the TEC variations of satellite orbit traces during 04:00-11:00 UT. We found that TEC decreased to the east and increased to the southeast of the epicenter during this period. Results showed that the abnormal disturbance on May 9 was probably an ionosphenc precursor of the Wenchuan earthquake of May 12, 2008.展开更多
An earthquake with a magnitude of Ms7.3 hit Yutian in the Xinjiang Uygur Autonomous Region on February 14, 2014. This research investigates the interference phenomena in solar activities and geomagnetics, and adopts t...An earthquake with a magnitude of Ms7.3 hit Yutian in the Xinjiang Uygur Autonomous Region on February 14, 2014. This research investigates the interference phenomena in solar activities and geomagnetics, and adopts the quartile method to analyze the Global Ionosphere Map (GIM) Vertical Total Electron Content (VTEC) data provided by the Center for Orbit Determination in Europe (CODE), as well as the difference between GIM VTEC and International Reference Ionosphere (IRI) VTEC data. The ionospheric VTEC disturbances at the earthquake epicenter are examined before and after the event. At UTC 8:00 on February 2, a strong VTEC disturbance emerged in the sky near the epicenter. A strong VTEC disturbance also emerged in the sky of the southern Hemisphere area, which is symmetric with the areas north of the equator. The methods used in analysis of the difference between GIM VTEC and IRI VTEC information can effectively fill the gaps in analysis that uses only the GIM VTEC data.展开更多
In the equatorial region,deep amplitude fading in global positioning system(GPS)signals frequently occurs during the strong ionospheric scintillation,it can lead to the loss of lock in GPS carrier tracking loops,and r...In the equatorial region,deep amplitude fading in global positioning system(GPS)signals frequently occurs during the strong ionospheric scintillation,it can lead to the loss of lock in GPS carrier tracking loops,and result in increased positioning error and even navigation interruption.The relationships between amplitude scintillation indices and detrended carrier frequency are investigated,based on GPS L1 C/A signals during the last peak of the solar cycle at the low latitude site of São Josédos Campos,Brazil(23.2S,45.9W)from 2013 to 2015.Corresponding mathematic model of the probability distribution function is built for the first time to provide statistical analysis on the above relationships.The results show that the standard carrier frequencies reveal an almost linear relation with the amplitude scintillation indices.Moreover,the frequency widths of detrended frequency are proportional to levels of amplitude scintillation when the value of the peak probability is lower than the corresponding boundary.A conclusion can be drawn that different levels of amplitude scintillation will influence the fluctuation of the carrier frequency.The analysis will provide useful guidance to set the receiver’s bandwidth with respect to the different scintillation levels and design the advanced tracking algorithms to improve the robustness and precision of the GPS receiver.展开更多
Ionosphere is an important layer of atmosphere which is under constant forcing from both below due to gravitational, geomagnetic and seismic activities, and above due to solar wind and galactic radiation. Spatio-tempo...Ionosphere is an important layer of atmosphere which is under constant forcing from both below due to gravitational, geomagnetic and seismic activities, and above due to solar wind and galactic radiation. Spatio-temporal variability of ionosphere is made up of two major components that can be listed as spatio-temporal trends and secondary variabilities that are due to disturbances in the geomagnetic field, gravitational waves and coupling of seismic activities into the upper atmosphere and ionosphere. Some of these second order variabilities generate wave-like oscillations in the ionosphere which propagate at a certain frequency, duration and velocity. These oscillations cause major problems for navigation and guidance systems that utilize GNSS (Global Navigation Satellite Systems). In this study, the frequency and duration of wave-like oscillations are determined using a DFT (Discrete Fourier Transform) based algo- rithm over the STEC (slant total electron content) values estimated from single GPS (Global Positioning System) station. The performance of the developed method, namely IONOLAB-FFT, is first determined using synthetic oscillations with known frequencies and durations. Then, IONOLAB-FFr is applied to STEC data from various midlatitude GPS stations for detection of frequency and duration of both medium and large scale TIDs (traveling ionospheric disturbances). It is observed that IONOLAB-FFr can estimate TIDs with more than 80% accuracy for the following cases: frequencies from 0.6 mHz to 2.4 mHz and durations longer than 10 min; frequencies from 0.15 mHz to 0.6 mHz and durations longer than 50 min; fre- quencies higher than 0.29 mHz and durations longer than 50 rain.展开更多
OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over ...OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over the Northeast region in Brazil.On the night of September 16 to 17,2020,an EPB was observed propagating eastward,in an apparent fossil stage,until it interacted with a dark band electrified MSTID(e MSTID).After the interaction,four EPBs merged,followed by an abrupt southward development and bifurcations.Analysis of the data suggests that an eastward polarization electric field,induced by the dark band e MSTID,forced the EPB into an upward drift,growing latitudinally along the magnetic field lines and then bifurcating.展开更多
Based on the case studies and statistical analysis of earthquake-related ionospheric disturbances mainly from DEMETER satellite, ground-based GPS and ionosounding data, this paper summarizes the statisw tical characte...Based on the case studies and statistical analysis of earthquake-related ionospheric disturbances mainly from DEMETER satellite, ground-based GPS and ionosounding data, this paper summarizes the statisw tical characteristics of earthquake-related ionospheric disturbances, including electromagnetic emissions, plasma perturbations and variation of energetic particle flux. According to the main results done by Chinese scientists, fusing with the existed study from global researches, seismo-ionospheric disturbances usually occurred a few days or hours before earthquake occurrence. Paralleling to these case studies, lithosphere-atmosphere-ionosphere (LAI) coupling mechanisms are checked and optimized. A thermo-electric model was proposed to explain the seismo-electromagnetic effects before earthquakes. A propagation model was put forward to explain the electromagnetic waves into the ionosphere. According to the requirement of earthquake prediction research, China seismo-electromagnetic satellite, the first space-based platform of Chinese earthquake stereoscopic observation system, is proposed and planned to launch at about the end of 2014. It focuses on checking the LAI model and distinguishing earthquake-related ionospheric disturbance. The preliminary design for the satellite will adopt CAST-2000 platform with eight payloads onboard. It is believed that the satellite will work together with the ground monitoring network to improve the capability to capture seismo-electromagnetic information, which is beneficial for earthquake monitoring and prediction researches.展开更多
Based on the ionospheric electromagnetic data observed on DEMETER satellite of France, the ionospheric electromagnetic signals were analyzed within 10 days before Chile M7.9 earthquake on November 14, 2007. It is foun...Based on the ionospheric electromagnetic data observed on DEMETER satellite of France, the ionospheric electromagnetic signals were analyzed within 10 days before Chile M7.9 earthquake on November 14, 2007. It is found that, low frequency electromagnetic disturbances began to increase in a large scale of latitude, and reached to a maximum one week prior to the earthquake, and at about three days before the quake, the peak values shifted to lower latitude. Taking three days as a group, spatial images of a few parameters were analyzed, from which it can be seen during the five days prior to this earthquake, the amplitude and scale of anomalies are enlarged, while the epicenter is located at the boundary of anomalous region. The anomalous tempo-spatial variation in electron density prior to the earthquake were also obtained in terms of tracing the data from revisited orbits in half a year prior to the quake.展开更多
The ionospheric effect from solar activity can be seen as the background in the process of detecting the ionospheric precursor prior to strong earthquakes.The ionospheric variation induced by the forthcoming earthquak...The ionospheric effect from solar activity can be seen as the background in the process of detecting the ionospheric precursor prior to strong earthquakes.The ionospheric variation induced by the forthcoming earthquake can be covered by the strong solar background during the period of high solar activity.The issue of how to remove the ionospheric effect from solar radiation is of outstanding significance.In this paper,a method of Empirical Mode Decomposition(EMD) is used to eliminate the solar background.As a case study,the global ionospheric map TEC before the M9.0 Tohoku earthquake on 11 March 2011 is analyzed.After the effect of solar radiation is removed using the EMD method,the precursor of the imminent earthquake is more obvious.The ionospheric anomaly had a local character and only appeared close to the earthquake epicenter while the useful signals were covered by the solar radiation background with traditional method,which implies that the EMD method is effective in eliminating solar radiation background.展开更多
