An attempt to inverse the ionospheric sporadic-E layer critical frequency based on the COSMIC radio occultation data

Abstract

Ionospheric sporadic E layer refers to localized thin irregularity with enhanced plasma density appearing in the height range of ionospheric E layer (∼90–130 km). The much higher electron density in the sporadic E layer than the background ionosphere would cause sudden TEC enhancement in the occultation TEC profile. A wavelet decomposition and reconstruction method is applied to extract the TEC fluctuation in this paper, and then Smax index is defined to represent the intensity of the sudden TEC enhancement. Smax index is compared with sporadic E critical frequency (foEs) observed by the ionosonde. The results show a well linear correlation between them with mean correlation coefficient about 0.7. Thus, an empirical linear model is established to inverse the foEs. The monthly/hourly mean values and global distribution of sporadic E intensity and occurrence ratio are calculated using this method based on the COSMIC occultation data from 2007 to 2011. The statistical analysis results indicate that it is feasible to inverse the foEs based on the occultation TEC profile data and the inversion results can be applied to the long-term global variations of sporadic E investigations.