Characteristics Of Equatorial Ionization Anomaly In The Americas Sector From Ground-Based IGS Networks

The upper atmosphere is ionized under the influence of solar radiation and various cosmic rays,and the ionization region of the atmosphere is called the ionosphere.The ionosphere is an important part of the earth's atmosphere.It plays a vital role in radio wave propagation,which can make radio wave refraction,reflection and scattering.Therefore,it is very important to study the structure of the ionosphere and its related variation characteristics.This article is based on the global satellite navigation observation group(International GNSS Service,IGS)to provide the foundation of a GPS satellite observation data,the americas(near 300 ° E longitude)different hemisphere low-latitude region of ionospheric Total Electron Content(Total Electron Content,TEC)and correlation analysis,changes in the characteristics of concrete,including the americas low latitude ionosphere TEC day change,seasonal change,change year by year,and the different latitude and longitude will be the ionosphere TEC data processing,The intensity of Equatorial Ionization Anomaly(EIA)in different latitudes and the asymmetry between the northern and southern regions were compared and analyzed.The structure and main research results of this paper can be summarized as follows:Firstly,this paper introduces the basic concept of the ionosphere,its formation reasons,structural stratification and abnormal phenomena.The data source and format selected in this paper are explained,and the specific method for calculating the total electron content in the ionosphere is expounded.Secondly,based on the ionospheric observation data obtained from ground-based GPS satellites,the TEC values of the selected ground-based stations were analyzed and calculated,and then the variation characteristics of TEC in different hemispheres,latitudes and longitudes were compared and analyzed.In the southern and northern hemisphere,the low latitude ionospheric TEC varies with time,season and year,and the variation range(maximum minus minimum)of TEC value is larger in spring and autumn than in summer and winter.The minimum value of TEC is generally around5:00 LT,and the maximum value is generally around 13:00 LT.The TEC value is directly proportional to the solar activity intensity.The ionospheric TEC in low latitude varies with latitude and longitude,from the perspective of the northern and southern regions,the variation range of TEC near 15° in the southern hemisphere is more stable than that near 25°,while it is just the opposite in the northern hemisphere.The variation order of TEC value in low latitude area is as follows: geomagnetic northern latitude 25° >geomagnetic northern latitude 15°> geomagnetic southern latitude 15°> geomagnetic southern latitude 25°;In addition,the variation range of TEC varies with longitude,for example,the variation range of TEC in 285°E longitude area is generally greater than that in 300°E longitude area.Thirdly,the calculated low latitude ionospheric TEC data in different hemispheres are used to analyze the variation characteristics of equatorial ionization anomalies over the American region with time,season and year.The results show that the intensity of EIA and the asymmetry of the northern and southern hemispheres vary significantly with time,season and year.The intensity of EIA reached a maximum in spring and autumn,and a minimum in winter.The intensity of EIA decreases with the decrease of solar activity.EIA hemispheric asymmetry reaches maximum from May to August,and minimum in spring/autumn.The variation characteristics of EIA hemispheric asymmetry with solar activity are not significant.In addition,the variation characteristics of EIA intensity and hemispheric asymmetry are also latitude dependent.The hemispheric asymmetry at ±25° of geomagnetic latitude is more significant than that at ±15° of geomagnetic latitude,and the duration of asymmetry near ±25° is longer than that near ±15°.Finally,two magnetic storms in 2016 and 2018 were selected to analyze the variation characteristics of EIA intensity and south-northern hemisphere asymmetry during magnetic disturbances,and it was found that magnetic disturbances had significant effects on both EIA intensity and south-northern hemisphere asymmetry.During a geomagnetic storm,the intensity of EIA may increase or be suppressed.EIA hemispheric asymmetry may become significant or may be reduced.The results of this paper are helpful for us to get more familiar with the characteristics of the low latitude ionosphere in the Americas region,help us to understand the structure and characteristics of the global ionosphere in depth,and also lay a certain foundation for the construction of the regional and global background ionosphere model,which has certain reference value and practical application value.