The seismo-ionospheric anomalies may provide some insights about the earthquake.However,preseismic ionospheric anomalies are still challenging.In this paper,seismo-ionospheric anomalies are investigated before the Sep...The seismo-ionospheric anomalies may provide some insights about the earthquake.However,preseismic ionospheric anomalies are still challenging.In this paper,seismo-ionospheric anomalies are investigated before the September 24,2013(Mw=7.7)Awaran(Pakistan)earthquake from GPS TEC(Total Electron Content)and COSMIC(Constellation Observing System for Meteorology,Ionosphere and Climate)data.The TEC data are showing anomalies on September 21,2013.The abnormality detected in the temporal data is about 10 TECU beyond the 30-day running median.The percentage deviation of the TEC anomaly on September 21,is 30% above the upper confidence interval.The anomalies prevail 5 in Latitude and 10 in Longitude over the epicenter.The spatial and temporal data of TEC showed anomalies in TEC from UT=08 to UT=12.In addition,the enhancement on September 21,2013 is also very significant in COSMIC data.The results of COSMIC completely agreed with GPS TEC anomalies on September 21,2013.The percentage deviation of the peak plasma frequency on September 21 is 5% of the normal distribution.The storm indices are quiet before and after the earthquake.The pre-sesimic ionospheric anomalies are most probably associated with the 2013 Mw=7.7 Awaran(Pakistan)earthquake.展开更多
This paper analyzes the state of the ionosphere during two geomagnetic storms of a different intensity evolving in different sectors of local time in different seasons. There were used the data from a network of ionos...This paper analyzes the state of the ionosphere during two geomagnetic storms of a different intensity evolving in different sectors of local time in different seasons. There were used the data from a network of ionospheric stations located in the opposite longitudinal sectors of 80°-150° E and 250°-310° E.This analysis has permitted us to conclude that the detected differences in the variations of the disturbances are likely to be determined by the local time difference of the geomagnetic storm development, its intensity and by the different illumination conditions of the ionosphere.展开更多
Hunga Tonga-Hunga Ha’apai climactic eruption on January 15,2022,released enormous energy that affected the ionosphere over the Pacific Rim.We analyzed ionospheric disturbance following volcanic eruptions using near-f...Hunga Tonga-Hunga Ha’apai climactic eruption on January 15,2022,released enormous energy that affected the ionosphere over the Pacific Rim.We analyzed ionospheric disturbance following volcanic eruptions using near-field(<1000 km),regional(1000–5000 km),and far-field(5000–12000 km) global positioning system(GPS) observations.The results indicate that the near-field ionospheric perturbation that occurred 8–15 min after the cataclysmic eruption was mainly derived from the shock wave(~1000 m/s) generated by the blast,while the low-frequency branch with long-distance propagation characteristics over the regional and the far-field was mainly associated with atmospheric Lamb waves(~330 m/s).Moreover,the amplitude of disturbance and background total electron content(TEC) are related proportionally.The intensity of the volcanic eruption and the background ionospheric conditions determine the magnitude of ionospheric responses.TEC perturbations were invisible on the reference days.Furthermore,the source location and onset time were calculated using the ray tracing technique,which confirms that the Tonga event triggered the ionospheric anomaly beyond the crater.Finally,the change in the frequency of the perturbations coincided with the arrival of the initial tsunami,implying the generation of a meteotsunami.展开更多
同全球导航卫星系统(global navigation satellite system, GNSS)获取电离层总电子含量(total electron content, TEC)数据相比,传统的电离层垂测、斜测等短波段数据具有特征参数丰富、高度分辨率高、历史数据多等优点。为利用电离层垂...同全球导航卫星系统(global navigation satellite system, GNSS)获取电离层总电子含量(total electron content, TEC)数据相比,传统的电离层垂测、斜测等短波段数据具有特征参数丰富、高度分辨率高、历史数据多等优点。为利用电离层垂测和斜测数据,研究地下核爆引起的电离层扰动。利用2016年1月6日朝鲜地下核试验当天的斜测、垂测数据分析电离层扰动现象。结果表明,本次地下核爆造成的行波电离层扰动为小尺度电离层扰动,传播速度为150.3~158.7 m/s。同时核爆发生后0.5 h在距离爆点421.4 km处,观测到F2层临界频率(critical frequency of the F2layer, foF2)较月中值增加了0.7 MHz,较1月5日、1月7日在协调世界时(coordinated universal time, UTC)2:00 UTC的增加了0.5 MHz,极有可能是地下核爆通过岩石圈-大气圈-电离层圈耦合机制造成电离层电子浓度增加。本文分析结果与其他文献资料非常吻合。由此可见,基于短波段电离层探测方式感知电离层扰动从而实现地下核爆炸事件的监测,是一种有效的核爆电离层效应监测手段,可与其他直接监测手段相印证,提高核爆事件监测能力。展开更多
Here we report two cases of coseismic ionospheric disturbances observed through a GPS network in China after the great Wenchuan earthquake at 06:28 UT on 12 May,2008.One is detected 7.9 min after the earthquake and ha...Here we report two cases of coseismic ionospheric disturbances observed through a GPS network in China after the great Wenchuan earthquake at 06:28 UT on 12 May,2008.One is detected 7.9 min after the earthquake and had an intensive"N"shape oscillated waveform with a pronounced amplitude of about 1 TECU,which propagates approximately southward to the distance about 1000 km with the horizontal phase velocity of 600±84 m/s and the period of 9.5±1.3 min.The other is detected8.5 min after the earthquake and has an oscillated waveform more like a positive pulse with an amplitude of about 0.5 TECU,which propagates eastward to the distance about 800 km with the horizontal phase velocity of 720±59 m/s and the period of7.4±0.8 min.These two coseismic ionospheric disturbances are caused by the acoustic gravity waves excited by partial transformation of the acoustic waves originated from the energy release of the earthquake,somewhere near the epicenter.The directional preferences of these two coseismic ionospheric disturbances may be associated with the oblique geomagnetic field lines and the background winds filtering effect.展开更多
