Electromagnetic Waves Induced By Earthquakes And Geomagnetic Storms In Ionosphere

The near-Earth space is a complex system comprised byseveral dynamically coupled layers including lithosphere,atmosphere and ionosphere,etc.In this system,earthquake events are considered as the most destructive disaster for human among other natural disaster events.Due to the variationof tectonic stress,the active fault zone with the long-term mutual compression and the energy accumulation,eventually sudden releases a great amount of energy into the lithosphere within a few seconds.During the long-term earthquake preparation beforethe occurrence of the main shock,certain anomalous changes of multiple signals,such as thermal and electromagnetic radiations in the surface(including the ocean),can couple into theatmosphere and ionosphere through the geodynamic processes.In order to interpret the phyiscal mechanism,the lithosphere-atmosphere-ionosphere Coupling(LAIC)model has been paid great attention,and serveral coupling channels were put forward by previous studies.Although the it is still not clearly understood,but it brings potentials of making breakthrough for earthquake prediction science.Recently the Low-Earth-Orbit(LEO)satellites are playing an increasingly important role with the rapid development of satellite technology,for example,the China Seismo-electromagnetic Satellite(CSES),provides a good opportunity for the study of the lithosphere-atmosphereionosphere coupling mechanism with more detailed observation about the earth.Based on the development of satellite observation technology and scientific application research,some convincing research results have been obtained for the mechanism of lithosphereatmosphere-ionosphere-coupling,but there is still a need to accumulate earthquake cases to study meanwhile improving the observation techniques and analysis methods.The orbit space of LEO satellite suffers from electromagnetic disturbances not only from the Earth,but from the solar activies and corresponding geomagnetic storms/substorms.So as to have an overall understanding of the geospace electromagnetic environment,it is necessary to have comprehensive studies on the electromagnetic waves related with both strong earthquakes and non-earthquake sources in the geospace.This is the main objective of this dissertation.In this thesis,we utilized the electromagnetic observations from DEMETER and CSES satellite to investigate electromagnetic waves in the ionosphere.Firstly,we developed a wave vector analysis of tool of CSES's waveform data,which was verified by DEMETER's data.Then,We made a detailed analysis of the ELF electromagnetic wave characteristics in the ionospheric caused by typical earthquakes.Lastly,we studied the characteristics of ELF/VLF electromagnetic waves during strong magnetic storms byusing CSES satellite data in 2018.Following are our main results:1.The wave vector analysis tool for the electromagnetic waves of CSES satellite.We mainly developed a wave vector analysis tool for the electromagnetic waves recorded by the CSESsatellite,which provides the functions of waveform spectrum transform,singular value decomposition(SVD)and Poynting flux methods.According to the typical electromagnetic wave events recorded by CSES satellite,such as lightning induced whistler-mode waves,quasi-periodic emissions,ionospheric hiss waves,we applied the tool to analyze propagation feature of the waves and preliminarily discussed the spectral features and propagation parameters of these waves.We also validated the algorithm code by comparison with DEMETER's observations,which results confirm that the CSES's has good performance on the electromagnetic field observations.This tool developed in this study can be directly applied to the routine data processing and scientific application of CSES satellite.2.ELF/VLF Electromagnetic wave disturbances duringstrong earthquakes.The abnormal ELF electromagnetic emissions at frequency from 300 to 800 Hz during the 2010 Apr.6 Ms 7.8 Sumatra earthquake was found this studies The variation patterns of same orbit trajectories computed from the revisiting orbits during Aug.2009 to May.2010 indicate that the magnetic field intensity at ELF [300-800 Hz] appeared abnormal enhancement 10 days to 3 days before the main shock,compared to the relatively smooth variation level during the quiet seismic activity time.We further computed the wave propagation parameters by using the burst-mode waveform data,and results show that DEMETER satellite recorded some portions of emissions mainly below 800 Hz propagating upward to satellite's position over the epicenter zone 10 and 6 days before the main shock.The perturbations amplitude of magnetic field at ELF[300 to 800 Hz] relative to the long-term background map over the seismic zone show that during the earthquake impending time interval from Mar.21 to Apr.6,2010,there are indeed abnormal enhancement mainly over the northeast area of the epicenter.3.The ELF/VLF electromagnetic emissions during during magnetic storm.Using the electromagnetic field observation data of the CSES satellite,we studied the electromagnetic emissions and disturbance during the strong magnetic storm(Dst?-174 n T)on August 26,2018.The research results show that the overall payloads of the CSES satellite have a good consistency during the strong geomagnetic storm.We observed strong electromagnetic wave activitiesin the ionosphere during this magnetic storm,including the quasi-periodic emissions and hiss enhancement.The period of the quasiperiodic radiation is in the range of 1s-20 s.Wave vector analysis proves that this quasiperiodic emissions are typical right-handed whistler-mode with the propagation angle relative to the background magnetic field about 30-50°,and the Poynting flux flow is mainly concentrated in the direction of the perpendicular direction of magnetic field.The hiss owns similar type of wave vector propagation characteristics with the quasiperiodic emissions:right-handed polarized and have good planerity.The electromagnetic waves below the ELF/VLF 3k Hz during the main phase of the magnetic storm are significantly enhanced during the entire magnetic storm.The enhancement of electromagnetic waves is generally in the range of L shell range from 2-4,and recovers to the level before the magnetic storm in about 2-3 days in the recovery phase,while waves at frequencies above 3 k Hz are mainly strengthened in the initial short period of the main phase and the recovery phase and the duration of the enhancement becomes shorter with frequency increases.Through observations on the day and night sides of the magnetic component power spectral density,we found that in this magnetic storm,the strength of the ELF/VLF fluctuation enhancement on the day side and the duration of the fluctuation disturbance between the same frequency bands are much higher than the night side.