Statistical analysis on spatial correlation of ionospheric day-to-day variability by using GPS and Incoherent Scatter Radar observations

摘要

In this paper, the spatial correlations of ionospheric day-to-dayvariability are investigated by statistical analysis on GPS and IncoherentScatter Radar observations. The meridional correlations show significant(>0.8) correlations in the latitudinal blocks of about 6 degrees size onaverage. Relative larger correlations of TEC's day-to-day variabilities canbe found between magnetic conjugate points, which may be due to thegeomagnetic conjugacy of several factors for the ionospheric day-to-dayvariability. The correlation coefficients between geomagnetic conjugatepoints have an obvious decrease around the sunrise and sunset time at the upperlatitude (60°) and their values are bigger between the winter and summerhemisphere than between the spring and autumn hemisphere. The time delay ofsunrise (sunset) between magnetic conjugate points with a high dip latitude isa probable reason. Obvious latitude and local time variations of meridionalcorrelation distance, latitude variations of zonal correlation distance, andaltitude and local time variations of vertical correlation distance aredetected. Furthermore, there are evident seasonal variations of meridionalcorrelation distance at higher latitudes in the Northern Hemisphere and localtime variations of zonal correlation distance at higher latitudes in theSouthern Hemisphere. These variations can generally be interpreted by thevariations of controlling factors, which may have different spatial scales.The influences of the occurrence of ionospheric storms could not be ignored.Further modeling and data analysis are needed to address this problem. Wesuggest that our results are useful in the specific modeling/forecasting ofionospheric variability and the constructing of a background covariance matrixin ionospheric data assimilation.