Larger-scale traveling ionospheric disturbances (LSTIDs) are studied using the total electron content (TEC) data observed from 246 GPS receivers in and around China during the medium storm on 28 May 2011. It is the fi...Larger-scale traveling ionospheric disturbances (LSTIDs) are studied using the total electron content (TEC) data observed from 246 GPS receivers in and around China during the medium storm on 28 May 2011. It is the first attempt to get the two-dimensional TEC perturbation maps in China. Two LSTID events are detected: one is in southwestern China before midnight propagating from low to middle latitude to the distance of about 1200 km with the phase front extending to about 500 km, and the other is in northeastern China after midnight propagating from middle to low latitudes to the distance of about 1200 km with the phase front extending to nearly 1400 km. By using the multichannel maximum-entropy method, we get the propagation parameters of these two LSTIDs. The LSTID that occurs before midnight has a higher horizontal phase velocity and a larger damping rate corresponding to the after midnight LSTID, and this may be caused by the relatively large vertical background TEC 0 and high atmospheric temperature in the southwest of China before midnight. According to the variations of magnetic H component observed in high latitudes, the source region for the after midnight LSTID is likely to be located 1400-2600 km east of 140°E and north of 42°N; the before midnight LSTID is propably excited by the atmospheric gravity waves (AGWs) generated by the Joule heating of the equatorial electrojet.展开更多
The paper examines the propagation direction and velocity of large-scale traveling ionospheric disturbances (LST1Ds) during extreme geomagnetic storms in the 23rd solar cycle (e.g., October 2003 and November 2003 s...The paper examines the propagation direction and velocity of large-scale traveling ionospheric disturbances (LST1Ds) during extreme geomagnetic storms in the 23rd solar cycle (e.g., October 2003 and November 2003 storms) using GPS observations. In the analysis, the time delay between the vertical total electron content (VTEC) structures at Scott Base, McMurdo, Davis and Casey GPS stations and the distance between these stations were the main parameters in the determination of LSTIDs propagation speed and direction. The observations during October and November 2003 storms show obvious time delay between the total electron content (TEC) enhancement signatures at these stations. The time delay suggests a movement of the ionospheric disturbances from higher to lower latitudes during the October storm with a velocity of 800-1 200 m/s and poleward propagation of LSTIDs during the November storm with a ve- locity of 300-400 m/s. The equatorward or poleward expansion of LSTIDs during the October and November 2003 storms is probably caused by the disturbances of the neutral temperature occurring close to the dayside convection throat or by the neutral wind oscillation induced by atmospheric gravity waves (AGW) launched from the aurora region.展开更多
This paper presents simulated results of the ionospheric behavior during few geomagnetic storms,which were occurred in the different seasons. The numerical model for ionosphere-plasmasphere coupling was used to interp...This paper presents simulated results of the ionospheric behavior during few geomagnetic storms,which were occurred in the different seasons. The numerical model for ionosphere-plasmasphere coupling was used to interpret the observed variation of ionosphere structure. Reasons why the positive storms are dominant in the winter whereas the negative ones are dominant in the summer season present the special interest for the mid-latitude ionosphere. A theoretical analysis of the processes controlling the ionospheric response to the geomagnetic storms has showed a good agreement between the simulated results and measurements, as well as the crucial role of the neutral composition variations to fit the calculated and the observed ionospheric parameters.展开更多
基金supported financially by Science for Earthquake Resilience(XH14064Y)the open foundation of the State Key Laboratory of Geodesy and Earth's Dynamics(SKLGED2014-5-2-E)
文摘Possible ionospheric disturbances relating to the May 12, 2008, MsS.0 Wenchuan earthquake were identified by Global Positioning System (GPS)-derived total electron content (TEC), ion- osonde observations, the global ionospheric map (GIM), and electron density profiles detected by the Constellation Observation System for Meteorology Ionosphere and Climate (COSMIC). We applied a statistical test to detect anomalous TEC signals and found that a unique enhancement in TEC, recorded at 16 GPS stations, appeared on May 9, 2008. The critical fre- quency at F2 peak (foF2), observed by the Chinese ionosondes, and maximal plasma frequency, derived from COSMIC data, revealed a characteristic similar to GPS TEC variations. The GIM showed that the anomalous variations of May 9 were located southeast of the epicenter. Using GPS data from 13 stations near the epicenter, we analyzed the TEC variations of satellite orbit traces during 04:00-11:00 UT. We found that TEC decreased to the east and increased to the southeast of the epicenter during this period. Results showed that the abnormal disturbance on May 9 was probably an ionosphenc precursor of the Wenchuan earthquake of May 12, 2008.
