Analysis Of Disturbance Characteristics Of Preseismic Ionospheric TEC Anomalies

Earthquake is a natural disaster phenomenon from the accumulation of energy to the sudden release.Its incubation process is very complex,including the accumulation of stress,friction,charge generation and chemical reaction and other microscopic processes.These processes are converted into some precursor information and recorded by human beings,which can be used as reference to advance the development of earthquake prediction field.After the Alaska earthquake in 1960s,it was found that the ionospheric disturbance occurred before the earthquake.Therefore,the seismic ionospheric effect has become a hot research direction of many scholars.Based on this direction,this paper introduces the basic structure of the ionosphere,the formation reasons and the disturbance factors.In this paper,two main theories about the earthquake ionospheric effect are described,and representative models and previous results are listed.Then,the variation characteristics of ionospheric Total Electron Content(TEC)on time and space scales were analyzed by using GIM data,and the criteria and methods for judging whether the TEC sequence is abnormal were derived.Finally summarizes the existing anomaly detection algorithm and choose the appropriate method is applied to the specific of earthquake examples,analysis and near the epicenter area may be caused by the earthquake abnormal TEC space-time distribution characteristics,the probability of statistical anomaly,in order to present research results to make a summary before the earthquake anomaly distribution characteristics and existing theory as the theoretical basis to discuss the result of the part characteristics.The main contents and conclusions are as follows:1)The formation reason,basic structure and other background knowledge of the ionosphere are described.Effects of solar and geomagnetic activities on the ionosphere and their corresponding environmental indices.This paper summarizes the existing representative theories of the coupling mechanism of lithosphere-atmosphere-ionosphere and the models of different theories.This paper reviews the physical and chemical processes such as gas release,atmospheric oscillation and particle deposition during seismogenic period,and integrates the representative model of seismic ionospheric effect and the propagation path of ionospheric disturbance caused by it.2)Study on spatiotemporal variation characteristics of ionospheric TEC.Based on the GIM data provided by CODE,the characteristics of TEC annual variation,seasonal variation,diurnal variation and spatial variation in 11 years were analyzed.The results show that TEC is highly correlated with solar activity,and there are obvious four seasons in high solar activity years.When the solar activity level is high and the solar flux in winter is higher than the summer level of the same year,the TEC winter anomaly will occur.The difference of adjacent latitude TEC is higher than that of adjacent longitude TEC.3)Analysis of earthquake cases and statistical results.The sliding standard deviation method was used to analyze the anomalies of the earthquake cases in Ya 'an,Yutian and Jiuzhaigou by using GIM data combined with environmental index.The TEC anomalies that may be related to earthquakes were detected in all of them,and the range and amplitude of the anomalies were listed one by one.In 219 before the earthquake epicenter of the earthquake TEC disturbance analysis results,combining the existing of the academic conclusion,summed up the TEC anomaly distribution mainly concentrates in less than a week before,the unusual form of plus or minus is possible,give priority to with positive anomaly,duration is more than 2 hours to the equator and the spatial distribution of the side is the state of the conjugate characteristics.Based on the theory of electric field,the physical mechanism of abnormal attribute and orientation is explained.Based on the experimental results,this paper suggests that the ionosphere TEC and earthquake has a certain relevance,monitoring the ionosphere for earthquake precursor information research is possible,but seismic ionospheric effects involved process is very complicated,containing numerous reactions need to further explore,based on this paper.Based on this,we should combine more monitoring data and more perfect model to further study the coupling relationship between them.