An Abel inversion method assisted by an improved IRI model for GPS ionospheric radio occultation data
Presenter:
Mengjie Wu
Shanghai Astronomical Observatory, Chinese Academy of Sciences
Shanghai Astronomical Observatory, Chinese Academy of Sciences
Talk
The most significant error of the radio occultation (RO) ionospheric retrieval is brought by the spherical symmetric assumption of electron density in Abel inversion. We developed an improved inversion method that attaches additional horizontal constraints based on a background model in Guo et al. (2015, https://doi.org/ 10.1016/j.jastp.2014.12.008), and found the effect of the method depends greatly on the accuracy of the background model. In this study, an improved ionospheric model, which applies RO-based F2-layer parameters and an adaptive topside model into the International Reference Ionosphere (IRI), is employed as a new choice of background model. The improved inversion is evaluated in several aspects in the mid- and low-latitudinal regions during equinox season (from March 19 to April 18 in 2008 and 2012) and throughout the year. Results show that the artificial plasma caves underneath the equatorial ionization anomaly (EIA) crests caused by Abel inversion is to some extends eliminated during the daytime, and the negative electron densities in the E layer are also reduced by the improved method. The comparison between COSMIC events and co-located incoherent scatter radar (ISR)/ionosonde observations indicates comparable accuracy of both methods. Moreover, the Global Ionosphere Maps (GIM) is introduced as true reference of the vertical total electron density content (VTEC). The mean VTEC errors derived through the improved inversion method are less than that of Abel inversion in the global scope.
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