基金supported by the National Natural Science Foundation of China(41304036)the Natural Science Foundation of Colleges and Universities in Jiangsu Province(12KJB420003)+1 种基金the Innovation and Entrepreneurship Training Program of Chinese College Students(201310300040)Teaching Material Construction Projects of Atmospheric Sciences and Environmental Meteorology of NUIST(SYJC2014C13)
文摘An earthquake with a magnitude of Ms7.3 hit Yutian in the Xinjiang Uygur Autonomous Region on February 14, 2014. This research investigates the interference phenomena in solar activities and geomagnetics, and adopts the quartile method to analyze the Global Ionosphere Map (GIM) Vertical Total Electron Content (VTEC) data provided by the Center for Orbit Determination in Europe (CODE), as well as the difference between GIM VTEC and International Reference Ionosphere (IRI) VTEC data. The ionospheric VTEC disturbances at the earthquake epicenter are examined before and after the event. At UTC 8:00 on February 2, a strong VTEC disturbance emerged in the sky near the epicenter. A strong VTEC disturbance also emerged in the sky of the southern Hemisphere area, which is symmetric with the areas north of the equator. The methods used in analysis of the difference between GIM VTEC and IRI VTEC information can effectively fill the gaps in analysis that uses only the GIM VTEC data.
基金This work was supported by the National Key Research and Development Plan of China(2018YFB0505103)the National Natural Science Foundation of China(61873064)the Science and Technology Project of State Grid Corporation of China(SGSHJX00KXJS1901531).
文摘In the equatorial region,deep amplitude fading in global positioning system(GPS)signals frequently occurs during the strong ionospheric scintillation,it can lead to the loss of lock in GPS carrier tracking loops,and result in increased positioning error and even navigation interruption.The relationships between amplitude scintillation indices and detrended carrier frequency are investigated,based on GPS L1 C/A signals during the last peak of the solar cycle at the low latitude site of São Josédos Campos,Brazil(23.2S,45.9W)from 2013 to 2015.Corresponding mathematic model of the probability distribution function is built for the first time to provide statistical analysis on the above relationships.The results show that the standard carrier frequencies reveal an almost linear relation with the amplitude scintillation indices.Moreover,the frequency widths of detrended frequency are proportional to levels of amplitude scintillation when the value of the peak probability is lower than the corresponding boundary.A conclusion can be drawn that different levels of amplitude scintillation will influence the fluctuation of the carrier frequency.The analysis will provide useful guidance to set the receiver’s bandwidth with respect to the different scintillation levels and design the advanced tracking algorithms to improve the robustness and precision of the GPS receiver.
文摘Ionosphere is an important layer of atmosphere which is under constant forcing from both below due to gravitational, geomagnetic and seismic activities, and above due to solar wind and galactic radiation. Spatio-temporal variability of ionosphere is made up of two major components that can be listed as spatio-temporal trends and secondary variabilities that are due to disturbances in the geomagnetic field, gravitational waves and coupling of seismic activities into the upper atmosphere and ionosphere. Some of these second order variabilities generate wave-like oscillations in the ionosphere which propagate at a certain frequency, duration and velocity. These oscillations cause major problems for navigation and guidance systems that utilize GNSS (Global Navigation Satellite Systems). In this study, the frequency and duration of wave-like oscillations are determined using a DFT (Discrete Fourier Transform) based algo- rithm over the STEC (slant total electron content) values estimated from single GPS (Global Positioning System) station. The performance of the developed method, namely IONOLAB-FFT, is first determined using synthetic oscillations with known frequencies and durations. Then, IONOLAB-FFr is applied to STEC data from various midlatitude GPS stations for detection of frequency and duration of both medium and large scale TIDs (traveling ionospheric disturbances). It is observed that IONOLAB-FFr can estimate TIDs with more than 80% accuracy for the following cases: frequencies from 0.6 mHz to 2.4 mHz and durations longer than 10 min; frequencies from 0.15 mHz to 0.6 mHz and durations longer than 50 min; fre- quencies higher than 0.29 mHz and durations longer than 50 rain.
基金supported by Coordenacao de Aperfeicoamento de Pessoal de Nível Superior(CAPES)by Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq),under the processes 470589/2012-4,305461/2015-0,303511/2017-6,307653/2017-0,and 169815/2017-0the Fundacao de AmparoàPesquisa do Estado de Sao Paulo(FAPESP)under the process 2018/09066-8。
文摘OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over the Northeast region in Brazil.On the night of September 16 to 17,2020,an EPB was observed propagating eastward,in an apparent fossil stage,until it interacted with a dark band electrified MSTID(e MSTID).After the interaction,four EPBs merged,followed by an abrupt southward development and bifurcations.Analysis of the data suggests that an eastward polarization electric field,induced by the dark band e MSTID,forced the EPB into an upward drift,growing latitudinally along the magnetic field lines and then bifurcating.
基金funded by National Key Technology R&D Program in the 11th Five Year Plan of China (2008BAC35B00)the international cooperation project(2009DFA21480)
文摘Based on the case studies and statistical analysis of earthquake-related ionospheric disturbances mainly from DEMETER satellite, ground-based GPS and ionosounding data, this paper summarizes the statisw tical characteristics of earthquake-related ionospheric disturbances, including electromagnetic emissions, plasma perturbations and variation of energetic particle flux. According to the main results done by Chinese scientists, fusing with the existed study from global researches, seismo-ionospheric disturbances usually occurred a few days or hours before earthquake occurrence. Paralleling to these case studies, lithosphere-atmosphere-ionosphere (LAI) coupling mechanisms are checked and optimized. A thermo-electric model was proposed to explain the seismo-electromagnetic effects before earthquakes. A propagation model was put forward to explain the electromagnetic waves into the ionosphere. According to the requirement of earthquake prediction research, China seismo-electromagnetic satellite, the first space-based platform of Chinese earthquake stereoscopic observation system, is proposed and planned to launch at about the end of 2014. It focuses on checking the LAI model and distinguishing earthquake-related ionospheric disturbance. The preliminary design for the satellite will adopt CAST-2000 platform with eight payloads onboard. It is believed that the satellite will work together with the ground monitoring network to improve the capability to capture seismo-electromagnetic information, which is beneficial for earthquake monitoring and prediction researches.
基金supported by Chinese National Science and Technology Program (2008BAC35B01)Basic Research Project from Institute of Earthquake Science, China Earthquake Administration
文摘Based on the ionospheric electromagnetic data observed on DEMETER satellite of France, the ionospheric electromagnetic signals were analyzed within 10 days before Chile M7.9 earthquake on November 14, 2007. It is found that, low frequency electromagnetic disturbances began to increase in a large scale of latitude, and reached to a maximum one week prior to the earthquake, and at about three days before the quake, the peak values shifted to lower latitude. Taking three days as a group, spatial images of a few parameters were analyzed, from which it can be seen during the five days prior to this earthquake, the amplitude and scale of anomalies are enlarged, while the epicenter is located at the boundary of anomalous region. The anomalous tempo-spatial variation in electron density prior to the earthquake were also obtained in terms of tracing the data from revisited orbits in half a year prior to the quake.
基金Supported by the Seismic Public Welfare Scientific Research Special Appropriation Project of China(201008007)the National Natural Science Foundation of China(41004066)
文摘The ionospheric effect from solar activity can be seen as the background in the process of detecting the ionospheric precursor prior to strong earthquakes.The ionospheric variation induced by the forthcoming earthquake can be covered by the strong solar background during the period of high solar activity.The issue of how to remove the ionospheric effect from solar radiation is of outstanding significance.In this paper,a method of Empirical Mode Decomposition(EMD) is used to eliminate the solar background.As a case study,the global ionospheric map TEC before the M9.0 Tohoku earthquake on 11 March 2011 is analyzed.After the effect of solar radiation is removed using the EMD method,the precursor of the imminent earthquake is more obvious.The ionospheric anomaly had a local character and only appeared close to the earthquake epicenter while the useful signals were covered by the solar radiation background with traditional method,which implies that the EMD method is effective in eliminating solar radiation background.
基金supported by the National Natural Science Foundation of China(NSFC) Project (11373059)Shanghai Science and Technology Commission Project(12DZ2273300)Key Laboratory of Planetary Sciences,Chinese Academy of Sciences
文摘The seismo-ionospheric anomalies may provide some insights about the earthquake.However,preseismic ionospheric anomalies are still challenging.In this paper,seismo-ionospheric anomalies are investigated before the September 24,2013(Mw=7.7)Awaran(Pakistan)earthquake from GPS TEC(Total Electron Content)and COSMIC(Constellation Observing System for Meteorology,Ionosphere and Climate)data.The TEC data are showing anomalies on September 21,2013.The abnormality detected in the temporal data is about 10 TECU beyond the 30-day running median.The percentage deviation of the TEC anomaly on September 21,is 30% above the upper confidence interval.The anomalies prevail 5 in Latitude and 10 in Longitude over the epicenter.The spatial and temporal data of TEC showed anomalies in TEC from UT=08 to UT=12.In addition,the enhancement on September 21,2013 is also very significant in COSMIC data.The results of COSMIC completely agreed with GPS TEC anomalies on September 21,2013.The percentage deviation of the peak plasma frequency on September 21 is 5% of the normal distribution.The storm indices are quiet before and after the earthquake.The pre-sesimic ionospheric anomalies are most probably associated with the 2013 Mw=7.7 Awaran(Pakistan)earthquake.
基金Supported partly bv RFBR (No. 04-05-39008)the Foundation for State Support of Leading Scientific Schools of the Russian Federation (No. NSh-272.2003.5)the China-Russia Joint Research Center on Space WeatherChinese Academy of Sciences
文摘This paper analyzes the state of the ionosphere during two geomagnetic storms of a different intensity evolving in different sectors of local time in different seasons. There were used the data from a network of ionospheric stations located in the opposite longitudinal sectors of 80°-150° E and 250°-310° E.This analysis has permitted us to conclude that the detected differences in the variations of the disturbances are likely to be determined by the local time difference of the geomagnetic storm development, its intensity and by the different illumination conditions of the ionosphere.
基金supported by the National Natural Science Foundation of China (Grant Nos. 42074024, 41890813 & 41976066)the Young Talent Promotion Project of the China Association for Science and Technology。
文摘Hunga Tonga-Hunga Ha’apai climactic eruption on January 15,2022,released enormous energy that affected the ionosphere over the Pacific Rim.We analyzed ionospheric disturbance following volcanic eruptions using near-field(<1000 km),regional(1000–5000 km),and far-field(5000–12000 km) global positioning system(GPS) observations.The results indicate that the near-field ionospheric perturbation that occurred 8–15 min after the cataclysmic eruption was mainly derived from the shock wave(~1000 m/s) generated by the blast,while the low-frequency branch with long-distance propagation characteristics over the regional and the far-field was mainly associated with atmospheric Lamb waves(~330 m/s).Moreover,the amplitude of disturbance and background total electron content(TEC) are related proportionally.The intensity of the volcanic eruption and the background ionospheric conditions determine the magnitude of ionospheric responses.TEC perturbations were invisible on the reference days.Furthermore,the source location and onset time were calculated using the ray tracing technique,which confirms that the Tonga event triggered the ionospheric anomaly beyond the crater.Finally,the change in the frequency of the perturbations coincided with the arrival of the initial tsunami,implying the generation of a meteotsunami.
文摘同全球导航卫星系统(global navigation satellite system, GNSS)获取电离层总电子含量(total electron content, TEC)数据相比,传统的电离层垂测、斜测等短波段数据具有特征参数丰富、高度分辨率高、历史数据多等优点。为利用电离层垂测和斜测数据,研究地下核爆引起的电离层扰动。利用2016年1月6日朝鲜地下核试验当天的斜测、垂测数据分析电离层扰动现象。结果表明,本次地下核爆造成的行波电离层扰动为小尺度电离层扰动,传播速度为150.3~158.7 m/s。同时核爆发生后0.5 h在距离爆点421.4 km处,观测到F2层临界频率(critical frequency of the F2layer, foF2)较月中值增加了0.7 MHz,较1月5日、1月7日在协调世界时(coordinated universal time, UTC)2:00 UTC的增加了0.5 MHz,极有可能是地下核爆通过岩石圈-大气圈-电离层圈耦合机制造成电离层电子浓度增加。本文分析结果与其他文献资料非常吻合。由此可见,基于短波段电离层探测方式感知电离层扰动从而实现地下核爆炸事件的监测,是一种有效的核爆电离层效应监测手段,可与其他直接监测手段相印证,提高核爆事件监测能力。
基金supported by the Chinese Academy of Sciences(Grant No.KZZDEW-01-2)the National Natural Science Foundation of China(Grant Nos.41274162,41131066,41304126)the National Basic Research Program of China(Grant No.2011CB811405)
文摘Here we report two cases of coseismic ionospheric disturbances observed through a GPS network in China after the great Wenchuan earthquake at 06:28 UT on 12 May,2008.One is detected 7.9 min after the earthquake and had an intensive"N"shape oscillated waveform with a pronounced amplitude of about 1 TECU,which propagates approximately southward to the distance about 1000 km with the horizontal phase velocity of 600±84 m/s and the period of 9.5±1.3 min.The other is detected8.5 min after the earthquake and has an oscillated waveform more like a positive pulse with an amplitude of about 0.5 TECU,which propagates eastward to the distance about 800 km with the horizontal phase velocity of 720±59 m/s and the period of7.4±0.8 min.These two coseismic ionospheric disturbances are caused by the acoustic gravity waves excited by partial transformation of the acoustic waves originated from the energy release of the earthquake,somewhere near the epicenter.The directional preferences of these two coseismic ionospheric disturbances may be associated with the oblique geomagnetic field lines and the background winds filtering effect.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40974089 & 41131066)the Chinese Academy of Sciences (Grant Nos. KZZDEW-01-2 & KGCXZ-EW-407-2)the National Key Basic Research Program of China (Grant No. 2011CB811405)
文摘Larger-scale traveling ionospheric disturbances (LSTIDs) are studied using the total electron content (TEC) data observed from 246 GPS receivers in and around China during the medium storm on 28 May 2011. It is the first attempt to get the two-dimensional TEC perturbation maps in China. Two LSTID events are detected: one is in southwestern China before midnight propagating from low to middle latitude to the distance of about 1200 km with the phase front extending to about 500 km, and the other is in northeastern China after midnight propagating from middle to low latitudes to the distance of about 1200 km with the phase front extending to nearly 1400 km. By using the multichannel maximum-entropy method, we get the propagation parameters of these two LSTIDs. The LSTID that occurs before midnight has a higher horizontal phase velocity and a larger damping rate corresponding to the after midnight LSTID, and this may be caused by the relatively large vertical background TEC 0 and high atmospheric temperature in the southwest of China before midnight. According to the variations of magnetic H component observed in high latitudes, the source region for the after midnight LSTID is likely to be located 1400-2600 km east of 140°E and north of 42°N; the before midnight LSTID is propably excited by the atmospheric gravity waves (AGWs) generated by the Joule heating of the equatorial electrojet.
基金Supported by the Project of Ministry of Science, Technology and Innovation, Malaysia (04-01-02-SF0559)
文摘The paper examines the propagation direction and velocity of large-scale traveling ionospheric disturbances (LST1Ds) during extreme geomagnetic storms in the 23rd solar cycle (e.g., October 2003 and November 2003 storms) using GPS observations. In the analysis, the time delay between the vertical total electron content (VTEC) structures at Scott Base, McMurdo, Davis and Casey GPS stations and the distance between these stations were the main parameters in the determination of LSTIDs propagation speed and direction. The observations during October and November 2003 storms show obvious time delay between the total electron content (TEC) enhancement signatures at these stations. The time delay suggests a movement of the ionospheric disturbances from higher to lower latitudes during the October storm with a velocity of 800-1 200 m/s and poleward propagation of LSTIDs during the November storm with a ve- locity of 300-400 m/s. The equatorward or poleward expansion of LSTIDs during the October and November 2003 storms is probably caused by the disturbances of the neutral temperature occurring close to the dayside convection throat or by the neutral wind oscillation induced by atmospheric gravity waves (AGW) launched from the aurora region.
基金Supported by Russian Foundation for Basic Research (No. 04-05-39008, N02-05-64570)the China-Russia Joint Research Center on Space WeatherChinese Academy of Sciences
文摘This paper presents simulated results of the ionospheric behavior during few geomagnetic storms,which were occurred in the different seasons. The numerical model for ionosphere-plasmasphere coupling was used to interpret the observed variation of ionosphere structure. Reasons why the positive storms are dominant in the winter whereas the negative ones are dominant in the summer season present the special interest for the mid-latitude ionosphere. A theoretical analysis of the processes controlling the ionospheric response to the geomagnetic storms has showed a good agreement between the simulated results and measurements, as well as the crucial role of the neutral composition variations to fit the calculated and the observed ionospheric parameters.